WO2024218531A1

WO2024218531A1 - Magnetic alignment of magnetically orientable pigments in an ink with superimposed magnetic fields.

Info

Publication number: WO2024218531A1
Application number: PCT/IB2023/053137
Authority: WO
Inventors: Lars Hoffmann; Muhammad Sajjad RAZA; Muhammad Imran ABBAS
Original assignee: Htc Technology Consulting; Ultracoat Pakistan
Priority date: 2023-04-20
Filing date: 2023-04-20
Publication date: 2024-10-24

Abstract

The invention describes an arrangement of magnetic fields for aligning magnetically orientable pigments in a printing ink. The arrangement creates two different mutual orthogonal reflection patterns in an optical effect layer (OEL) resulting from the magnetic orientation with at least two superimposed magnetic fields. This easily detectable effect allows the use of such an OEL as a security feature for valuable documents such as banknotes and identity documents or security labels as well as for decorative articles. The present invention provides security documents and decorative articles containing such OELs, as well as methods for producing these OELs.

Description

Magnetic alignment of magnetically orientable pigments in an ink with superimposed magnetic fields.

The invention relates to the field of printing technology, in particular to the printing of security elements. More specifically, the invention relates to devices for aligning magnetically orientable pigments in a printing ink, a printing machine equipped with such devices and an associated printing process. Finally, the invention relates to a data carrier with a coating consisting of a magnetic aligned ink attached on its surface.

Data carriers such as banknotes and other valuable documents, which are used as admission tickets, travel tickets or for identifying and authorizing people, as well as money cards or as security and brand labels, are used to protect values against product counterfeiting and piracy in order to achieve sufficient protection against forgery. Usually they are equipped with various security elements. These security elements can, for example, be elements such as watermarks or security threads or layers laminated onto the substrate of the data carrier to be secured. Security elements that are applied to the surface of the data carrier by means of printing and/or as a transfer element are widely used.

Security elements on the surface of a data carrier to be secured can usually be recognized visually and can therefore be checked directly with the naked eye without the aid of special equipment.

In this context, the use of magnetically orientable pigments in an ink is already known. Magnetically orientable inks are used for an optical attractive printing. It is known in the art to use magnetically orientable pigments in printing inks or coatings to allow the production of magnetically induced images, designs and/or patterns through the application of a correspondingly structured magnetic field, inducing a local orientation of the magnetically orientable pigments.

Materials and technologies for the orientation of magnetically orientable pigments in coating compositions have been disclosed for example in US 2,418,479; US 2,570,856; US 3,676,273; US 5,630,877; US 6,103,361; EP 0 406 667 B1; US 2002 / 0160194; US 2004 / 0009308; EP 0 710 508 A1; WO 2003 / 000801 A2; WO 2006 / 061301 A1. Coatings or layers comprising oriented magnetic color-shifting pigment particles, resulting in particularly appealing optical effects, useful for the protection of security documents, have been disclosed in WO 2005 / 002866 A1. As described for example in WO 2015 / 018663 A1, it is known in the art that high contrast, brightness and reflectivity are essential for overt security features comprising of magnetically oriented pigments with non-spherical shape.

Patent specification EP 0 556 449 B1 refers to the use of non-spherical magnetic particles which, by means of magnetic fields applied over a large area, exhibit a transmission characteristic after orientation in the ink matrix which influences the reflection of incident light. According to this patent specification, the decisive factor here is the use of two magnetic particles in the ink, which align themselves in the applied field either parallel or perpendicular in the ink. The alignment of the magnetic particles and the curing of the ink carrier take place simultaneously. The magnetic arrangements used are configured specifically for the application and cannot be changed individually. In terms of equipment, the application is limited to piece goods.

The creation of a print with magnetically aligned particles that reflect light in two directions is described in patent specification WO 2004 / 007095 A2. Here, the different reflection direction is achieved by a special magnetization. The resulting image is two-dimensional and not individualized.

WO 2002 / 090002 A2 describes the magnetic alignment of nearly planar pigments and the resulting possible application for pigments with interference coating. In this application, the alignment of the pigments is combined with a color effect depending on the viewing angle. Special motion effects result, which are coupled to the special pigments, when viewed at different angles.

EP 2 314 386 A1 and DE 10 2004 035 866 A1 describe the alignment of magnetizable particles in an ink in the rotary printing processes letterpress, gravure and offset. For alignment, magnetizable plates and/or electromagnets are combined in the printing unit, with at least one variable magnetizable element being involved. Printing is done on sheets.

