HK40081811A - Methods for producing optical effect layers comprising magnetic or magnetizable pigment particles - Google Patents

Description

Method for producing an optical effect layer comprising magnetic or magnetizable pigment particles

Technical Field

The present invention relates to the field of magnetic field generating devices and methods for producing Optical Effect Layers (OEL) comprising magnetically oriented platy magnetic or magnetizable pigment particles. In particular, the present invention provides a magnetic field generating device and method for magnetically orienting plate-like magnetic or magnetizable pigment particles in a coating to produce an OEL, and the use of said OEL as an anti-counterfeiting means on security documents or security articles as well as for decorative purposes.

Background

It is known in the art to use inks, compositions, coating films or layers comprising oriented magnetic or magnetizable pigment particles, in particular also optically variable magnetic or magnetizable pigment particles, to produce security elements, for example in the field of security documents. Coatings or layers comprising oriented magnetic or magnetizable pigment particles are disclosed in, for example, US 2,570,856; US 3,676,273; US 3,791,864; US 5,630,877 and US 5,364,689. Coating films or layers comprising oriented magnetic color-changing pigment particles, which lead to particularly attractive optical effects, which can be used for protecting security documents, have been disclosed in WO 2002/090002 A2 and WO 2005/002866 A1.

For example, security features for security documents may be generally classified as "covert" security features on the one hand and "overt" security features on the other hand. The protection provided by covert security features relies on the notion that such features are difficult to detect, typically requiring specialized instrumentation and knowledge for detection, while "overt" security features rely on the notion that they are readily detectable with an independent (unaided) human sense of sight, e.g., such features may be visually and/or tactilely detectable, but still difficult to produce and/or reproduce. However, the effectiveness of overt security features depends largely on their ease of identification as security features.

The magnetic or magnetizable pigment particles in the printing ink or coating film can produce magnetically induced images, designs and/or patterns by inducing a local orientation of the magnetic or magnetizable pigment particles in the not yet hardened (i.e. wet) coating film by applying a correspondingly structured magnetic field, followed by hardening of the coating film. 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 in, for example, 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 667B1; US 2002/0160194; US 2004/0009308; EP 0 710 A1; WO 2002/09002A2; WO 2003/000801 A2; WO 2005/002866 A1; WO 2006/061301 A1. In this way, a highly forgery-proof magnetically induced pattern can be produced. The security element in question can only be produced by using both magnetic or magnetizable pigment particles or corresponding inks, and specific techniques for printing said inks and orienting said pigments in the printed inks.

In order to protect security documents or articles containing magnetically induced images from premature detrimental effects of soil and/or moisture during and over the time of use, protective varnishes have been used in practice. The protective varnish is applied as a continuous layer over the magnetically induced image that has been prepared and dried/cured.

WO 2011/012520 A2 discloses a transfer foil comprising a coating in the form of a design comprising optically variable magnetic pigments representing the orientation of an image, indicia or pattern. The transfer foil may further comprise a top coat layer, wherein the top coat layer is applied before applying the layer comprising optically variable magnetic pigments. The method for producing the transfer foil comprises a) the steps of applying a top coat layer, hardening/curing the top coat layer, and b) applying a layer comprising 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 need to exhibit individualized variable markings.

EP1 641 b 624 B1, EP1 937 b 415 B1 and EP2 155 498 B1 disclose devices and methods for magnetically transferring labels into coating compositions which have not yet been hardened (i.e. wetted) and which comprise magnetic or magnetizable pigment particles, thereby forming Optical Effect Layers (OELs). The disclosed method enables the production of security documents and articles having a consumer specific magnetic design. However, the disclosed magnetic devices are prepared to meet specific designs and cannot be modified if the design needs to be changed from one article to another, and therefore, the method is not suitable for producing OELs that need to exhibit individualized variable markings.

EP 3 170 566 B1 and EP 3 459 758 A1, EP2 542 B1 disclose different methods for producing variable marks on optically variable magnetic inks. However, the method requires the use of special equipment, such as a photomask or a laser.

To produce variable information on security documents or articles with Magnetic properties, ink jet inks (inkjet Ink) containing Magnetic particles have been developed to allow Magnetic Ink Character Recognition (MICR). However, the inkjet inks face different challenges, in particular those related to shelf-life stability of the ink, ink printability, heterogeneous magnetic ink deposition and printhead clogging. EP2 223 976 B1 discloses a method for producing a document containing MICR features, wherein the method comprises the steps of: applying a pattern of curable ink comprising a gelling agent onto a substrate by ink jetting, cooling the ink to below the gel temperature of the ink, applying a magnetic material onto the ink and finally curing the ink. Alternatively, toners containing magnetic particles have also been developed and are disclosed, for example, in US 10,503,091 B2 and S10,359,730 B2. However, special dedicated equipment is required to print these toners.

Therefore, there is a need for a method of producing in a versatile manner and on an industrial scale customized optical effect layers exhibiting more than one marking, which optical effect layers exhibit a pro-ocular effect. Furthermore, the method should be reliable, easy to implement and capable of operating at high production speeds.

Disclosure of Invention

It is therefore an object of the present invention to overcome the disadvantages of the prior art. This is achieved by providing a method for producing an Optical Effect Layer (OEL) exhibiting one or more marks (x 30) on a substrate (x 20), said method comprising the steps of:

a) Applying a radiation curable coating composition comprising non-spherical magnetic or magnetizable pigment particles on a surface of a substrate (x 20), the radiation curable coating composition being in a first liquid state, thereby forming a coating layer (x 10);

b) Exposing the coating (x 10) to a magnetic field of a magnetic field generating device, thereby orienting at least a portion of the magnetic or magnetizable pigment particles;

c) After step b), applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more markings (x 30), and

d) Simultaneously with or after step c), at least partially curing the coating (x 10) and the one or more markers (x 30) with a curing unit (x 50).

In a preferred embodiment, step b) of exposing the coating (x 10) is performed such that at least a part of the magnetic or magnetizable pigment particles are uniaxially oriented. In another preferred embodiment, step b) of exposing the coating (x 10) is performed such that at least a part of the magnetic or magnetizable pigment particles is 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, rotogravure printing, pad printing and flexographic printing.

In a preferred embodiment, step c) of applying the topcoat composition is carried out by a non-contact fluid microdispensing technique, preferably by an ink jet printing process.

Also described herein are Optical Effect Layers (OELs) produced by the methods described herein, and security documents and decorative elements and objects comprising one or more layers of the optical OELs described herein.

Also described herein is a method of manufacturing a security document or decorative element or object comprising: a) Providing a security document or a decorative element or object; and b) providing an optical effect layer such as those described herein, in particular such as those obtained by the methods described herein, such that it is comprised by a security document or decorative element or object.

The methods described herein advantageously use two compositions, wherein the two compositions are applied to each other in a wet-on-wet (wet-on-wet) state. In particular, the method according to the invention enables the production of Optical Effect Layers (OEL) exhibiting more than one marking in a versatile manner, which can be easily implemented on an industrial scale at high production speeds. Two compositions used in the method described herein include as a first composition a radiation-curable coating composition applied on a substrate (x 20) comprising non-spherical magnetic or magnetizable pigment particles, and as a second composition a topcoat composition applied on top of and partially overlapping (i.e. overlapping in at least one region) with the radiation-curable coating composition comprising pigment particles, and which is applied in the form of one or more indicia while the radiation-curable coating composition is still in a wet, unpolymerized state.

The present invention provides a reliable and easy to implement method for producing a pro-ocular Optical Effect Layer (OEL) exhibiting one or more of the indicia described herein. The disclosed method advantageously enables the production of security documents and articles having a consumer-specific magnetic design and also exhibiting more than one marking in a versatile, on-line variable, easy to implement and highly reliable manner without the need to customize the magnetic assembly for orienting the non-spherical magnetic or magnetizable pigment particles for each variable or personalized marking and for each consumer-specific Optical Effect Layer (OEL). The present invention also provides a reliable and easy way to implement a method for producing a pro-ocular Optical Effect Layer (OEL) exhibiting one or more indicia comprising variable halftones as described herein.

Drawings

The process described herein for producing an Optical Effect Layer (OEL) exhibiting more than one mark (x 30) on a substrate (x 20) described herein is now described in more detail with reference to the figures and specific embodiments, wherein

Fig. 1 schematically shows flake-like pigment particles.

Fig. 2A schematically illustrates a method according to the present invention for producing an Optical Effect Layer (OEL) exhibiting more than one marking (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating means (B1) thereby uniaxially orienting 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 indicia (230); and step d): the coating (210) and the one or more indicia (230) are at least partially cured with a curing unit (250).

Fig. 2B schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting 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 indicia (230); and a step d): the coating (210) and the one or more indicia (230) are at least partially cured with a curing unit (250).

Fig. 2C schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises a step b 1): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles; simultaneously with part of step b 1), simultaneously with or after step b 1), step b 2): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to uniaxially reorient-ate at least a portion of the lamellar magnetic or magnetizable particles; after step b 2), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more indicia (230); and step d): the coating (210) and the one or more indicia (230) are at least partially cured with a curing unit (250).

FIG. 2D-1 schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting more than one marking (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating means (B1) thereby uniaxially orienting 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 indicia (230); simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first regions of the coating (210) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally to fix at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second regions of the coating (210) and optionally one or more second regions of the topcoat film (230) remain unexposed to the irradiation; after step x), step y): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); and step d): the coating (210) and the one or more indicia (230) are at least partially cured with a curing unit (250).

Fig. 2D-2 schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting 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 indicia (230); simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first areas of the coating (210) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally fixing at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second areas of the coating (210) and optionally one or more second areas of the topcoat film (230) remain unexposed to the radiation; after step x), step y): exposing the coating (210) to a magnetic field of a second magnetic field generating means (B2) so as to uniaxially orient at least a part of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); and d) at least partially curing the coating (210) and the one or more marks (230) with a curing unit (250).

Fig. 2D-3 schematically illustrate a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises the step b 1): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles; after step b 1), step b 2): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to reorient at least a portion of the flaky magnetic or magnetizable particles uniaxially; after step b 2), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more indicia (230); simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first areas of the coating (210) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally fixing at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second areas of the coating (210) and optionally one or more second areas of the topcoat film (230) remain unexposed to the radiation; after step x), step y): exposing the coating (210) to the magnetic field of a third magnetic field generating means (B3) to uniaxially reorient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); and d) at least partially curing the coating (210) and the one or more marks (230) with a curing unit (250).

FIG. 2E-1 schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more indicia (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating means (B1) thereby uniaxially orienting at least a portion of the magnetic or magnetizable pigment particles; simultaneously with part of step b) or after step b), step x): selectively at least partially curing one or more first regions of the coating (210) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally to fix at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second regions of the coating (210) and optionally one or more second regions of the topcoat film (230) remain unexposed to the irradiation; after step x), step y): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to uniaxially reorient-ate at least a part of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); after step y), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more indicia (230); and d) at least partially curing the coating (210) and the one or more marks (230) with a curing unit (250).

Fig. 2E-2 schematically illustrates a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises a step b): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles; simultaneously with part of step b) or after step b), step x): selectively at least partially curing one or more first regions of the coating (210) of the radiation curable coating composition of step b) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally to fix at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second regions of the coating (210) and optionally one or more second regions of the topcoat film (230) remain unexposed to the radiation; after step x), step y): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); after step y), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more indicia (230); and d) at least partially curing the coating (210) and the one or more marks (230) with a curing unit (250).

