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BR-112021004243-B1 - PROCESS FOR PRODUCING AN OPTICAL EFFECT LAYER ON A SUBSTRATE, OPTICAL EFFECT LAYER, AND SECURITY DOCUMENT, OBJECT OR DECORATIVE ELEMENT

BR112021004243B1BR 112021004243 B1BR112021004243 B1BR 112021004243B1BR-112021004243-B1

Abstract

PROCESSES FOR PRODUCING OPTICAL EFFECT LAYERS COMPRISING NON-SPHERICAL ORIENTED MAGNETIC OR MAGNETIZABLE PIGMENT PARTICLES. The present invention relates to the field of magnetic assemblies and processes for producing optical effect layers (OELs) comprising magnetically oriented non-spherical magnetic or magnetizable pigment particles on a substrate. In particular, the present invention relates to magnetic assemblies and processes for producing said OELs as anti-counterfeiting means in security documents or security articles or for decorative purposes.

Inventors

  • Nathalie Benninger
  • Evgeny Loginov
  • Claude-Alain Despland
  • Gisèle Baudin

Assignees

  • SICPA HOLDING SA

Dates

Publication Date
20260317
Application Date
20190805
Priority Date
20180910

Claims (15)

  1. 1. Process for producing an optical effect layer (OEL) (x20) on a substrate (x10), characterized in that it comprises the steps of: a) applying to a substrate surface (x10) a first radiation-curable coating composition comprising non-spherical magnetic or magnetizable pigment particles, so as to form one or more first patterns of a first coating layer (x21), said first radiation-curable coating composition being in a first state; b) exposing the first radiation-curable coating composition to a magnetic field of a first magnetic assembly (x00-a) comprising i) a magnetic field generating device (x30) comprising a loop-shaped magnetic field generating device (x31) being a single loop-shaped dipole magnet having a magnetic axis perpendicular to the substrate surface (x10), or a combination of two or more dipole magnets arranged in a loop-shaped arrangement and having a resultant magnetic axis perpendicular to the substrate surface (x10); and ii) a magnetic field generating device (x40) being a single bar dipole magnet having a magnetic axis substantially parallel to the substrate surface (x10) or a combination of two or more bar dipole magnets (x41) having a resultant magnetic axis parallel to the substrate surface (x10); or a magnetic field of a first magnetic assembly (x00-a) comprising i) a magnetic field generating device (x30) comprising a support matrix (x34), a loop-shaped magnetic field generating device (x31) being a single loop-shaped dipole magnet having a magnetic axis perpendicular to the substrate surface (x10), or a combination of two or more dipole magnets arranged in a loop-shaped arrangement, each of the two or more dipole magnets having a magnetic axis perpendicular to the substrate surface (x10) and having the same magnetic field direction, a single dipole magnet (x32) having a magnetic axis perpendicular to the substrate surface (x10) or two or more dipole magnets (x32) having a magnetic axis perpendicular to the substrate surface (x10) and having the same magnetic field direction and/or one or more pole pieces (x33); and ii) a magnetic field generating device (x40) being a single bar dipole magnet having a magnetic axis parallel to the substrate surface (x10) or a combination of two or more bar dipole magnets (x41), each of the two or more bar dipole magnets (x41) having a magnetic axis parallel to the substrate surface (x10) and having the same direction as the magnetic field; or a magnetic field of a first magnetic assembly (x00-a) comprising i) a magnetic field generating device (x30) comprising a support matrix (x34), a loop-shaped magnetic field generating device (x31) being a single loop-shaped magnet or a combination of two or more dipole magnets arranged in a loop-shaped arrangement, the loop-shaped magnetic field generating device (x31) having radial magnetization, a single dipole magnet (x32) having a magnetic axis perpendicular to the substrate surface (x10), or a single dipole magnet (x32) having a magnetic axis parallel to the substrate surface (x10), or two or more dipole magnets (x32), each of said two or more dipole magnets (x32) having a magnetic axis perpendicular to the substrate surface (x10), wherein the north pole of said single dipole magnet (x32) or the north pole of at least one of said two or more dipole magnets (x32) points towards the surface of the substrate (x10) when the north pole of the single loop magnet or of the two or more dipole magnets forming the loop magnetic field generating device (x31) points towards the periphery of said loop magnetic field generating device (x31), or wherein the south pole of said single dipole magnet (x32) or the south pole of at least one of said two or more dipole magnets (x32) points towards the surface of the substrate (x10) when the south pole of the single loop magnet or of the two or more dipole magnets forming the loop magnetic field generating device (x31) points towards the periphery of said loop magnetic field generating device (x31); and ii) a magnetic field generating device (x40) being a single bar dipole magnet