DE 10 2005 0199 19 A1 and US 8,263,191 B12 describe the alignment of magnetizable colored pigments with a device in which a magnetic pattern is inscribed on a continuously magnetizable printing form. This printing form is in direct contact with the substrate on which the ink containing the magnetizable pigments is applied by means of tape transport. Hardening takes place during the contact time of the uncured inks with the magnetizing device.

US 3,853,676 describes printing onto a substrate with a film comprising film-forming material and magnetically orientable pigments that is oriented in curved configurations and located in close proximity to the film, and that can be seen by the naked eye to provide awareness to the viewer of the location of the film.

US 5,364,689 discloses a method and an apparatus for producing a magnetically formed pattern. The magnetically formed pattern becomes visible on the surface of the coated product as the light rays incident on the ink layer are reflected or absorbed differently by magnetic particles arranged in a shape corresponding to a desired pattern.

US 6,808,806 discloses methods and devices for producing images on coated articles. The methods generally include applying a layer of magnetizable pigment coating in liquid form on a substrate, with the magnetizable pigment coating containing a plurality of magnetic non-spherical particles or flakes. A magnetic field is subsequently applied to selected regions of the pigment coating while the coating is in liquid form, with the magnetic field altering the orientation of selected magnetic particles or flakes. Finally, the pigment coating is solidified, affixing the reoriented particles or flakes in a non-parallel position to the surface of the pigment coating to produce an image such as a 3-dimensional-like image on the surface of the coating. The pigment coating can contain various interference or non-interference magnetic particles or flakes, such as magnetic color shifting pigments.

US 7,517,578 describes embodiments which provide optical illusiveness, created by substantially parallel aligned non-spherical magnetic pigments. A combination of two different main directions of alignment of the pigments yields maximum optical reflectivity in two different distinct viewing angles creating an optical "flip-flop", i.e. a switch between high and low reflection on two adjacent printed areas with tilting the carrier of the printed optical effect layer.

US 8,025,952 discloses a coating of pigments overlaying a printed image on a security device, wherein said pigments are magnetically aligned with a substantially parallel orientation in such a manner as to obscure the image forming a latent image when viewing the security device from a first angle, and to reveal the image when viewing the security device from a different angle. According to the magnetic orientation pattern of the magnetic or magnetizable pigments a coated layer with oriented magnetic pigments displays bright and dark areas depending on the angle of observation. The reflectivity of specific zones of the coated layer is directly dependent on the orientation of the magnetic or magnetizable pigments in the coating layer.

EP 2 484 455 B1 discloses jointly visible zones of a first and second hardened coating compositions comprising pigments oriented to imitate a first and a second curved surfaces. As disclosed in EP 2 484 455 B1 and WO 2004 / 007095 A2, coating compositions comprising pigments oriented to imitate a curved surface produce a specular reflection zone that would be seen by an observer as a bright zone moving upon tilting the substrate carrying the coating composition (i.e. upon varying the direction of observation) an effect known as “rolling-bar”.

EP 2 846 932 B1 discloses coatings with platelet-shaped magnetic or magnetizable pigments oriented such as to display a pattern of bright and dark areas which appear to move, or to appear and disappear when the viewing angle of the optical effect layer changes. The particles have their maximum reflectivity (maximum projection area) in a direction perpendicular to their extended surface.

WO 2022 / 049 024 A1 discloses angles of orientation of substantially parallel aligned magnetic or magnetizable platelet-shaped pigments, which yield bright optical reflectivity in directions of observation applicable for evaluation by the naked eye. The same angles of orientation already are the fundamental basis for the earlier US 7,517,578 or US 8,025,952.

To create more sophisticated optical effects created by the reflectivity of aligned magnetic or magnetizable pigments depending on the direction of observation, it is known in the art to create special magnet assemblies built of two or more magnets. WO 2019 / 038 369 discloses a rotatable magnet assembly overlapping other magnetic fields from dipole magnets to create rotational symmetric alignment of the pigments in a coating.

WO 2020 / 052862 discloses the superimposition of magnetic fields to create a “rotative” effect in the coating aligned by these static magnetic fields. Rotational symmetric magnetic alignment is created by setups of at least two rotational symmetric magnets. The process of printing an ink and alignment of the magnetic pigments is run in a consecutive process.

US 7,674,501 describes a process of a two-stage magnetic alignment of an ink, with different inks printed in consecutive steps. The inks may differ in concentration of magnetic or magnetizable pigments. With this variation, the optical appearance of the coating is dependent on the direction of observation.