Fig. 2E-3 schematically illustrate a method according to the invention for producing an Optical Effect Layer (OEL) exhibiting one or more marks (230) on a substrate (220). The method comprises a step b 1): exposing the coating (210) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles; simultaneously with step b 1), partially simultaneously or after step b 1), step b 2): exposing the coating (210) to the magnetic field of a second magnetic field generating means (B2) to uniaxially orient at least a portion of the flaky magnetic or magnetizable particles; simultaneously with part of step b 2) or after step b), step x): selectively at least partially curing one or more first regions of the coating (210) of the radiation curable coating composition of step b) with a selective curing unit (260) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, and optionally to fix at least a portion of the topcoat film (230) in the position and orientation they adopt, such that one or more second regions of the coating (210) and optionally one or more second regions of the topcoat film (230) remain unexposed to the radiation; after step x), step y): exposing the coating (210) to the magnetic field of a third magnetic field generating means (B3) to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (210); after step y), step c): applying a topcoat composition over the coating (210), wherein the topcoat composition is applied in the form of one or more indicia (230); and d) at least partially curing the coating (210) and the one or more marks (230) with a curing unit (250).

FIG. 3 schematically shows a magnetic field generating device for biaxially orienting magnetic or magnetizable pigment particles in a coating (310) on a substrate (320)

Fig. 4A-F schematically illustrate a comparative method for producing an Optical Effect Layer (OEL) on a substrate (420).

FIGS. 5A-E show pictures of OEL prepared according to the method of the present invention (E1-E21) and OEL prepared according to the comparative method (C1-C11) at two viewing angles (-30 deg. and +30 deg.).

Detailed Description

Definition of

The following definitions are set forth to illustrate the meaning of the terms discussed in the specification and set forth in the claims.

The term "at least one" as used herein is intended to define one or more than one, such as one or two or three.

As used herein, the terms "about" and "substantially" mean that the amount or value in question may be at or near the specified value. In general, the terms "about" and "substantially" denoting a particular value are intended to denote a range within ± 5% of that value. As an example, the phrase "about 100" means a range of 100 ± 5, i.e., a range from 95 to 105. In general, when the terms "about" and "substantially" are used, it is contemplated that similar results or effects according to the present invention may be obtained within ± 5% of the specified value.

The term "substantially parallel" means no more than 10 ° from parallel alignment and the term "substantially perpendicular" means no more than 10 ° from perpendicular alignment.

As used herein, the term "and/or" means that all or only one of the elements of the set may be present. For example, "a and/or B" shall mean "only a, or only B, or both a and B". In the case of "a only", the term also covers the possibility that B is absent, i.e. "a only, but no B".

The term "comprising" as used herein is intended to be non-exclusive and open-ended. Thus, for example, a coating composition comprising compound a may comprise other compounds than a. However, the term "comprising" also covers as its specific embodiments the more restrictive meanings of "consisting essentially of 8230; …" consisting of 8230; 〓 "consisting of 8230;" so that, for example, "fountain solution comprising A, B, and optionally C" may also consist either (essentially) of A and B, or (essentially) of A, B, and C.

The term "optical effect layer" (OEL) as used herein means a coating comprising 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) thereby forming 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 which may be applied preferentially, but not exclusively, by a printing process. The coating composition comprises the plate-like magnetic or magnetizable pigment particles described herein and a binder described herein.

As used herein, the term "wet" refers to an uncured coating, such as a film coating in which the plate-like magnetic or magnetizable pigment particles are still able to change their position and orientation under the influence of an external force acting on them.

The term "security document" refers to a document that is typically protected from counterfeiting or fraud by at least one security feature. Examples of security documents include, without limitation, documents of value and commercial goods of value.

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

Where the present description refers to "preferred" embodiments/features, combinations of such "preferred" embodiments/features should also be considered disclosed, as long as such "preferred" embodiments/features combinations are technically meaningful.

The present invention provides a method for producing an Optical Effect Layer (OEL) exhibiting one or more labels (x 30) on a substrate (x 20), wherein the OEL is based on magnetically oriented platy magnetic or magnetizable pigment particles, and further exhibits one or more labels (x 30).

The process described herein comprises step a): applying a radiation curable coating composition comprising non-spherical magnetic or magnetizable pigment particles as described herein on a surface of a substrate (x 20) as described herein, thereby forming a coating (x 10) as described herein, said composition being in a first liquid state which allows it to be applied as a layer and in an as yet uncured (i.e. wet) state, wherein the pigment particles may move and rotate within said layer. Since the radiation curable coating composition described herein is to be provided on a surface of a substrate (x 20), the radiation curable coating composition comprises at least a binder material and magnetic or magnetizable pigment particles, wherein the composition is in a form that allows it to be processed on the desired printing or coating equipment. Preferably, said step a) is performed by a printing method, preferably selected from the group consisting of screen printing (screen printing), rotogravure printing, flexographic printing, intaglio printing (also known in the art as engraved copperplate printing, engraved steel die printing), pad printing, and curtain coating, more preferably selected from the group consisting of gravure printing, screen printing, rotogravure printing, pad printing, and flexographic printing, still more preferably screen printing, rotogravure printing, pad printing, and flexographic printing.

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

The non-spherical magnetic or magnetizable pigment particles described herein are defined as having a non-isotropic reflectivity (non-isotropic reflectivity) for 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 that is reflected by the particle into a particular (viewing) direction (a second angle) is a function of the orientation of the particle, i.e. a change in the orientation of the particle relative to the first angle can result in a reflection of different magnitude (magnitude) into the viewing direction. Preferably, the non-spherical magnetic or magnetizable pigment particles described herein have a non-isotropic reflectivity for incident electromagnetic radiation in a part or all of the wavelength range from about 200 to about 2500nm, more preferably from about 400 to about 700nm, such that a change in orientation of the particles results in a change in reflection by the particles to a particular direction. As known to those skilled in the art, the magnetic or magnetizable pigment particles described herein differ from traditional pigments in that the traditional pigment particles exhibit the same color and reflectivity, regardless of particle orientation, whereas the magnetic or magnetizable pigment particles described herein exhibit reflection or color, or both, depending on particle orientation.

For embodiments of the methods described herein, wherein step b) or b 1) is performed: exposing the coating (X10) to the magnetic field of the magnetic field generating means described herein, thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles, at least a portion of the non-spherical magnetic or magnetizable pigment particles described herein, desirably consisting of platelet-shaped magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the main plane of extension of the particles. In contrast to acicular pigment particles, which may be considered as one-dimensional particles, platelet-shaped pigment particles have an X-axis and a Y-axis defining the main plane of extension of the particle. In other words, flake-like pigment particles can be considered as two-dimensional particles due to the large aspect ratio of their size as shown in fig. 1. As shown in fig. 1, flake-like pigment particles can be considered as two-dimensional structures in which dimensions X and Y are substantially larger than dimension Z. Flake-like pigment particles are also known in the art as flat particles or flakes (flakes). Such pigment particles may be described as: the major axis X corresponds to the longest dimension across the pigment particle and the second axis Y, perpendicular to X, is also located within the pigment particle.

The method described herein comprises a step b) of exposing the coating (x 10) to the magnetic field of the magnetic field generating device described herein, thereby orienting at least a part of the magnetic or magnetizable pigment particles. According to one embodiment, step b) is performed such that at least a part of the magnetic or magnetizable pigment particles described herein are uniaxially oriented. According to another embodiment, step b) is performed such that at least a part of the plate-like magnetic or magnetizable pigment particles, preferably at least a part of the plate-like magnetic or magnetizable pigment particles, are biaxially oriented such that their X-axis and Y-axis are substantially parallel to the substrate surface. For embodiments in which the method described herein comprises the step of exposing the coating (x 10) to the magnetic field of the magnetic field generating means described herein, thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles, the coating (x 10) may be exposed to said magnetic field generating means more than once.

During the herein described magnetic orientation of the magnetic or magnetizable pigment particles (step b)), the substrate (x 20) bearing the coating (x 10) may be disposed on a non-magnetic support plate (x 40) made of one or more non-magnetic materials.

The position of the magnetic field generating means during the herein described magnetic orientation of the magnetic or magnetizable pigment particles (step b)) is not limited and depends on the choice and design of the magnetic orientation pattern to be generated. Thus, the location of the magnetic field generating means (B1, B2, B3) in fig. 2 and 4 is for illustrative purposes only and is not limiting. The magnetic field generating means (B1, B2, B3) in fig. 2 and 4 may be placed below the substrate (x 20) or above the coating (x 10) depending on the choice and design of the magnetic orientation pattern to be generated.

In contrast to uniaxial orientation, in which the magnetic or magnetizable pigment particles are oriented in such a way that only their main axes are constrained by a magnetic field (constraint), biaxial orientation means that the platelet-shaped magnetic or magnetizable pigment particles are oriented in such a way that their two main axes are constrained. That is, each flake-like 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 long and short axes of the flake-like magnetic or magnetizable pigment particles are each oriented according to a magnetic field. Effectively, this results in adjacent plate-like magnetic pigment particles being spatially close to each other substantially parallel to each other. In other words, biaxial orientation aligns the planes of the platelet-shaped magnetic or magnetizable pigment particles such that the planes of the pigment particles are oriented substantially parallel with respect to the planes of adjacent (in all directions) platelet-shaped magnetic or magnetizable pigment particles. The magnetic field generating device and method described herein allow the flaky magnetic or magnetizable pigment particles described herein to be biaxially oriented such that the flaky magnetic or magnetizable pigment particles form a flaky structure whose X-axis and Y-axis are preferably substantially parallel to the surface of the substrate (X20) and planarized in the two dimensions.

Suitable magnetic field generating means for uniaxially orienting the magnetic or magnetizable pigment particles described herein are not limited and include, for example, dipole magnets, quadrupole magnets, and combinations thereof. The following devices are provided herein as illustrative examples.

The optical effect, known as the flip-flop effects (also known in the art as the switching effect), comprises a first printed section and a second printed section separated by a transition section, wherein the pigment particles are aligned parallel to a first plane in the first section and the pigment particles in the second section are aligned parallel to a second plane. Methods and magnets for producing said effect are disclosed in, for example, US 2005/0106367 and EP 1819 525B1.

An optical effect known as the "rolling-bar effect" as disclosed in US 2005/0106367 can also be produced. The "rolling bar" effect is based on simulating the orientation of pigment particles across the curved surface of a coating film. The viewer sees a specular reflection region that moves away from or towards the viewer as the image is tilted. The pigment particles are arranged in a curved manner, following either a convex curvature (also referred to in the art as a negative curve orientation) or a concave curvature (also referred to in the art as a positive curve orientation). Methods and magnets for producing said effect are disclosed in, for example, EP2 263 806 A1, EP 1674 282 B1, EP2 263 807 A1, W O2004/007095 A2, WO 2012/104098 A1, and WO 2014/198905 A2.

An optical effect known as the Venetian-blind effect (Venetian-blind effect) can also be produced. The venetian blind effect includes pigment particles oriented in the following manner: they give visibility to the underlying substrate surface in the particular direction of observation, so that indicia or other features present on or in the substrate surface become apparent to the observer, while they block visibility in other directions of observation. Methods and magnets for producing said effect are disclosed in e.g. US 8,025,952 and EP 1819 525 B1.

An optical effect known as the moving-ring effect (moving-ring effect) can also be produced. The moving ring effect consists of an optical illusive image of an object, such as a funnel, cone, bowl, circle, ellipse, and hemisphere, that appears to move in any x-y direction depending on the angle of inclination of the optical effect layer. Methods and magnets for producing said effect are disclosed in e.g. EP1 710 756 A1, US 8,343,615, EP2 306 A1, EP2 325 677 A2, WO 2011/092502 A2, US 2013/084411, WO2014 108404 A2 and WO2014/108303 A1.

An optical effect may also be produced that provides an optical impression of a pattern of bright and dark areas that move when the optical effect is tilted. Methods and magnets for producing said effect are disclosed in, for example, WO 2013/167425 A1.

An optical effect may also be produced that provides an optical impression of an annular body having a size that changes upon tilting the optical effect. Methods and magnets for producing these optical effects are disclosed in, for example, WO 2017/064052 A1, WO 2017/080698 A1 and WO 2017/148789 A1.

It is also possible to produce an optical effect that provides an optical impression of more than one ring-shaped body 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 is also possible to produce optical effects that provide an optical impression of a crescent that moves and rotates when tilted. Methods and magnets for producing said effect are disclosed in, for example, WO 2019/215148 A1.