having a magnetic axis parallel to the substrate surface (x10), or a combination of two or more bar dipole magnets (x41), each of the two or more bar dipole magnets (x41) having a magnetic axis parallel to the substrate surface (x10) and having the same direction as the magnetic field, so as to orient at least part of the non-spherical magnetic or magnetizable pigment particles; c) at least partially cure the first radiation-curable coating composition of step b) to a second state, so as to fix the non-spherical magnetic or magnetizable pigment particles in their adopted positions and orientations, and so as to form one or more at least partially cured first patterns; d) apply at least partially to the one or more at least partially cured first patterns of step c) a second radiation-curable coating composition comprising non-spherical magnetic or magnetizable pigment particles, so as to form one or more second patterns of a second coating layer (x22), said second radiation-curable coating composition being in a first state; e) exposing the second radiation-curable coating composition to a magnetic field from a second magnetic assembly (x00-b), said second magnetic assembly (x00-b) being selected from the first magnetic assembly (x00-a) of step b), wherein said second magnetic assembly (x00-b) is different from the first magnetic assembly (x00-a) used in step b), and wherein the magnetic direction of the magnetic field generating device (x40) of said magnetic assembly (x00-b) is opposite to the magnetic direction of the magnetic field generating device (x40) of the first magnetic assembly (x00-a) within the reference frame of the substrate (x10); (e) cure at least partially the second radiation-curable coating composition of step (e) to a second state, so as to fix the non-spherical magnetic or magnetizable pigment particles in their adopted positions and orientations, and so as to form one or more second at least partially cured patterns, wherein the optical effect layer gives an optical impression of a loop-shaped body having a size and shape that varies when tilting the optical effect layer.
  2. 2. Process according to claim 1, characterized in that the first magnetic assembly (x00-a) and/or the second magnetic assembly (x00-b) independently comprise: i.1) the magnetic field generating device (x30) comprising a support matrix (x34), the loop-shaped magnetic field generating device (x31) being a single ring-shaped dipole magnet having a magnetic axis perpendicular to the substrate surface (x10), and one or more pole pieces (x33); and i.2) the magnetic field generating device (x40) being two or more bar dipole magnets (x41), each of the two or more bar dipole magnets (x41) having a magnetic axis parallel to the substrate surface (x10) and having the same magnetic field direction; ouii.1) the magnetic field generating device (x30) comprising the support matrix (x34), the loop-shaped magnetic field generating device (x31) being a combination of four or more dipole magnets (x31) arranged in a loop-shaped arrangement, preferably a square-shaped arrangement, each of the four or more dipole magnets (x31) having a magnetic axis parallel to the surface of the substrate (x10), the loop-shaped magnetic field generating device (x31) having radial magnetization, and two or more dipole magnets (x32) having a magnetic axis perpendicular to the surface of the substrate (x10) and having the same magnetic field direction; and ii.2) the magnetic field generating device (x40) being a single bar dipole magnet having a magnetic axis parallel to the substrate surface (x10), wherein the north pole of at least one of said two or more dipole magnets (x32) points towards the substrate surface (x10) when the north pole of the four or more dipole magnets forming the loop-shaped magnetic field generating device (x31) points towards the periphery of said loop-shaped magnetic field generating device (x31), or wherein the south pole of at least one of said two or more dipole magnets (x32) points towards the substrate surface (x10) when the south pole of the four or more dipole magnets forming the loop-shaped magnetic field generating device (x31) points towards the periphery of said loop-shaped magnetic field generating device (x31); and iii) optionally, one or more pole pieces (x50).
  3. 3. Process, according to claim 2, characterized in that the magnetic field generating device (x30) of the first magnetic assembly (x00-a) is placed on top of the magnetic field generating device (x40) of said first magnetic assembly (x00-a); and the magnetic field generating device (x40) of the second magnetic assembly (x00-b) is placed on top of the magnetic field generating device (x30) of said second magnetic assembly (x00-b).