WO 2016 / 026 896 discloses a magnetic setup to align magnetic pigments in an ink built-up of an arrangement of permanent magnets to be rotated by an electrical motor. WO 2012 / 104 098 discloses a process of consecutive printing and aligning coatings with magnetic or magnetizable pigments in at least two steps in a way to create two so called “rolling bar” effects with oncoming running directions.

WO 2021 / 239607 A1 discloses a magnetic setup to align magnetic or magnetizable pigments in a coating in a biaxial parallel orientation in order to yield a bright reflectivity for a defined angle of observation. A multiple-stage printing and hardening process is described.

WO 2021 / 083808 discloses a multilayer arrangement of magnets. With this magnetic or magnetizable pigments in a coating are aligned to yield bright signs as small letters, depending on the angle of observation.

DE 10.2013.015.277 discloses a way of creating illusive 3-dimensional arrangement of magnetic or magnetizable pigments in an ink by the use of magnetized rubber plates.

WO 2008 / 046702 discloses a combination of two magnetic bars. One of the two carries engraved structures, the second magnetic bar is adhered in direct contact below. The superimposition of the two magnetic fields results in a 3-dimensional field pattern.

Application PCT / EP 2013 / 058986 discloses a mathematic description of monotonically decreasing or increasing magnetic field intensities resulting from superimpositions like disclosed in WO2008 / 046702.

The devices known in the art for orienting magnetically orientable particles in an ink still have various disadvantages that need to be overcome. In general, the orientation of the pigments is difficult to adjust or the referring magnet assemblies are very complex. In consequence the devices are expensive and the orientation patterns produced are inflexible or hardly allow customer-specific individualization.

For securing banknotes, identity documents or product and brand production today in the majority of applications 3-dimensional alignment of magnetically orientable pigments or clearly defined low and high reflection effects like the “flip-flop” or the “rolling bar” effects are in use. Since the latter two have been used for many years there have been found many forged documents. The fakes imitate the high intense and low intense reflection effect (e.g. “flip-flop” or “rolling bar”) by printing with inks showing reflectivity of different intensity. Such fraud attempt does not withstand a thorough evaluation of the security feature but is still similar enough compared to the real security feature to deceive the man in the street at first sight. In the recent years the security of these features has diminished too far to still be estimated as capable of securing sensitive documents of value on a high level. At the same time the state of the art process in the production of the mainly used rolling bar and flip-flop feature is very complicated and expensive due to the tools needed and due to the disadvantage, that production speed has to be reduced in order to achieve good visible features.

Disclosure of the Invention

The task of the invention is solved by the subject of the independent patent claims. Advantageous embodiments of the invention emerge from the dependent claims.

It is the object of the present invention to overcome the disadvantages of the prior art and to provide an improved method for aligning magnetically orientable pigments in an ink. The invention is intended to enable a variety of embodiments and thus to make it possible to individually and reproducibly equip data carriers with a high degree of security against forgery. The aim of this invention is to create a security feature with an easily recognizable special optical effect. The optics originate from a combination of two reflection intensity patterns resulting from the magnetically alignment of pigments with at least two superimposed magnetic fields. This superimposition of magnetic fields is induced in an OEL. (Optical Effective Layer. In the context of the invention an ink layer with pigments, magnetically oriented in a superimposed magnetic field). The special feature of the superimposition is that the OEL shows two different reflection patterns in two perpendicular observation directions. The overall reflection pattern created with the invention has two mutual orthogonal main optical active axes. In the context of the invention, the main optical active axis is the direction of a clearly visible change in reflection intensity emanating from the pattern of magnetically aligned pigments.

The invention discloses the superimposition of magnetic fields for the alignment of magnetically orientable pigments in an ink and a device that causes such an superimposition in the independent claims of the invention. The superimposition of the magnetic fields results in a special alignment of magnetically orientable pigments in a printing ink. The optical appearance of this alignment is characterized by its reflection pattern that is defined by two different reflection patterns perpendicular to each other. These two patterns are e.g. of the type of a dynamic 3-dimensional reflection and e.g. a reflection intensity maximum that changes into a reflection intensity minimum depending on the viewing angle. The two mutual orthogonal reflection patterns are visible in the same area of the printed optical effect layer. They result from the superimposed magnetic fields in the different magnetic arrangements according to the invention.

The security element is created by a setup of magnetic fields. Various assemblies of such devices for aligning a magnetic printing ink with superimposed magnetic fields in a printing process are described in the invention. Methods for producing the optical effect layer according to the invention by printing on a continuous web or by sheet-fed printing with the superimposition of magnetic fields are listed in the dependent claims, as are data carriers for producing security and value documents with such a security element.