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

An optical effect can be produced which provides an optical impression of an orthogonal parallax optical effect, i.e. in the form of in this case brightly reflective vertical bars which move in the longitudinal direction when the substrate is tilted about the transverse/latitudinal axis or in the horizontal/latitudinal direction when the substrate is tilted about the longitudinal axis. Methods and magnets for producing said effect are disclosed in, for example, co-pending PCT patent application PCT/EP 2020/052265.

An optical effect may be generated that provides an optical impression of one ring-shaped body surrounded by more than one ring-shaped body, wherein the shape and/or brightness of the more than one ring-shaped body changes upon tilting. Methods and magnets for producing said effect are disclosed in, for example, co-pending PCT patent application PCT/EP 2020/054042.

An optical effect may be produced that provides an optical impression of a plurality of dark spots and a plurality of bright spots that not only move and/or appear and/or disappear diagonally when the substrate is tilted with respect 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 said effect are disclosed in, for example, co-pending EP patent applications EP19205715.6 and EP 19205716.4.

The magnetic field generating means described herein may be at least partially embedded in a non-magnetic support matrix made of one or more non-magnetic materials.

The non-magnetic support plate (x 40) described herein and the non-magnetic material of the non-magnetic support matrix described herein are preferably independentlySelected from the group consisting of non-magnetic metals and engineering plastics and polymers. Non-magnetic metals include, without limitation, aluminum alloys, brass (alloys of copper and zinc), titanium alloys, and austenitic steels (i.e., non-magnetic steels). Engineering plastics and polymers include, without limitation, polyaryletherketone (PAEK) and its derivatives, polyetheretherketone (PEEK), polyetherketoneketone (PEKK), polyetheretherketoneketone (PEEKK), and Polyetherketoneetherketoneketone (PEKEKK); polyacetals, polyamides, polyesters, polyethers, copolyether esters, polyimides, polyetherimides, high Density Polyethylene (HDPE), ultra High Molecular Weight Polyethylene (UHMWPE), polybutylene terephthalate (PBT), polypropylene, acrylonitrile Butadiene Styrene (ABS) copolymers, fluorinated and perfluorinated polyethylenes, polystyrene, polycarbonate, polyphenylene sulfide (PPS) and liquid crystal polymers. Preferred materials are PEEK (polyetheretherketone), POM (polyoxymethylene), PTFE (polytetrafluoroethylene),(polyamides) and PPS.

The magnetic field generating means described herein may comprise a magnetic plate carrying one or more embossments, engravings or cuts (cut-out). WO 2005/002866A1 and WO 2008/046702 A1 are examples for such engraved magnetic plates.

Suitable magnetic field generating means for biaxially orienting the flake-like magnetic or magnetizable pigment particles described herein are not limited.

A particularly preferred apparatus for biaxially orienting pigment particles is disclosed in EP2 157 A1. While the substrate carrying the coating comprising pigment particles is in motion, the device disclosed in EP2 157 A1 provides a dynamic magnetic field that changes its direction to force the pigment particles to vibrate rapidly until the two major axes, the X-axis and the Y-axis, become substantially parallel to the substrate surface, i.e. the pigment particles rotate until they reach a stable platelet-like configuration with the X-axis and the Y-axis substantially parallel to the substrate surface and planarized in said two dimensions.

Other particularly preferred means for biaxially orienting pigment particles include Halbach arrays of linear permanent magnets, i.e. devices comprising a plurality of magnets having different magnetization directions and cylindrical devices. A detailed description of Halbach permanent magnets is given by z.q.zhu and d.howe (Halbach permanent magnets and applications: a review, iee.proc.electric Power application, 2001, 148, pages 299-308). The magnetic field generated by such halbach arrays has the following properties: which is concentrated on one side while it is almost attenuated to zero on the other side. Linear Halbach (Halbach) arrays are disclosed in, for example, WO 2015/086257 A1 and WO 2018/019594 A1, and Halbach cylinder devices are disclosed in EP 3 224 055 B1.

Other particularly preferred means for biaxially orienting the pigment particles are rotating magnets (spinning magnets) comprising disk-shaped rotating magnets or magnetic field generating means magnetized predominantly along their diameter. Suitable rotating magnets or magnetic field generating means which generate a radially symmetrical (radial symmetric) time-variable magnetic field such that the magnetic or magnetizable pigment particles of the as yet uncured coating composition are biaxially oriented are described in US 2007/0172261 A1. These magnets or magnetic field generating devices are driven by a shaft (or spindle) connected to an external motor. CN 102529326B discloses an example of an apparatus comprising a rotating magnet which may be adapted for biaxial orientation of magnetic or magnetizable pigment particles. In a preferred embodiment, a suitable means for biaxially orienting the magnetic or magnetizable pigment particles is a shaftless disk-like rotating magnet or magnetic field generating means actuated (constrained) in a housing made of a non-magnetic, preferably non-conductive material and driven by one or more magnetic coils (magnet-wire coil) wound around the housing. Examples of such shaftless disk-shaped rotating magnets or magnetic field generating devices are disclosed in WO 2015/082344 A1, WO 2016/026896 A1, and WO2018/141547 A1.

Other particularly preferred means for biaxially orienting pigment particles are shown in fig. 3 and comprise a) at least a first group (S1) and a second group (S2), the first and second groups (S1, S2) each comprising one first rod-like dipole magnet and two second rod-like dipole magnets, the magnetic axis of the first rod-like dipole magnet being oriented substantially parallel to the substrate during magnetic orientation and the magnetic axis of the second rod-like dipole magnet being oriented substantially perpendicular to the substrate; and b) a pair (P1) of third rod-like dipole magnets having their magnetic axes oriented substantially parallel to the substrate, such as those disclosed in co-pending European patent application EP 20176506.2.

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

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 is at least in its cured or solid state (also referred to herein as the second state) at least partially transparent to a wavelength range comprised between 200nm and 3500nm, 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. Thus, the particles contained in the binder material in its cured or solid state and their orientation-dependent reflectivity (orientation-dependent reflectivity) may 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 comprised between 200nm and 800nm, more preferably comprised between 400nm and 700 nm. Here, the term "transparent" means that the transmission of electromagnetic radiation through a 20 μm layer of cured binder material (excluding the plate-like magnetic or magnetizable pigment particles, but including all other optional components of the OEL in the presence of such components) present in the OEL is at least 50%, more preferably at least 60%, even more preferably at least 70%, at the wavelength of interest. This can be determined, for example, by measuring the transmittance of test pieces of cured binder material (excluding non-spherical magnetic or magnetizable pigment particles) in accordance with well-established test methods, such as DIN 5036-3 (1979-11). If OEL is used as a covert security feature, typical technical means would be necessary to detect the (complete) optical effect produced by OEL under various lighting conditions including selected non-visible wavelengths; the detection requires that the wavelength of the incident radiation is selected to be outside the visible range, for example in the near UV range.

Suitable examples of non-spherical, preferably platelet-shaped, magnetic or magnetizable pigment particles described herein include, without limitation, pigment particles comprising: a magnetic metal selected from the group consisting of cobalt (Co), iron (Fe), and nickel (Ni); magnetic alloys of iron, manganese, cobalt, nickel or mixtures of two or more thereof; magnetic oxides of chromium, manganese, cobalt, iron, nickel, or a mixture of two or more thereof; or a mixture of two or more thereof. The term "magnetic" in relation to metals, alloys and oxides refers to ferromagnetic (ferrimagnetic) or ferrimagnetic (ferrimagnetic) metals, alloys and oxides. The magnetic oxides of chromium, manganese, cobalt, iron, nickel or mixtures of two or more thereof may be pure (pure) or mixed (mixed) oxides. Examples of magnetic oxides include, without limitation, hematite (Fe), for example ₂ O ₃ ) Magnetite (Fe) ₃ O ₄ ) Iso-iron oxide, chromium dioxide (CrO) ₂ ) Magnetic ferrites (MFe) ₂ O ₄ ) Magnetic spinel (MR) ₂ O ₄ ) Magnetic hexaferrite (MFe) ₁₂ O ₁₉ ) Magnetic orthoferrite (RFeO) ₃ ) Magnetic garnet M ₃ R ₂ (AO ₄ ) ₃ Wherein M represents a divalent metal, R represents a trivalent metal, and a represents a tetravalent metal.

Examples of non-spherical, preferably plate-like magnetic or magnetizable pigment particles described herein include, without limitation, 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 one or more further layers are: layer A, independent thereofThe ground is made of the following components: selected from, for example, magnesium fluoride (MgF) ₂ ) Isometal fluoride, silicon oxide (SiO), silicon dioxide (SiO) ₂ ) Titanium oxide (TiO) ₂ ) And alumina (Al) ₂ O ₃ ) More preferably silicon dioxide (SiO) ₂ ) (ii) a Or layer B, independently made of: selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, and more preferably one or more selected from the group consisting of aluminum (Al), chromium (Cr), and nickel (Ni), and still more preferably aluminum (Al); or a combination of one or more layers a such as those described above and one or more layers B such as those described above. Typical examples of the flake-like magnetic or magnetizable pigment particles which are the above-described multilayer structure include, without limitation, an A/M multilayer structure, an A/M/A multilayer structure, an A/M/B multilayer structure, an A/B/M/A multilayer structure, an A/B/M/B/A multilayer structure, a B/M/B multilayer structure, a B/A/M/A multilayer structure, a B/A/M/B multilayer structure, and a B/A/M/B/A multilayer structure, wherein the layer A, the magnetic layer M, and the layer B are selected from those described above.

The radiation-curable coating compositions described herein may comprise non-spherical, preferably plate-like, optically variable magnetic or magnetizable pigment particles, and/or non-spherical, preferably plate-like, magnetic or magnetizable pigment particles which do not have optically variable properties. Preferably, at least a part of the magnetic or magnetizable pigment particles described herein consist of non-spherical, preferably platelet-shaped, optically variable magnetic or magnetizable pigment particles. In addition to the overt security feature provided by the color change properties of the optically variable magnetic or magnetizable pigment particles, which allows an article or security document bearing an ink, coating composition, or coating comprising the optically variable magnetic or magnetizable pigment particles described herein to be easily detected, confirmed and/or identified using an independent human sense to prevent their possible counterfeiting, the optical properties of the optically variable magnetic or magnetizable pigment particles may also be used as a machine readable tool for confirming OEL. Thus, the optical properties of the optically variable magnetic or magnetizable pigment particles can simultaneously be used as a covert or semi-covert security feature in an authentication process in which the optical (e.g. spectroscopic) properties of the pigment particles are analyzed, thereby improving the security.

The use of non-spherical, preferably flake-like, optically variable magnetic or magnetizable pigment particles in coatings for the production of OEL improves the significance of OEL as a security feature in security document applications, since such materials are reserved for the security document printing industry and are not commercially available to the public.

As mentioned above, preferably at least a part of the non-spherical, preferably plate-like, magnetic or magnetizable pigment particles consists of non-spherical, preferably plate-like, optically variable magnetic or magnetizable pigment particles. These are more preferably selected from the group consisting of magnetic thin film interference pigment particles, magnetic cholesteric liquid crystal pigment particles, interference coated pigment particles comprising 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; EP2 402 401 B1; WO 2019/103937 A1; WO 2020/006286A1 and the documents cited therein. Preferably, the magnetic thin-film interference pigment particles comprise pigment particles having a five-layer Fabry-Perot (Fabry-Perot) multilayer structure and/or pigment particles having a six-layer Fabry-Perot multilayer structure and/or pigment particles having a seven-layer Fabry-Perot multilayer structure and/or pigment particles having a multilayer structure incorporating more than one layer of a multilayer Fabry-Perot structure.

Preferred five-layer fabry-perot multilayer structures comprise absorber (absorber)/dielectric (dielectric)/reflector (reflector)/dielectric/absorber multilayer structures, wherein the reflector and/or the absorber are also magnetic layers, preferably the reflector and/or the absorber are magnetic layers comprising 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).

A preferred six-layer fabry-perot multilayer structure comprises an absorber/dielectric/reflector/magnetic (magnetic)/dielectric/absorber multilayer structure.