  4. 4. Process, according to claim 1 or 2, characterized in that the first magnetic assembly (x00-a) comprises: i) the magnetic field generating device (x30) comprising the support matrix (x34), the loop-shaped magnetic field generating device (x31) being a single ring-shaped dipole magnet having a magnetic axis perpendicular to the substrate surface (x10) and one or more pole pieces (x33); and ii) the magnetic field generating device (x40) being two or more bar dipole magnets (x41), each of the two or more bar dipole magnets (x41) having a magnetic axis parallel to the substrate surface (x10) and having the same magnetic field direction; wherein the second magnetic assembly (x00-b) comprises: i) the magnetic field generating device (x30) comprising the support matrix (x34), the loop-shaped magnetic field generating device (x31) being a combination of four or more dipole magnets arranged in a loop-shaped arrangement, preferably a square-shaped arrangement, each of the four or more dipole magnets having a magnetic axis parallel to the surface of the substrate (x10), the loop-shaped magnetic field generating device (x31) having radial magnetization, two or more dipole magnets (x32) having a magnetic axis perpendicular to the surface of the substrate (x10) and having the same magnetic field direction, wherein the north pole of at least one of said two or more dipole magnets (x32) points towards the surface of the substrate (x10) when the north pole of the four or more dipole magnets forming the loop-shaped magnetic field generating device (x31) points towards the periphery of said magnetic field generating device. magnetic loop-shaped (x31), or wherein the south pole of at least one of said two or more dipole magnets (x32) points towards the surface of the substrate (x10) when the south pole of the four or more dipole magnets that form the loop-shaped magnetic field generating device (x31) points towards the periphery of said loop-shaped magnetic field generating device (x31); ii) the magnetic field generating device (x40) being a single bar dipole magnet having a magnetic axis substantially parallel to the surface of the substrate (x10); and iii) optionally, one or more pole pieces (x50).
  5. 5. Process, according to claim 4, characterized in that the magnetic field generating device (x30) of the first magnetic assembly (x00-a) is placed on top of the magnetic field generating device (x40) of said first magnetic assembly (x00-a); and the magnetic field generating device (x40) of the second magnetic assembly (x00-b) is placed on top of the magnetic field generating device (x30) of said second magnetic assembly (x00-b).
  6. 6. A process according to any one of claims 1 to 5, characterized in that at least one of step a) or step d) is carried out by a printing process selected from the group consisting of screen printing, rotogravure printing and flexographic printing.
  7. 7. A process according to any one of claims 1 to 6, characterized in that at least a portion of the plurality of non-spherical magnetic or magnetizable pigment particles consists of non-spherical optically variable magnetic or magnetizable pigment particles.
  8. 8. A process according to any one of claims 1 to 7, characterized in that the non-spherical magnetic or magnetizable pigment particles are the same in the first radiation-curable coating composition and in the second radiation-curable coating composition, or in that the non-spherical magnetic or magnetizable pigment particles differ in terms of at least one size or color property in the first radiation-curable coating composition and in the second radiation-curable coating composition.
  9. 9. A process according to any one of claims 1 to 8, characterized in that non-spherical magnetic or magnetizable pigment particles are present in an amount from 2% by weight to 40% by weight in the first radiation-curable coating composition, and non-spherical magnetic or magnetizable pigment particles are present in an amount from 2% by weight to 40% by weight in the second radiation-curable coating composition.
  10. 10. Process, according to any one of claims 1 to 9, characterized in that non-spherical magnetic or magnetizable pigment particles are present in the same quantity in the first radiation-curable coating composition and in the second radiation-curable coating composition.
  11. 11. A process according to any one of claims 1 to 10, characterized in that step c) is carried out partially simultaneously with at least one of the steps b) or step f) is carried out partially simultaneously with step e).
  12. 12. A process according to any one of claims 1 to 11, characterized in that the non-spherical magnetic or magnetizable particles are platelet-shaped pigment particles, wherein said process further comprises a step of exposing the radiation-curable coating composition to a dynamic magnetic field of a magnetic field generating device, so as to biaxially orient at least a portion of the platelet-shaped magnetic or magnetizable pigment particles, said step being performed after step a) and before step b), and/or said step being performed after step d) and before step e).
  13. 13. Process, according to any one of claims 1 to 12, characterized in that the shape of one or more first patterns of the first coating layer (x21) and the shape of one or more second patterns of the second coating layer (x22) independently represent one or more indications, points and/or lines.
  14. 14. Optical effect layer (OEL) (x20), characterized in that it is produced by the process as defined in any one of claims 1 to 13.