It is also an object of the invention to find a method of magnetic orientation that can be used for small-scale designs. The alignment method according to the invention should be able to be used in a continuous printing process at high production speeds. This process can be a sheet fed printing process, a semi-continuous rotative printing or a rotative printing process. The invention is intended to make it possible to freely select a geometric shape and thus to realize an individual design in a security feature formed therewith. The possibility of copying by using a large-scale feature of analogous optical appearance accessible to a wider public thus will not be possible.

According to a first aspect, the invention relates to orienting magnetically orientable pigments in an ink with at least two superimposed magnetic fields. The first magnetic field creates a magnetically induced alignment in an ink which results in an optical effect with a main optical active axis. Tilting of the hardened ink on a carrier in the direction parallel to this main optical active axis will result in a visible change of reflection intensity. The main optical active axis of a magnetic field is directly linked to a mechanical axis of the assembly of magnets creating the magnetic field.

A well-known example from security printing of an alignment pattern of magnetically orientable pigments in an ink having only one main optical active axis is the so-called flip-flop effect. In terms of this invention, flip-flop describes the switch of high intense reflection in an area to low intense reflection in the same area with changing the angle of observation of the area by tilting the printed element parallel to the direction of the main optical active axis.

Another known representative of such a magnetic field with an alignment pattern of magnetically orientable pigments in an ink having only one main optical active axis is the so-called rolling-bar effect. This describes an arrangement of non-spherical, magnetically oriented pigments in an ink in a pattern that produces a stripe of high reflective intensity. If the aligned ink printed on a substrate is tilted in the direction of the main optically active axis of the OEL, the high reflectance stripe will move parallel or anti-parallel to this main optical active axis. Tilting in a direction perpendicular to this main axis does not cause any optically clearly visible change in the reflection intensity at the surface of the OEL.

The device comprises at least one second magnetic field creating an alignment pattern of the magnetically orientable pigments in the ink yielding an optical reflection with one main optical active axis that is perpendicular to the main optical active axis of the first magnetic field. Perpendicular in this context is defined to lie in the range of 85° < α < 95°, α describing the angle between the main optical active axes of the two superimposed magnetic fields. The second magnet assembly used may have further main optical active axes as well as an overall magnetic structure showing a 3-dimensional optical reflection effect. This 3-dimensional reflection may also include a visible dynamic effect. Dynamic effect in this context describes the movement of a reflection intensity between two edges in the magnetic pattern which accompanies the tilting of the hardened ink on a carrier.

The optical reflection resulting from the second magnetic field pattern shows at least an effect by tilting along an axis perpendicular to the main optical active axis of the first magnetic field and optionally may further be recognized by observing from different directions, including the direction of the main optical active axis of the first magnetic field.

According to the invention the magnetically orientable pigments in the ink are aligned by the superimposition of at least two magnetic fields as described before. The pigments’ alignment structures of both magnetic fields are interlaced in the same area, showing both optical reflection effects after hardening of the ink. For non-spherical, magnetically orientable pigments aligned with such interlaced patterns, the visible reflection has at least two main optical active axes aligned perpendicular to each other. Tilting in direction of main optical active axis 1 will show the optical reflection from magnetic field 1, e.g. a flip-flop effect or a rolling-bar effect, whereas tilting in direction of main optical active axis 2 will show the optical reflection from magnetic field 2, e.g. a dynamic 3-dimensional effect. Moreover, reflection effects from magnetic field 2 may be visible from different directions of observation, e.g. a 3-dimensional pattern visible from any direction.

The assembly of the magnetic fields for the superimposition itself can be designed in one or more parts. Various components of the device can be provided contiguous or in principle in the same place or far away from each other. The device itself can be provided separately or in combination with other devices such as a printing press. The alignment of magnetically orientable pigments in an ink with superimposed magnetic fields according to the invention uses at least two separate magnetic fields. More assemblies of magnets can be connected in series to create further superimposition effects.

The term ink is to be interpreted as broadly as possible for the purposes of the invention. Essentially, it is a sufficiently fluid coating material that can be used in printing processes. The ink comprises a binder system which may be colorless and transparent or colored in the visible spectrum. At least one type of magnetically orientable pigment is incorporated, which is often grey-glossy but can also have a colored or color-changing surface coating. In addition to the magnetically orientable pigments, coloring pigments can be mixed into the ink, preferably pigments that are themselves translucent and emit colors due to a certain external stimulus, e.g. UV radiation, or appear colored due to light interference against the grey-glossy background of the magnetically orientable pigments. Due to this structure of the ink, the additional pigments in the ink can show an optical effect in addition to the reflection effects resulting from the alignment of the magnetically orientable pigments with the device and the process according to the invention.