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

Preferably, the reflector layers described herein are independently made of: selected from the group consisting of metals and metal alloys, preferably selected from the group consisting of reflective metals and reflective metal alloys, more preferably selected from the group consisting of aluminum (Al), silver (Ag), copper (Cu), gold (Au), platinum (Pt), tin (Sn), titanium (Ti), palladium (Pd), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni), and alloys thereof, even more preferably one or more selected from the group consisting of aluminum (Al), chromium (Cr), nickel (Ni), and alloys thereof, and still more preferably aluminum (Al). Preferably, the dielectric layers are independently made of: selected from e.g. magnesium fluoride (MgF) ₂ ) Aluminum fluoride (AlF) ₃ ) Cerium fluoride (CeF) ₃ ) Lanthanum fluoride (LaF) ₃ ) Sodium aluminum fluoride (e.g., na) ₃ AlF ₆ ) Neodymium fluoride (NdF) ₃ ) Samarium fluoride (SmF) ₃ ) Barium fluoride (BaF) ₂ ) Calcium fluoride (CaF) ₂ ) Metal fluorides such as lithium fluoride (LiF) and the like, and silicon oxides (SiO), silicon dioxides (SiO) ₂ ) Titanium oxide (TiO) ₂ ) Alumina (Al) ₂ O ₃ ) And the like, more preferably selected from the group consisting of magnesium fluoride (MgF) ₂ ) And silicon dioxide (SiO) ₂ ) More than one of the group consisting of magnesium fluoride (MgF), and still more preferably magnesium fluoride (MgF) ₂ ). Preferably, the absorber layer is independently made of: selected from aluminum (Al), silver (Ag), copper (Cu), palladium (Pd), platinum (Pt), titanium (T)i) Vanadium (V), iron (Fe), tin (Sn), tungsten (W), molybdenum (Mo), rhodium (Rh), niobium (Nb), chromium (Cr), nickel (Ni), a metal oxide thereof, a metal sulfide thereof, a metal carbide thereof, and a metal alloy thereof, more preferably selected from the group consisting of chromium (Cr), nickel (Ni), a metal oxide thereof, and a metal alloy thereof, and still more preferably one or more selected from the group consisting of chromium (Cr), nickel (Ni), and a metal alloy thereof. 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). While 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 material consisting of Cr/MgF ₂ /Al/Ni/Al/MgF ₂ A seven-layer Fabry-Perot absorber/dielectric/reflector/magnetic body/reflector/dielectric/absorber multilayer structure consisting of/Cr multilayer structures.

The magnetic thin film interference pigment particles described herein may be multilayer pigment particles that are considered safe for human health and the environment and are based on, for example, five-layer fabry-perot multilayer structures, six-layer fabry-perot multilayer structures, and seven-layer fabry-perot multilayer structures, wherein the pigment particles comprise one or more magnetic layers comprising a magnetic alloy having a substantially nickel-free composition (composition) comprising about 40wt-% to about 90wt-% iron, about 10wt-% to about 50wt-% chromium, and about 0wt-% to about 30wt-% aluminum. Typical examples of multilayer pigment particles considered to be safe for human health and the environment can be found in EP2 402 B1, the content of which is incorporated herein by reference in its entirety.

Suitable magnetic cholesteric liquid crystal pigment particles that exhibit optically variable properties include, without limitation, magnetic single layer cholesteric liquid crystal pigment particles and magnetic multilayer cholesteric liquid crystal pigment particles. Such pigment particles are disclosed, for example, in WO 2006/063926 A1, U.S. Pat. No. 6,582,781 and U.S. Pat. No. 6,531,221. WO 2006/063926 A1 discloses monolayers with further specific properties such as magnetizability with high brightness and discoloration properties and pigment particles obtained therefrom. Disclosed are monolayers and compositions prepared by comminutingCommittee) the monolayer and the pigment particles obtained therefrom comprise a three-dimensionally crosslinked cholesteric liquid crystal mixture and magnetic nanoparticles. U.S. Pat. No. 6,582,781 and U.S. Pat. No. 6,410,130 disclose platelet-shaped cholesteric multilayer pigment particles comprising sequences A ¹ /B/A ² Wherein A is ¹ And A ² May be the same or different and each comprises at least one cholesteric layer, and B is an intermediate layer absorbing the cholesteric layer or layers ¹ And A ² All or a portion of the transmitted light and imparts magnetism to the intermediate layer. US 6,531,221 discloses plate-like cholesteric multilayer pigment particles comprising the sequence a/B and optionally C, wherein a and C are absorbing layers comprising magnetic properties-imparting pigment particles, and B is a cholesteric layer.

Suitable interference coating pigments comprising more than one magnetic material include, without limitation: a structure comprising a substrate selected from the group consisting of a core coated with one or more layers, wherein at least one of the core or the one or more layers has magnetic properties. For example, suitable interference coating pigments include: cores made of magnetic materials, such as those described above, coated with one or more layers made of one or more metal oxides, or they have a composition comprising synthetic or natural mica, layered silicates (e.g. talc, kaolin and sericite), glass (e.g. borosilicate), silica (SiO), or mixtures thereof ₂ ) Aluminum oxide (Al) ₂ O ₃ ) Titanium oxide (TiO) ₂ ) Graphite and mixtures of two or more thereof. Furthermore, more than one additional layer, for example a coloured layer, may be present.

The non-spherical, preferably plate-like, magnetic or magnetizable pigment particles described herein preferably have a size d50 of between about 2 μm and about 50 μm (measured according to direct optical granulometry).

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

As described herein, the method described herein comprises step d): the coating (x 10) is at least partially cured to a second state, thereby fixing the magnetic or magnetizable pigment particles in the position and orientation they adopt. The first liquid state of the radiation-curable coating composition 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 are provided by using a specific type of radiation-curable coating composition. For example, the components of the radiation curable coating composition other than the non-spherical magnetic or magnetizable pigment particles may take the form of inks or radiation curable coating compositions, such as those used in security applications such as banknote printing. The aforementioned first and second states are provided by using a material that shows an increase in viscosity in a reaction of exposure to electromagnetic radiation. That is, when the fluid binder material is cured or solidified, the binder material transitions to a second state in which the non-spherical magnetic or magnetizable pigment particles are fixed in their current position and orientation and are no longer able to move or rotate within the binder material. As used herein, by "at least partially curing the coating (x 10)" it is meant that the non-spherical, preferably plate-like, magnetic or magnetizable pigment particles are fixed/frozen in the position and orientation they adopt 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 for producing the coating (x 10) described herein comprises non-spherical, preferably platelet-shaped, magnetic or magnetizable pigment particles described herein. Radiation curing, in particular 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 any loss of information after the magnetic orientation step. Preferably, step d) is carried out by irradiation with UV-visible light (i.e. UV-visible radiation curing) or by electron beam (electron beam radiation curing), more preferably by irradiation with UV-visible light: simultaneously with or after step c), at least partially curing the coating (x 10) and the one or more markings (x 30) with a curing unit (x 50) as described herein. According to a preferred embodiment, the radiation curable coating composition comprising the non-spherical, preferably platelet-shaped, magnetic or magnetizable pigment particles described herein is a UV-Vis curable coating composition.

Preferably, the UV-Vis curable coating composition comprising non-spherical, preferably platelet-shaped magnetic or magnetizable pigment particles as described herein is a free radical curable composition; a cationically curable composition; or a radically and cationically (known in the art as hybrid) curable composition. In other words, the UV-Vis curable coating composition preferably comprises monomers and/or oligomers selected from the group consisting of radically curable compounds, cationically curable compounds, and mixtures of radically and cationically curable compounds.

Cationically curable compositions include one or more cationic compounds which cure by a cationic mechanism, which typically involves activation by irradiation of one or more photoinitiators which release a cationic species, such as an acid, followed by initiation of cure to react and/or crosslink the monomers and/or oligomers, thereby hardening the coating composition. Preferably, the one or more cationically curable compounds are selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, oxetanes, and tetrahydrofurans, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl containing compounds, and mixtures thereof, preferably the cationically curable compounds are selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, oxetanes, and tetrahydrofurans, lactones, and mixtures thereof.

Free radical curable compositions include one or more free radical compounds that cure by a free radical mechanism that typically includes activation by irradiation of one or more photoinitiators, thereby generating free radicals, followed by initiation of polymerization to harden the coating composition. Preferably, the radically curable compound is selected from acrylates, preferably from the group consisting of 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 both acrylates and the corresponding methacrylates.

Hybrid curable compositions include one or more cationic compounds and one or more free radical compounds that cure by two mechanisms described herein.

Depending on the compounds used for preparing the UV-Vis curable coating composition comprising the non-spherical, preferably platelet-shaped magnetic or magnetizable pigment particles described herein, different photoinitiators may be used. Suitable examples of free radical photoinitiators are known to those skilled in the art and include, without limitation, acetophenones, benzophenones, benzyldimethyl ketals, α -aminoketones, α -hydroxyketones, 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, without limitation, onium salts such as organoiodonium 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 useful photoinitiators can be found in standard textbooks. It may also be advantageous to include a sensitizer along with more than one photoinitiator to achieve effective curing. Typical examples of suitable photosensitizers include, without limitation, isopropyl-thioxanthone (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. The one or more photoinitiators included in the UV-Vis curable coating composition are preferably present in a total amount of about 0.1wt-% to about 20wt-%, more preferably about 1wt-% to about 15wt-%, based on the total weight of the UV-Vis curable coating composition.

The radiation curable coating composition comprising non-spherical, preferably platelet-shaped magnetic or magnetizable pigment particles 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 include, without limitation, 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), homogeneity (e.g., anti-settling agents, fillers, and plasticizers), foamability (e.g., defoamers), lubricity (waxes, oils), UV stability (light stabilizers), adhesion, antistatic properties, storage stability (polymerization inhibitors), and the like. The additives described herein may be present in the coating composition in amounts and forms known in the art, including so-called nanomaterials wherein at least one of the sizes of the additives is in the range of 1 to 1000 nm.

The radiation curable coating composition comprising non-spherical, preferably plate-like, magnetic or magnetizable pigment particles described herein may further comprise one or more marker substances or tracers (taggants) and/or one or more machine readable materials selected from the group consisting of magnetic materials (other than the magnetic or magnetizable pigment particles described herein), luminescent materials, electroluminescent materials, upconversion materials, conductive materials and infrared absorbing materials. As used herein, the term "machine-readable material" refers to a material that exhibits at least one unique property that is detectable by a device or machine and that can be included in a coated film to provide a method for authenticating the coated film or an article comprising the coated film by using a particular detection and/or authentication instrument.

The radiation curable coating composition described herein may be prepared by: the magnetic or magnetizable pigment particles described herein and one or more additives, when present, are dispersed or mixed in the presence of the binder material described herein (particularly the UV-Vis curable coating composition preferably comprises monomers and/or oligomers selected from the group consisting of radically curable compounds, cationically curable compounds, and mixtures of radically and cationically 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 ingredients, or may be added at a later stage, i.e. after the formation of the liquid coating composition.

The method described herein further comprises, after step b) described herein, step c): applying a topcoat composition as described herein over the coating (x 10) as described herein. The topcoat composition described herein is applied in the form of one or more indicia (x 30) described herein and partially overlaps (i.e., overlaps in at least one region) with the coating (x 10) described herein, wherein the radiation curable coating composition of the coating (x 10) is still in a wet and unpolymerized state and the magnetic or magnetizable pigment particles are free to move and rotate.

Preferably, the time between step b) as described herein and step c) as described herein is less than about 60 seconds, more preferably less than 5 seconds, and still more preferably less than about 2 seconds. In other words, a step of applying the topcoat composition over the coating (x 10) and in the form of one or more markings (x 30) is carried out after step b), wherein the substrate (x 20) bearing the coating (x 10) has been removed from the magnetic field of the magnetic field generating device.