  15. 15. Security document, object or decorative element, characterized in that it comprises one or more optical effect layers (OELs) (x20) as defined in claim 14.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the field of protecting valuable documents and valuable commercial goods against counterfeiting and illegal reproduction. In particular, the present invention relates to optical effect layers (OELs) exhibiting a loop-shaped optical effect dependent on the viewing angle, magnetic assemblies and processes for the production of said OELs, as well as uses of said optical effect layers as an anti-counterfeiting means for documents. BACKGROUND OF THE INVENTION [0002] The use of inks, coating compositions, coatings or layers containing magnetizable or magnetic pigment particles, in particular non-spherical optically variable magnetic or magnetizable pigment particles, for the production of security elements and security documents is known in the art. [0003] Security features, for example, for security documents, can be classified into "secret" and "open" security features. The protection offered by secret security features is based on the concept that these features are hidden, usually requiring specialized equipment and knowledge for their detection, whereas "open" security features are easily detectable with unaided human senses, for example, these features may be visible and/or detectable through tactile senses, although they are still difficult to produce and/or copy. However, the effectiveness of open security features largely depends on their easy recognition as a security feature, because users will only perform a security check based on that security feature if they are aware of its existence and nature. [0004] Coatings or layers comprising oriented magnetic or magnetizable pigment particles are disclosed, for example, in US documents 2,570,856; US 3,676,273; US 3,791,864; US 5,630,877 and US 5,364,689. Magnetic or magnetizable pigment particles in coatings allow the production of magnetically induced images, designs and/or patterns through the application of a corresponding magnetic field, causing a local orientation of the magnetic or magnetizable pigment particles in the unhardened coating, followed by hardening of the latter. This results in specific optical effects, i.e., magnetically induced fixed images, designs or patterns highly resistant to counterfeiting. Security elements based on oriented magnetic or magnetizable pigment particles can only be produced by having access to magnetic or magnetizable pigment particles or to a corresponding paint or composition comprising said particles, and the specific technology employed to apply said paint or composition and orient said pigment particles in the applied paint or composition. [0005] Moving ring effects have been developed as efficient security features. Moving ring effects consist of optically illusory images of objects such as funnels, cones, bowls, circles, ellipses, and hemispheres that appear to move in any x-y direction, depending on the tilt angle of said optical effect layer. Methods for producing moving ring effects are disclosed, for example, in documents EP 1 710 756 A1, US 8,343,615, EP 2 306 222 A1, EP 2 325 677 A2, and US 2013/084411. [0006] Document WO 2011/092502 A2 discloses an apparatus for producing moving ring images that exhibit an apparently moving ring with changing viewing angle. The disclosed moving ring images can be obtained or produced using a device that allows the orientation of magnetic or magnetizable particles with the aid of a magnetic field produced by the combination of a soft magnetizable sheet and a spherical magnet having its north-south axis perpendicular to the plane of the coating layer and disposed below said soft magnetizable sheet. [0007] The moving ring images of the prior art are generally produced by aligning the magnetic or magnetizable particles according to the magnetic field of only one rotating or static magnet. Since the field lines of a single magnet generally bend relatively smoothly, i.e., have low curvature, the change in orientation of the magnetic or magnetizable particles is also relatively smooth on the surface of the OEL. Additionally, the magnetic field strength decreases rapidly with increasing distance from the magnet when only a single magnet is used. This makes it difficult to obtain a highly dynamic and well-defined feature through the orientation of the magnetic or magnetizable particles, and can result in visual effects that display blurred ring edges. [0008] Document WO 2014/108404 A2 discloses optical effect layers (OELs) comprising a plurality of magnetically oriented non-spherical magnetic or magnetizable particles dispersed in a coating. The specific magnetic orientation pattern of the disclosed OELs provides the viewer with the optical effect or impression of a loop-shaped body moving after tilting the OEL. Furthermore, document WO 2014/108404 A2 discloses OELs exhibiting an optical effect or impression of a protrusion in the central area of the loop-shaped body, said protrusion being caused by a reflection zon