As used herein, the term "indicia" shall mean continuous and discontinuous layers consisting of distinguishing marks or logos or patterns. Preferably, the one or more indicia (x 30) recited herein are selected from the group consisting of codes, symbols, alphanumeric symbols, graphics, geometric patterns (e.g., circles, triangles, and regular or irregular polygons), letters, words, numbers, logos, pictures, portraits, and combinations thereof. Examples of the code include coded marks such as coded alphanumeric data, one-dimensional bar codes, two-dimensional codes (QR-codes), data matrices (datamatrix), and IR read codes. The one or more markers (x 30) described herein may be solid markers and/or raster markers.

The topcoat compositions described herein are applied in the form of one or more indicia (x 30) described herein by an application method, preferably a non-contact fluid micro-dispensing method, preferably selected from the group consisting of spray coating, aerosol jet printing, electrohydrodynamic printing and ink jet printing, more preferably by an ink jet printing method, wherein the ink jet printing method is a variable information printing method that allows the unique production of one or more indicia (x 30) on or in an 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 may be advantageously used to produce Optical Effect Layers (OELs) exhibiting one or more of the indicia described herein, including variable halftones. Inkjet halftoning is a replication technique that simulates a continuous tone image comprising an infinite number of colors or shades of gray by applying a variable inkjet deposit or grammage.

Spraying is a technique that involves 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. Jet printing allows spots and lines to be printed. Suitable compositions for jet printing typically have a viscosity of about 10mPa.s to about 11Pa.s (25 ℃,1000 s) ^-1 ) In between. The resolution of the jet printing is in the millimeter range. In, for example, F.C. Krebs, solar Energy Materials&Jet printing is described in Solar Cells (2009), 93, page 407.

Aerosol Jet Printing (AJP) is an emerging non-contact direct write method aimed at producing fine features on a wide range of substrates. AJP is compatible with a wide range of materials and free-form deposition, allowing high resolution (on the order of about 10 microns) in combination with 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 nebulizer, to have a pressure of from typically about 1mPa.s to about 1Pa.s (25 ℃,1000 s) ^-1 ) Compositions of intermediate viscosity generate aerosols. Aerosol jet printing is described, for example, in N.J. Wilkinson et al, the International Journal of Advanced Manufacturing Technology (2019) 105.

Electrohydrodynamic ink jet printing is a high resolution ink jet printing technique. Electrohydrodynamic ink jet printing techniques utilize externally applied electric fields to controlThe size of the droplets, the frequency of ejection and the location on the substrate are made to achieve higher resolution than conventional inkjet printing while maintaining high production speeds. The resolution of electrohydrodynamic ink-jet printing is about two orders of magnitude higher than conventional ink-jet printing techniques; thus, it can be used to orient nano-and micro-scale patterns. Electrohydrodynamic ink-jet printing can be used for both DOD or continuous mode. The viscosity of the compositions for electrohydrodynamic ink jet printing is typically in the range of about 1mPa.s to about 1Pa.s (25 ℃,1000 s) ^-1 ) In between. Electrohydrodynamic ink jet printing techniques are described, for example, in p.v. raje and n.c. murmu, international Journal of emissive Technology and Advanced Engineering, (2014), 4 (5), pages 174-183.

Slit-die coating (slot-die coating) is a 1-dimensional coating technique. Slot-die extrusion coating allows coating strips of material, which is well suited for manufacturing multilayer coating films having different strips of material laminated on top of each other. Alignment of the pattern is produced by translation of the coating head in a direction perpendicular to the web feed (web) motion. The slit extrusion coating head includes a mask defining a slit of the coating head through which slit extrusion coating ink is dispersed. In F.C. Krebs, solar Energy Materials&One example of a slot-extrusion coating head is described in Solar Cells (2009), 93, pages 405-406. Suitable compositions for slot-die coating typically have a viscosity of about 1mPa.s to about 20mPa.s (25 ℃,1000 s) ^-1 ) In between.

According to one embodiment, the topcoat composition described herein is printed with one or more indicia (x 30) described herein by an inkjet printing process, preferably a Continuous Inkjet (CIJ) printing process or a drop-on-demand (DOD) inkjet printing process, more preferably a drop-on-demand (DOD) inkjet printing process. Drop-on-demand (DOD) printing is a non-contact printing method in which droplets are only produced when required for printing, and are typically produced by a jetting mechanism rather than by destabilizing the jet. DOD printing is divided into piezoelectric pulses, thermal jets and valve jets (viscosity between about 1mpa.s and about 1pa.s (25) depending on the mechanism used to generate the drops in the print head℃，1000s ^-1 ) Inter) and electrostatic methods.

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

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

The topcoat compositions described herein may further comprise one or more marking substances or tracers and/or one or more machine-readable substances such as those described for use in coatings (x 10) comprising the non-spherical magnetic or magnetizable pigment particles described herein, provided that the size of the substance, tracer, material is suitable for the application method described herein. As noted herein, the topcoat compositions described herein do not include magnetic or magnetizable pigment particles.

The process described herein further comprises step d): simultaneously with or after step c), at least partially curing the coating (x 10) and the one or more markings (x 30) with a curing unit (x 50) as described herein. By "partially simultaneously", it is meant that the two steps are performed partially simultaneously, i.e. the times at which the individual steps are performed partially overlap. In the context of the present description, when curing is performed partially simultaneously with the application step c), it must be understood that after forming the one or more marks, curing becomes effective before full or partial curing.

For embodiments of the methods described herein, wherein there is no intermediate step between step C) and step d), said step C) is applying a top-coat composition over the coating (x 10) described herein, and said step d) is at least partially curing the coating (x 10) and the one or more indicia (x 30) with the curing unit (x 50) described herein (see, e.g., fig. 2A, 2B, 2C, and 2E-1-2E3, the time between step C) and step d is preferably between about 0 to 5 minutes, more preferably between about 0 to 1 minute, still more preferably between about 0 to 10 seconds, and still more preferably between about 0 to 5 seconds.

The at least partially curing step described herein is a radiation at least partially curing step, and UV-Vis light radiation curing is more preferred, as these techniques advantageously result in a very fast curing process, and thus significantly reduce the manufacturing time of any article comprising the OEL described herein. In addition, radiation curing has the advantage of giving the coating composition an almost instantaneous increase in viscosity. It is particularly preferred that the radiation curing is carried out by photo-polymerization under the influence of actinic light (active light) in the UV or blue part of the electromagnetic spectrum (typically 200nm to 650nm; more preferably 200nm to 420 nm). Devices for UV-visible curing may include high power Light Emitting Diode (LED) lamps or arc discharge lamps, such as Medium Pressure Mercury Arc (MPMA) or metal vapor arc lamps, as the source of actinic radiation. Performing a step d) of at least partially curing the coating (x 10) and the one or more marks (x 30) with the curing unit (x 50). Suitable curing units include devices for UV-visible light curing including high power Light Emitting Diode (LED) lamps or arc discharge lamps, such as Medium Pressure Mercury Arc (MPMA) or metal vapor arc lamps, as the source of actinic radiation.

Several embodiments of steps b) and y) of exposing the coating (x 10) to the magnetic field of a magnetic field generating device are described herein, as shown in fig. 2A-E.

According to one embodiment shown in fig. 2A, the method described herein comprises:

step b): exposing the coating (x 10) to a magnetic field of a magnetic field generating device (B1) thereby uniaxially orienting at least a portion of the magnetic or magnetizable pigment particles;

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to one embodiment shown in fig. 2B, the method described herein comprises:

step b): exposing the coating (X10) to a magnetic field of a magnetic field generating means (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles, wherein the magnetic or magnetizable pigment particles are platelet-shaped magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining a plane of major extension of the particles, preferably said step is performed thereby biaxially orienting at least a portion of the platelet-shaped magnetic or magnetizable pigment particles such that both their X-axis and Y-axis are substantially parallel to the substrate surface;

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to one embodiment, the method described herein comprises:

step B) comprises the two steps described herein, a first step B1) and a further step B2), said first step B1) comprising exposing the coating (X10) to a magnetic field of a magnetic field generating means (B1) thereby biaxially orienting at least a part of the magnetic or magnetizable pigment particles, wherein the magnetic or magnetizable pigment particles are platelet-shaped magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the main plane of extension of the particles, said further step B2) comprising exposing the coating (X10) to a magnetic field of a second magnetic field generating means (B2) thereby uniaxially reorienting at least a part of the platelet-shaped magnetic or magnetizable particles, wherein said step B2) is performed partially simultaneously, simultaneously with, or after step B1) (see fig. 2C, wherein step B2) is performed after step B1);

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to another embodiment shown in fig. 2D-1, the method described herein comprises:

step b): exposing the coating (x 10) to a magnetic field of a magnetic field generating device (B1) thereby uniaxially orienting at least a portion of the magnetic or magnetizable pigment particles;

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein;

simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first regions of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means (B2) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10); and

simultaneously with part of step y) or after step y), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

Wherein said step y) is performed partially simultaneously with step d) or before step d).

According to another embodiment shown in fig. 2D-2, the method described herein comprises:

carrying out step b): exposing the coating (x 10) to a magnetic field of a magnetic field generating means (B1) thereby biaxially orienting at least a part of the magnetic or magnetizable pigment particles;

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein;

simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first regions of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means (B2) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10); and

simultaneously with part of step y) or after step y), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to another embodiment, the method described herein comprises:

step B) comprises the two steps described herein, a first step B1) and a further step B2), said first step B1) comprising exposing the coating (x 10) to the magnetic field of the magnetic field generating means (B1) thereby biaxially orienting at least a part of the magnetic or magnetizable pigment particles, said further step B2) comprising exposing the coating (x 10) to the magnetic field of the second magnetic field generating means (B2) thereby uniaxially reorienting at least a part of the plate-like magnetic or magnetizable particles, wherein said further step B2) is performed simultaneously, simultaneously with part of step B1), or after step B1) (see fig. 2D-3, wherein step B2) is performed after step B1);

after step b), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein;

simultaneously with part of step c) or after step c), step x): selectively at least partially curing one or more first regions of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a third magnetic field generating means (B3) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10); and

simultaneously with part of step y) or after step y), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to another embodiment shown in fig. 2E-1, the method described herein comprises:

carrying out step b): exposing the coating (x 10) to a magnetic field of a magnetic field generating means (B1) thereby uniaxially orienting at least a part of the magnetic or magnetizable pigment particles;

simultaneously with part of step b) or after step b), step x): selectively at least partially curing one or more first regions of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means (B2) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10);

after step y), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to another embodiment shown in fig. 2E-2, the method described herein comprises:

step b): exposing the coating (x 10) to a magnetic field of a magnetic field generating device (B1) thereby biaxially orienting at least a portion of the magnetic or magnetizable pigment particles;

simultaneously with part of step b) or after step b), step x): selectively at least partially curing one or more first regions of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means (B2) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10);

after step y), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

According to another embodiment, the method described herein comprises:

step B) comprises the two steps described herein, a first step B1) and a further step B2), said first step B1) comprising exposing the coating (x 10) to a magnetic field of a magnetic field generating means (B1) thereby biaxially orienting at least a part of the magnetic or magnetizable pigment particles, said further step B2) comprising exposing the coating (x 10) to a magnetic field of a second magnetic field generating means (B2) thereby uniaxially orienting at least a part of the platy magnetic or magnetizable particles, wherein said further step B2) is performed partially simultaneously, simultaneously with step B1), or after step B1) (see fig. 2E-3, wherein step B2) is performed after step B1);

after step b) or partially simultaneously with step b), step x): selectively at least partially curing one or more first regions of the coating layer (x 10) of the radiation curable coating composition of step b) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating layer (x 10) remain unexposed to the irradiation, said selectively at least partially curing step being performed by a selective curing unit (x 60) as described herein;

after step x), step y): exposing the coating (x 10) to the magnetic field of a third magnetic field generating means (B3) so as to uniaxially orient at least a portion of the magnetic or magnetizable pigment particles of one or more second regions of the coating (x 10);

after step y), step c): applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30) described herein; and

simultaneously with part of step c) or after step c), step d): the coating (x 10) and the one or more markings (x 30) are at least partially cured with a curing unit (x 50) as described herein.

For embodiments of step x) described herein comprising selectively at least partially curing one or more first regions of the coating layer (x 10) of the radiation curable coating composition of step b) or step c) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second regions of the coating layer (x 10) remain unexposed to the herein described irradiation, a selective curing unit (x 60) is used. Selective curing allows the production of Optical Effect Layers (OELs) exhibiting patterns made of different areas, wherein the different areas have different patterns of magnetic orientation. The selective curing unit (x 60) may comprise the curing unit (x 50) described herein and one or more fixed or removable photomasks comprising one or more voids (voids) corresponding to a pattern to be formed as part of the coating. Alternatively, the selective curing unit (x 60) may be addressable, such as a scanned laser beam as disclosed in EP2 468 423 A1, an array of Light Emitting Diodes (LEDs) as disclosed in WO 2017/021504 A1, or an actinic radiation LED source (x 41) comprising an array of individually addressable actinic radiation emitters as disclosed in co-pending japanese laid-open application PCT/EP 2019/087072.

The present invention provides a method as described herein for producing an Optical Effect Layer (OEL) exhibiting one or more marks (x 30) on a substrate (x 20) as described herein, as well as a substrate (x 20) comprising one or more Optical Effect Layers (OEL) obtained thereby. The substrate (x 20) described herein is preferably selected from the group consisting of: paper or other fibrous materials such as cellulose (including woven and non-woven fibrous materials), paper-containing materials, glass, metal, ceramic, plastic and polymer, metallized plastic or polymer, composite materials, and mixtures or combinations of two or more thereof. Typical paper, paper-like (paper-like) or other fibrous materials are made from a variety of fibers including, without limitation, abaca, cotton, flax, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton/linen blends are preferred for banknotes, while wood pulp is typically used for non-banknote security documents. According to another embodiment, the substrate (x 20) described herein is based on plastics and polymers, metalized plastics or polymers, composites, and mixtures or combinations of two or more thereof. Suitable examples of plastics and polymers include: polyolefins such as Polyethylene (PE) and polypropylene (PP) including biaxially oriented polypropylene (BOPP), polyamides such as poly (ethylene terephthalate) (PET), poly (1, 4-butylene terephthalate) (PBT), poly (ethylene 2, 6-naphthalate) (PEN) and polyvinyl chloride (PVC). Spunbond (spunbond) olefin fibers such as are used in the trademarksThose sold under the market may also be used as substrates. Typical examples of metallized plastics or polymers include the plastics or polymer materials described above with metal deposited continuously or discontinuously on their surface. Typical examples of the metal include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), alloys thereof, and combinations of two or more of the foregoing metals. The metallization of the above-mentioned plastic or polymer materials can be done by an electrodeposition method, a high vacuum coating method or by a sputtering method. Typical example package of composite materialsIncluding but not limited to: a multilayer structure or laminate of paper and at least one plastic or polymeric material such as those described above and plastic and/or polymeric fibers incorporated into a paper-like or fibrous material such as those 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 wetting agents, and the like. When OELs produced according to the present invention exhibiting more than one marking (x 30) are used for decorative or cosmetic purposes including, for example, nail varnishes (finger nail varnishes), the OELs may be produced on other kinds of substrates including nails, artificial nails or other parts of animals or humans.

Also described herein is 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 one or more optical effect layers described herein, in particular such as those obtained by the method described herein, such that it is constituted by the security document or decorative element or object.

OELs produced according to the present invention should be on security documents or articles and in order to further enhance the level of security and to resist counterfeiting and illegal reproduction of said security documents or articles, the substrate may comprise printed, coated or laser marked or laser perforated markings, watermarks, security threads, fibers, plates (platters), luminescent compounds, windows, foils, labels and combinations of two or more thereof. Also to further enhance the level of security and resistance to counterfeiting and illegal reproduction of security documents and articles, the substrate may include one or more marking substances or taggants and/or machine readable substances (e.g., luminescent substances, UV/visible/IR absorbing substances, magnetic substances, and combinations thereof).

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

In order to increase the durability by stain or chemical resistance and cleanliness (clearness) and thereby increase the cycle life of security documents, articles or decorative elements or objects comprising OELs obtained by the methods described herein, or to modify their aesthetic appearance (e.g. optical gloss), more than one protective layer may be applied over the OEL. When present, more than one protective layer is typically made of a protective varnish. The protective varnish may be a radiation curable composition, a thermally drying composition, or any combination thereof. Preferably, one or more of the protective layers is a radiation curable composition, more preferably a UV-Vis curable composition. The protective layer is typically applied after the OEL is formed.

The invention further provides Optical Effect Layers (OELs) exhibiting one or more of the indicia (x 30) 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 (x 10) represents one or more marks, dots and/or lines, wherein the marks may have the same shape as one or more marks (x 30) made from the topcoat compositions described herein or may have a different shape.

OELs exhibiting more than one indicia (x 30) described herein can be disposed directly on a substrate on which it should be permanently retained (e.g., for banknote use). Optionally, for production purposes, the optical effect layer may also be provided on a temporary substrate, from which the OEL is subsequently removed. This may for example facilitate the production of Optical Effect Layers (OEL), especially when the binder material is still in its fluid state. Thereafter, after curing the coating composition to produce the OEL, the temporary substrate may be removed from the OEL.

Alternatively, in another embodiment, an adhesion layer may be present on the substrate exhibiting more than one indicium (x 30) or may be present on the substrate comprising the OEL, on the side of the substrate opposite to the side where the OEL is disposed or on the same side as the OEL and over the OEL. Thus, an adhesive layer may be applied to the OEL or to the substrate, the adhesive layer being applied after the curing step is completed. Such articles may be affixed to a wide variety of documents or other articles or items without printing or other methods including machinery and considerable effort. Alternatively, the substrate described herein comprising the OEL described herein may be in the form of a transfer foil, which may be applied to a document or article in a separate transfer step. For this purpose, the substrate is provided with a release coating on which OEL is produced as described herein. More than one adhesive layer may be applied over the produced optical effect layer.

Also described herein are substrates comprising more than one layer, i.e., two, three, four, etc., of Optical Effect Layers (OELs) obtained by the methods described herein.

Also described herein are articles, documents, in particular security documents, decorative elements and decorative objects, comprising the Optical Effect Layer (OEL) produced according to the present invention. Articles, in particular security documents, decorative elements or objects may comprise more than one layer (e.g. two layers, three layers, etc.) of OEL produced according to the present invention.

As mentioned above, OELs produced according to the present invention may be used for decorative purposes as well as for protecting and authenticating security documents.

Typical examples of decorative elements or objects include, without limitation, luxury goods, cosmetic packages, automotive parts, electronic/electrical appliances, furniture, and nail polish.

Security documents include, without limitation, documents of value and commercial goods of value. Typical examples of documents of value include, without limitation, banknotes, contracts, tickets, checks, vouchers, fiscal stamps and tax labels, agreements and the like, identity documents such as passports, identity cards, visas, driver's licenses, bank cards, credit cards, transaction cards (transactions cards), access documents (access documents) or cards, admission tickets, public transportation tickets, academic documents or academic degrees (titles) and the like, preferably banknotes, identity documents, authorization documents, driver's licenses, and credit cards. The term "value goods" means packaging materials, in particular for cosmetics, functional foods, pharmaceuticals, wines, tobacco products, beverages or foodstuffs, electrical/electronic products, textiles or jewelry, i.e. products which should be protected against counterfeiting and/or illegal reproduction in order to guarantee the contents of the packaging, for example genuine drugs. Examples of such packaging materials include, without limitation, labels such as authenticating brand labels, tamper-resistant labels, and seals. It is noted that the disclosed substrates, value documents and value commercial goods are given for illustrative purposes only and do not limit the scope of the invention.

Alternatively, the Optical Effect Layers (OEL) described herein may be produced onto a secondary substrate such as a security thread, security strip, foil, label, window or label, thereby being transferred to the security document in a separate step.

Those skilled in the art will envision several modifications to the specific embodiments described above without departing from the spirit of the invention. Such modifications are encompassed by the present invention.

Further, all documents mentioned throughout this specification are hereby incorporated herein by reference in their entirety as previously described.

Examples

The invention will now be discussed in more detail with reference to non-limiting examples. The following examples provide more details of producing an Optical Effect Layer (OEL) exhibiting more than one indicia. Four series of combinations of UV-Vis curable screen printing compositions and top-coat inkjet printing compositions have been prepared and are described in tables 1-3.

Table 1A: a combination of a free radical UV-Vis curable screen printing composition comprising plate-like magnetic or magnetizable pigment particles and a top-coat inkjet printing composition (E1, E3-E6 and C1-C5).

Table 1B: a combination of a free radical UV-Vis curable screen printing composition comprising plate-like magnetic or magnetizable pigment particles and a top-coat inkjet printing composition (E2).

Table 1C: a combination of a free radical UV-Vis curable screen printing composition comprising plate-like magnetic or magnetizable pigment particles and a top-coat inkjet printing composition (C11).

Table 2: a combination of cationic UV-Vis curable screen-printing compositions and top-coat inkjet printing compositions comprising plate-like magnetic or magnetizable pigment particles (E7-E11, E17, E19-E21 and C6-C10).

Table 3: a combination of a hybrid UV-Vis curable screen-printing composition comprising plate-like magnetic or magnetizable pigment particles and a top-coat inkjet printing composition (E12-E16 and E18).

TABLE 1A

(x) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles having a diameter d ₅₀ A flake (flake) shape of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, santa Rosa, calif.

TABLE 1B

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

TABLE 1C

7 layers of optically variable magnetic pigment particles of gold to green flakes having a diameter d ₅₀ A flake shape of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, santa Rosa, CA.

TABLE 2

(x) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles having a diameter d ₅₀ A flake shape of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, santa Rosa, calif.

TABLE 3

(x) 7 layers of gold to green flake-shaped optically variable magnetic pigment particles having a diameter d ₅₀ A flake shape of about 10.7 μm and a thickness of about 1 μm, obtained from VIAVI Solutions, santa Rosa, calif.

TABLE 4

Preparation of the Components

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

The topcoat inkjet printing compositions were prepared separately by mixing the ingredients listed in tables 2-3 using Dispermat (LC 220-12) at room temperature and 1000rpm for 10 minutes.

The viscosity of the compositions was independently measured on a Brookfield viscometer (model "DV-I Prime" at 100rpm for UV-Vis curable screen-printed compositions, spindle S27, and 50rpm for top-coat inkjet printed compositions, spindle S00) at 25 ℃ and is provided in tables 1-4.

Method for producing optical effect layer

Optical Effect Layers (OEL) have been prepared according to the process (E1-E21) of the invention and according to the comparative process (C1-C11). Tables 5A-C provide the following summaries: i) A combination of compositions used in the printing process, ii) a drawing which schematically illustrates the process itself, iii) a substrate on which the UV-Vis curable screen-printing composition is applied, and iv) the number of passes over the magnetic field generating means during magnetic biaxial orientation.

TABLE 5A

TABLE 5B

TABLE 5C

Wherein the base material (x 20) No. 1-3 is the following base material:

substrate No. 1 is a polymeric substrate (Guardian) ^TM From the CCL Secure),

substrate No. 2 is letter paper (Louisensanal BNP paper 100 g/m) ² )，

Substrate No. 3 is letter paper (Louisentical BNP paper 100 g/m) ² ) Coated by manual screen printing using a T90 screen with a primer composition disclosed in table 4 (primer thickness 20 μm) cured by UV radiation (two lamps: iron-doped mercury lamp 200W/cm from IST Metz GmbH ² 200W/cm mercury lamp ² (ii) a2 passes, 100 m/min).

In fig. 2A (method according to the invention), the method comprises the following steps:

step a)(not shown in the figure): screen printing a UV-Vis curable screen-printing composition onto a substrate (220) to form a coating (210),

after the step a) has been carried out,step b): at least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented,

after the step b) of the process,step c): ink jet printing the top-coated ink jet printing composition to form indicia (230), an

After the step c) of the process,step d): the coating (210) and the mark (230) are cured with a curing unit (250) to form an optical effect layer.

For all the examples (E6, E11, E16 and 21) prepared according to the process of the invention, about 1.2 seconds occurred between step b) and step c). For the examples (E6, E11, E16 and 21) prepared according to the process of the invention, less than 10 seconds occurred between step c) and step d).

In fig. 2B (method according to the invention), the method comprises the following steps:

step a)(not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (220) to form a coating (210),

after the step a) has been carried out,step b):at least a portion of the magnetic or magnetizable pigment particles are biaxially oriented,

after the step b) of the process,step c): ink jet printing a topcoat ink jet printing composition to form indicia (230), and

after the step c) of the process,step d): the coating (210) and the mark (230) are cured with a curing unit (250) to form an optical effect layer.

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

In fig. 2C (method according to the invention), the method comprises the following steps:

step a) (not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (220) to form a coating (210),

after the step a) has been carried out,step b)Comprising two steps, wherein a first step b 1) comprises biaxially orienting at least a part of the magnetic or magnetizable pigment particles, and a subsequent step b 2) uniaxially reorienting at least a part of the magnetic or magnetizable particles,

after the step b) of the process,step c): ink jet printing the top-coated ink jet printing composition to form indicia (230), an

After the step c) of the process,step d): the coating (210) and the mark (230) are cured with a curing unit (250) to form an optical effect layer.

For all examples (E5, E10, E15 and E20)) prepared according to the process of the invention, about 1.2 seconds occurred between step b 2) and step c). For examples E5, E10, E15 and E20 prepared according to the process of the invention, about 1.2 seconds occurred between step c) and step d).

In fig. 4A (comparative method), the method includes the steps of:

step a)(not shown in the figures): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step a) has been carried out,step c): ink jet printing a topcoat of an ink jet printing composition to form indicia (430), an

After the step c) of the process,step d): the coating (410) and the mark (430) are cured with a curing unit (450) to form an optical effect layer.

For all examples (C1 and C6) prepared according to this comparative method, about 1.2 seconds occurred between step C) and step d).

Fig. 4B (comparative method), the method comprising the steps of:

step a)(not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step a) has been carried out,step c): ink jet printing the top coat with an ink jet printing composition to form indicia (430),

after the step c) of the process,step b):biaxially orienting at least a part of the magnetic or magnetizable pigment particles, and

after the step c) of the process,step d): the coating (410) and the indicia (430) are cured to form an optical effect layer.

For all the examples (C2 and C7) prepared according to this comparative method, about 10 seconds occurred between step C) and step b), and about 2.4 seconds occurred between step b) and step d).

Fig. 4C (comparative method), the method comprising the steps of:

step a) (not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step a) has been carried out,step b)/b 1): biaxially orienting at least a part of the magnetic or magnetizable pigment particlesIn the direction of the air flow,

after the step/b 1) of the process,step c): the inkjet printing topcoat applies the inkjet printing composition to form indicia (430),

after the step c) of the process,step b 2): reorienting at least a portion of the magnetic or magnetizable pigment particles uniaxially, and

after the step b 2) has been carried out,step d): the coating (410) and the indicia (430) are cured with a curing unit (450) to form an optical effect layer.

For all the examples (C3 and C8) prepared according to this comparative method, about 0.3 seconds occurred between step b 1) and step C), about 1.2 seconds occurred between step C) and step b 2), and about 3.2 seconds occurred between step b 2) and step d).

Fig. 4D (comparative method), the method comprising the steps of:

step a) (not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step a) has been carried out,step b 1): biaxially orienting at least a part of the magnetic or magnetizable pigment particles, and

after step b)/b 1) of the process,step c): ink jet printing the top coat with an ink jet printing composition to form indicia (430),

after the step c) of the process,step b 2): reorienting at least a portion of the magnetic or magnetizable pigment particles uniaxially, and

simultaneously with part of step b)/b 2),step d): the coating (410) and the indicia (430) are cured with a curing unit (450) to form an optical effect layer.

For all the examples (C4 and C9) prepared according to this comparative method, about 0.3 seconds occurred between step b 1) and step C), and about 1.2 seconds occurred between steps C) and b 2).

Fig. 4E (comparative method), the method comprising the steps of:

step a) (not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step a) has been carried out,step b): at least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented,

partially simultaneously with step B) (i.e., while maintaining the substrate (420) in the magnetic field (B1) of the magnetic field generating means),step c): the inkjet printing topcoat applies the inkjet printing composition to form indicia (430),

partially simultaneously with step B) (i.e., while maintaining the substrate (420) in the magnetic field (B1) of the magnetic field generating means) but after step c),step d): the coating (410) and the indicia (430) are cured with a curing unit (450) to form an optical effect layer.

For all examples (C5 and C10) prepared according to this comparative method, about 2.2 seconds occurred between step C) and step d).

Fig. 4F (comparative method), the method comprising the steps of:

step (ii) of(not shown in the figure): screen printing a UV-Vis curable screen printing composition onto a substrate (420) to form a coating (410),

after the step of the method,step b): at least a portion of the magnetic or magnetizable pigment particles are uniaxially oriented,

simultaneously with part of step B) (i.e., while maintaining the substrate (420) in the magnetic field (B1) of the magnetic field generating means),step d): curing the coating (410) with a curing unit,

after the step d) of the said step,step c):the inkjet printing topcoat applies the inkjet printing composition to form indicia (430),

after the said step c) has been carried out,the method comprises the following steps:the mark (430) is cured with a curing unit.

For the example prepared according to this comparative method (C11), about 5 seconds occurred between the last two steps.

Screen printing of UV-Vis curable Screen-printing compositions

The UV-Vis curable screen-printing compositions described in tables 1-3 were independently applied onto a substrate (x 20) (70 mm x 70 mm) described in table 5 by hand screen printing using a T90 screen, forming a coating (x 10) having the following dimensions: 25mm by 25mm and a thickness of about 20 μm.

Magnetic orientation of UV-Vis curable Screen-printing compositions

After the screen printing step described herein, a step of exposing the coating layer (x 10) to a magnetic field of a magnetic field generating device described later is performed to orient at least a part of the magnetic or magnetizable pigment particles.

Magnetic field generating device for biaxial orientation (shown in FIG. 3)

The magnetic field generating means for biaxially orienting at least a part of the magnetic or magnetizable pigment particles comprise a) a first set (S1) and a second set (S2), the first set (S1) comprising a first rod-shaped dipole magnet (371) and two second rod-shaped dipole magnets (372) _a And 372 _b ) The second group (S2) includes a first rod-shaped dipole magnet (371) and two second rod-shaped dipole magnets (372) _a And 372 _b ) (ii) a And b) a pair (P1) of third rod-like dipole magnets (373) _a And 373 _b )。

The uppermost surface of the first rod-shaped dipole magnet (371) of the first and second groups (S1, S2), and the second rod-shaped dipole magnet (372) of the first and second groups (S1, S2) _a And 372 _b ) And a pair (P1) of third rod-like dipole magnets (373) _a And 373 _b ) Are flush with each other.

A third bar-shaped dipole magnet (373) _a ) And a second bar-shaped dipole magnet (372) of the first group (S1) _a ) And a second group (S2) of second rod-like dipole magnets (372) _a ) Aligned to form a line. A third rod-shaped dipole magnet (373) _b ) And a second bar-shaped dipole magnet (372) of the first group (S1) _b ) And a second group (S2) of second rod-shaped dipole magnets (372) _b ) Aligned to form a line.

The first rod-shaped dipole magnets (371) of the first and second sets (S1, S2) have the following dimensions: having the following dimensions: the first thickness (L1) is 5mm, the first length (L4) is 60mm and the first width (L5) is 40mm. A second bar-shaped dipole magnet (372) of the first and second groups (S1, S2) _a And 372 _b ) Each having the following dimensions:the second thickness (L2) is 10mm, the second length (L6) is 40mm and the second width (L7) is 10mm. A third rod-shaped dipole magnet (373) of the pair (P1) _a And 373 _b ) Each having the following dimensions: the third thickness (L3) is 10mm, the third length (L8) is 20mm and the third width (L9) is 10mm.

A first bar-shaped dipole magnet (371) of the first group (S1) and a second bar-shaped dipole magnet (372) of the first group (S1) _a And 372 _b ) Aligned to form a column, and a second group (S2) of first rod-shaped dipole magnets (371) and a second group (S2) of second rod-shaped dipole magnets (372) _a And 372 _b ) Aligned to form a column. For each set (S1, S2) and each column described herein, a first bar dipole magnet (371) and two second bar dipole magnets (372) _a And 372 _b ) Spaced apart by a second distance (d 2) of 2mm. For each line described herein, a third rod-shaped dipole magnet (373) _a And 373 _b ) And two second rod-shaped dipole magnets (372) _a ) Spaced apart by a third distance (d 3) of 2mm.

The magnetic axes of the first rod-shaped dipole magnets (371) of the first and second sets (S1, S2) are oriented substantially parallel to the base material (320), wherein the magnetic direction of the first rod-shaped dipole magnets (371) of the first set (S1) is opposite to the magnetic direction of the first rod-shaped dipole magnets (371) of the second set (S2), and are separated by a first distance (d 1) of 24mm (corresponding to the sum of the third length (L8) and the two third distances (d 3)).

Two second rod-like dipole magnets (372) of first and second sets (S1, S2) _a And 372 _b ) Is oriented substantially perpendicular to the first plane and substantially perpendicular to the substrate (320). A first group (S1) of second rod-shaped dipole magnets (372) _a ) Directed toward the first plane and toward the substrate (320), a first set (S1) of second rod-like dipole magnets (372) _b ) Is directed toward the substrate (320), and the north pole of the first rod-shaped dipole magnet (371) of the first group (S1) is directed toward the second rod-shaped dipole magnet (372) of the first group (S1) _b ). A second group (S2) of second rod-shaped dipole magnets (372) _a ) Directed towards the first plane and towards the substrate (320), a second set (S2) of second rod-like dipole magnets (372) _b ) OfThe north pole of the first bar-shaped dipole magnet (371) of the second group (S2) is directed to the second bar-shaped dipole magnet (372) of the second group (S2) with the pole directed to the base material (320) _a )。

A third bar-shaped dipole magnet (373) _a ) Directed south to the second rod-shaped dipole magnet (372) of the first set (S1) _a ) Said second rod-like dipole magnet (372) _a ) Directed towards the substrate (320); and a third rod-shaped dipole magnet (373) _b ) Is directed to the second bar-shaped dipole magnet (372) of the first group (S1) _b ) Said second rod-like dipole magnet (372) _b ) Is directed towards the substrate (320).

A first rod-shaped dipole magnet (371) of the first and second groups (S1, S2), a second rod-shaped dipole magnet (372) of the first and second groups (S1, S2) _a And 372 _b ) And a third rod-shaped dipole magnet (373) of the pair (P1) _a And 373 _b ) Made of NdFeB N42 and embedded in a non-magnetic support matrix (not shown) made of Polyoxymethylene (POM), having the following dimensions: 115 mm. Times.115 mm. Times.12 mm.

During magnetic orientation, a substrate (320) carrying a coating (310) is arranged on a non-magnetic back plate made of the above POM, wherein the coating (310) faces the environment, thereby forming an assembly, wherein the non-magnetic back plate (340) has the following dimensions: 180mm x 130mm x 2mm and comprises a centrally aligned hole (48 mm x 48 mm), wherein the coating (310) faces the magnetic field generating means (300). The assembly was moved back and forth as described in table 5, near and above the magnetic field generating device (300), at a distance of about 2mm from the upper surface of the device.

Magnetic field generating device for uniaxial orientation

The magnetic field generating means for uniaxially orienting at least a part of the magnetic or magnetizable pigment particles comprise rod-shaped dipole magnets having a length of about 30mm, a width of about 24mm and a thickness of about 6mm, wherein the rod-shaped dipoles are embedded in a matrix made of POM and having the following dimensions: 40mm by 15mm. The north-south magnetic axis of the bar dipole magnet is parallel to the substrate (x 20) surface and parallel to the width. The rod-shaped dipole magnet was made of NdFeB N42.

During magnetic orientation, the substrate (x 20) carrying the coating (x 10) is arranged on a non-magnetic back plate made of POM as described above, with the coating (x 10) facing the environment, thus forming an assembly. The assembly was placed near and above the magnetic field generating device so that the distance of the base material (x 20) from the upper surface of the bar-shaped dipole magnet was about 6mm.

For the method shown in fig. 2A, 2C and 4C (the means for generating the magnetic field B2 in fig. 2C and 4C), the magnetic field generating means was removed perpendicularly from the surface of the substrate (x 20) opposite to the surface of the support layer (x 10) before the following steps were performed.

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

Ink jet printing of topcoat ink jet printing compositions

Separately applying the topcoat inkjet printing compositions described in tables 1-3 by DOD inkjet printing using a Kyocera KJ4A-TA print head (600 dpi) to form rectangular shaped marks having the following dimensions: 20 mm. Times.12 mm.

For examples E1 to E18 and comparative examples C1 to C11, at about 4g/m ² Each topcoat composition is applied.

For examples E19-E21 (halftone ink jet printing of topcoat compositions), at about 0.4g/m ² About 2.0g/m ² About 4.1g/m ² And about 8.1g/m ² The topcoat compositions were applied separately (see the picture in fig. 5E, rectangle from top to bottom).

Curing the coating (x 10) made of a UV-Vis curable Screen-printing composition and the marking (x 30) made of a Top-coated ink-jet printing composition

Coatings (x 10) made from the UV-Vis curable screen-printing compositions described in tables 1-3 and markings made from the topcoat inkjet printing compositions were made by exposure to UV-LED lamps from Phoseon (Type FireLine 125X 20mm,395nm, 8W/cm) ² ) About 0.5 seconds to cure.

Coating (x 10) of comparative example C11 made from a UV-Vis curable screen-printing composition by exposure to UV-LED lamps from Phoseon(Type FireLine 125×20mm，395nm，8W/cm ² ) About 0.5 seconds to cure, and the C11 indicia made from the topcoat inkjet printing composition was cured by exposure to about 0.7 seconds (two lamps: iron-doped mercury lamp 200W/cm from IST Metz GmbH ² 200W/cm Mercury lamp ² ) To be cured.

Pictures of the optical effect layers obtained by the method according to the invention and by the comparative method at two different viewing angles (left-30 ℃; right +30 ℃) are provided in fig. 5A-E (fig. 5A corresponds to the example of table 5A; fig. 5B corresponds to the example of table 5B, fig. 5C corresponds to the example of table 5C; fig. 5D corresponds to example E17 of table 5B and E18 of table 5C; fig. 5E corresponds to example E19-E21 of table 5B, the top coating film being printed in halftone).

The comparative method shown in fig. 4A for preparing the examples (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 having randomly oriented particles without exhibiting more than one mark. The optical effect layer obtained by a method lacking the step of exposing the coating (x 10) to the magnetic field of a magnetic field generating means to orient at least a part of the particles prior to the step of applying the topcoat composition in the form of one or more indicia (x 30) on top of the coating (x 10) does not exhibit one or more markings.

A comparative method for making examples (C2 and C7) shown in fig. 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), providing biaxially oriented particles having both the X-axis and the Y-axis substantially parallel to the substrate surface without exhibiting a marked optical effect layer. The optical effect layer obtained by the method wherein the step of exposing the coating layer (x 10) to the magnetic field of the magnetic field generating means is performed after the step of applying the topcoat composition over the coating layer (x 10) in the form of the one or more markings (x 30) so as to orient at least a part of the particles without the need for an intermediate step of at least partially curing the topcoat composition.

A comparative method for making examples (C3, C4, C8 and C9) shown in fig. 4C and 4D, wherein the step of magnetically biaxially orienting at least a portion of the magnetic or magnetizable pigment particles is performed prior to the inkjet printing step, and then the 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 biaxially oriented particles that exhibit rolling bars when the OEL is tilted without exhibiting a marking. The optical effect layer obtained by the method of exposing the coating (x 10) to the magnetic field of the magnetic field generating means to orient at least a part of the particles, carried out after the step of applying the topcoat composition in the form of one or more marks (x 30) on the coating (x 10), does not exhibit one or more marks, without the need of carrying out an intermediate step of at least partially curing after the step of applying the topcoat composition.

A comparative method for preparing examples (C5 and C10) shown in fig. 4E, wherein simultaneously with the inkjet printing step and with the step of at least partially curing, performing the step of orienting at least a portion of the magnetic or magnetizable pigment particles uniaxially (i.e., a method lacking the step of at least partially curing after the inkjet printing step, or a method comprising the 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 uniaxially oriented particles exhibiting rolling rods upon tilting the OEL without exhibiting marking. The optical effect layer obtained by exposing the coating (x 10) to the magnetic field of a magnetic field generating means, thereby orienting at least a part of the particles, is not exhibiting one or more markings, wherein the step of exposing the coating (x 10) to the magnetic field of a magnetic field generating means is performed partially simultaneously with the step of applying the topcoat composition in the form of one or more markings (x 30) on top of the coating (x 10) and simultaneously with the step of at least partially curing.

A comparative method for making example C11, shown in fig. 4F, wherein magnetic or magnetizable pigment particles are oriented and fixed by curing prior to the inkjet printing step, resulting in the optical effect layer exhibiting a rolling bar without exhibiting more than one mark upon tilting the OEL.

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

The method according to the invention for the preparation of the examples (E1-E4, E7-E9, E12-E14 and E17-18) shown in fig. 2B, wherein the step of magnetically biaxially orienting at least a portion of the magnetic or magnetizable pigment particles is carried out before the ink-jet printing step, and then the step of at least partially curing the coating (X10) and the one or more markers (X30) is carried out after the ink-jet printing step, provides biaxially oriented particles having both the X-axis and the Y-axis substantially parallel to the surface of the substrate (X20) and exhibits a marked optical effect layer, thereby providing an optical effect layer having bright and highly reflective areas and markers.

The method according to the invention for the preparation of examples (E5, E10 and E15) shown in fig. 2C, wherein two magnetic orientation steps (i.e. a second step of magnetically uniaxial reorienting at least a part of the magnetic or magnetizable pigment particles after the first step of magnetically biaxial orienting at least a part of the particles) are performed before the inkjet printing step, followed by a step of at least partially curing the coating (x 10) and the one or more markers (x 30) after the inkjet printing step, provides an optical effect layer having biaxially oriented particles which exhibit rolling bars when the OEL is tilted and exhibiting markers, thereby providing an optical effect layer having bright and highly reflective areas and markers.

The method according to the invention for the preparation of examples (E6, E11 and E16) shown in fig. 2A, wherein the step of magnetically uniaxial orienting at least a part of the magnetic or magnetizable pigment particles is performed before the inkjet printing step, and then the step of at least partially curing the coating (x 10) and the one or more markers (x 30) is performed after the inkjet printing step, provides an optical effect layer having uniaxially oriented particles exhibiting rolling rods upon tilting the OEL and exhibiting markers.

As shown in fig. 5A-E, the combination of a UV-Vis curable screen-printing composition comprising magnetic or magnetizable pigment particles for producing a coating (x 10) and a top-coat inkjet printing composition for producing one or more markings with the method according to the invention allows the preparation of optical effect layers exhibiting one or more markings, which may be cationically curable, free-radical curable, or hybrid curable compositions, wherein the OEL may be produced on different kinds of substrates.

Claims (15)

1. A method for producing an Optical Effect Layer (OEL) exhibiting one or more marks (x 30) on a substrate (x 20), the method comprising the steps of:

a) Applying a radiation curable coating composition comprising non-spherical magnetic or magnetizable pigment particles on a surface of a substrate (x 20), the radiation curable coating composition being in a first liquid state, thereby forming a coating layer (x 10);

b) Exposing the coating (x 10) to a magnetic field of a magnetic field generating device, thereby orienting at least a portion of the magnetic or magnetizable pigment particles;

c) After step b), applying a topcoat composition over the coating (x 10), wherein the topcoat composition is applied in the form of one or more indicia (x 30), and

d) Simultaneously with or after step c), at least partially curing the coating (x 10) and the one or more markings (x 30) with a curing unit (x 50).

2. The method according to claim 1, wherein step b) of exposing the coating (x 10) is performed such that at least a part of the non-spherical magnetic or magnetizable pigment particles are uniaxially oriented.

3. Method according to claim 1, wherein step b) of exposing the coating (X10) is carried out such that at least a part of the non-spherical magnetic or magnetizable pigment particles are biaxially oriented, wherein the non-spherical magnetic or magnetizable pigment particles are platelet-shaped magnetic or magnetizable pigment particles having an X-axis and a Y-axis defining the main extension plane of the particles.

4. A method according to claim 3, wherein step b) of exposing the coating layer (X10) is performed such that at least a part of the plate-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.

5. The method according to claim 3 or 4, wherein step b) comprises two steps, a first step b 1) comprising exposing the coating (x 10) to the magnetic field of a magnetic field generating means to biaxially orient at least a part of the flake-like magnetic or magnetizable pigment particles, and a further step b 2) comprising exposing the coating (x 10) to the magnetic field of a second magnetic field generating means to uniaxially orient at least a part of the flake-like magnetic or magnetizable pigment particles, wherein said further step b 2) is performed simultaneously, simultaneously or after step b 1) part.

6. The method of any one of claims 1 to 4, further comprising:

step x): selectively at least partially curing one or more first areas of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second areas of the coating (x 10) remain unexposed to the irradiation; and

step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means,

wherein said step x) is performed partially simultaneously with step c) or after step c), and said step y) is performed after said step x) and partially simultaneously with step d) or before step d).

7. The method of claim 5, further comprising:

step x): selectively at least partially curing one or more first areas of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second areas of the coating (x 10) remain unexposed to the irradiation; and

step y): exposing the coating (x 10) to the magnetic field of a third magnetic field generating means,

wherein said step x) is performed partially simultaneously with step c) or after step c), and said step y) is performed after said step x) and partially simultaneously with step d) or before step d).

8. The method of any one of claims 1 to 4, further comprising:

step x): selectively at least partially curing one or more first areas of the coating (x 10) to fix at least a portion of the magnetic or magnetizable particles in the position and orientation they adopt, such that one or more second areas of the coating (x 10) remain unexposed to the irradiation; and

step y): exposing the coating (x 10) to the magnetic field of a second magnetic field generating means,

wherein said step x) is performed partially simultaneously with step b) or after step b), and said step y) is performed after said step x) and before step c).

9. The method of claim 5, further comprising:

step x): selectively at least partially curing one or more first areas of the coating (x 10) to fix at least a portion of the magnetic or magnetisable particles in the position and orientation they adopt, such that one or more second areas of the coating (x 10) remain unexposed to the radiation; and

step y): exposing the coating (x 10) to the magnetic field of a third magnetic field generating means,

wherein said step x) is performed partially simultaneously with step b) or after step b), and said step y) is performed after said step x) and before step c).

10. The method according to any one of claims 1 to 9, wherein step a) of applying a radiation curable coating composition is performed by a method selected from the group consisting of screen printing, rotogravure printing, pad printing and flexographic printing.

11. The method according to any one of claims 1 to 10, wherein step c) of applying the topcoat composition is performed by a non-contact fluid microdispensing technique, preferably by an inkjet printing method.

12. The method according to any one of claims 1 to 11, wherein at least a part of the non-spherical magnetic or magnetizable particles consists of non-spherical optically variable magnetic or magnetizable pigment particles.

13. The method according to claim 12, wherein the non-spherical optically variable magnetic or magnetizable pigment particles are selected from the group consisting of magnetic thin film interference pigments, magnetic cholesteric liquid crystal pigments and mixtures thereof.

14. The method of any one of claims 1 to 13, wherein the one or more indicia are selected from the group consisting of codes, symbols, alphanumeric symbols, graphics, geometric patterns, letters, words, numbers, logos, pictures, portraits, and combinations thereof.

15. An Optical Effect Layer (OEL) produced by the method of any one of claims 1 to 14.