There is a great freedom of choice regarding the material of magnetically orientable pigments. Due to the manufacturing process, magnetically orientable pigments are not perfectly spherical. A plurality of non-spherical magnetically orientable pigments is already sufficient for the implementation of the present invention in the ink. A special coating of the magnetically orientable pigments is not necessary for alignment with the device of the present invention. But of course, specially coated pigments can also be used. The magnetically orientable pigments preferably belong to the substance class of ferromagnetic pigments such as cobalt, nickel, samarium, iron, the oxides of the substances mentioned and other representatives of this substance class. In principle ferrimagnetic pigments can be used as well.

There are some requirements regarding the magnetic properties of the magnetically orientable pigments in the ink to be aligned by the device according to the invention. Preferably, the pigments should be magnetized with small magnetic forces, i.e. the pigments are of a magnetic material that has a low coercive field strength. The coercivity K of the magnetic pigments should lie in the range of 10 Oe < K < 500 Oe, preferably between 20 Oe < K < 300 Oe.

There are further requirements regarding the geometry of the magnetizable pigments to be used in the ink for the process. The plurality of the pigments should be non-spherical, preferably have the shape of a platelet. A platelet has two flat sides bearing a good reflection of light illuminating the flat side. It is possible to define two perpendicular main axes x and y of the pigment in the plane of its flat surface (compare to Fig. 1). The size of the pigments should not be too small in order to yield a good reflection by the platelet-shaped pigments oriented in the ink by the magnetic field patterns of the device described in this invention. The mean size (D50) of the pigments should lie between 14 µm < D50 < 50 µm, preferably between 17 µm < D50 < 30 µm. The (D50) value may be accompanied by a (D90) value between 21 µm < D90 < 80 µm, preferably 25 µm < D90 < 60 µm. From a technical point of view, smaller pigments can be used as well, but they will reduce the optical clarity of the effect.

The invention uses magnetic field patterns to be superimposed with magnetic fields. The use of the term pattern implies a certain basic complexity of the generated magnetic field. In particular, a simple magnetization of a magnetic plate or of a permanent magnetic bar such that the entire upper side of the plate or the bar represents a north pole and the bottom side represents a south pole or vice versa is not considered a magnetic field pattern. In any case, there are at least two North poles and two South poles realized within a magnetic plate or within a setup of dipole magnets or there is a rotationally symmetrical magnetic pattern created with a rotating dipole magnet bar or an array of rotating dipole magnets.

The size of the magnetically orientable pigments is essential due to the alignment in the ink with the superimposed magnetic field pattern according to the invention. Only a part of all magnetically orientable pigments is aligned by the first magnetic field of the device. The rest of the magnetically orientable pigments is aligned or realigned by the second magnetic field pattern superimposed to the first magnetic field in the device in the process. This establishes an integration of two optical effects by superimposing the two magnetic alignments of the magnetically orientable pigments in an ink without completely destroying the alignment of the other magnetic field involved in the superimposition. Both magnetic alignments are interleaved to each other. They are to be seen in the coating side by side, i.e. they appear in the same area of the aligned printed coating.

According to the invention, at least two magnetic fields or at least one magnetic field and at least one magnetic field pattern are superimposed to form an overall pattern. Exposed to this superimposition of fields, the ink containing the magnetically orientable pigments is aligned with the overall magnetic pattern. The magnetic fields of the magnet assemblies act simultaneously or consecutively on the magnetically orientable pigments in the ink to be aligned. It is almost obvious that the superimposition of relatively simple magnetic fields results in a relatively complex overall magnetic field pattern. Magnetic field lines are always closed loops, various complex geometries or generic patterns result from the superimposition according to which the magnetically orientable pigments are aligned in the ink.

According to the invention, at least two magnetic fields or at least one magnetic field and at least one magnetic field pattern are superimposed on each other to align the liquid ink over the entire printing area of the ink. In this area, after alignment there are no clusters of pigments aligned nearly parallel to each other, as is the case with alignment using only one magnetic field, which results in a magnetic structure with only one main optical active axis, such as the alignment pattern of a standard flip-flop effect or a rolling-bar effect. According to the invention, the pigments aligned with the magnetic field lines of the first magnetic field are embedded between the pigments aligned with the second magnetic field pattern. The two alignment structures obviously differ from each other, otherwise the two orthogonal main optical active axes of the two superimposed magnetic fields or magnetic field patterns could not be seen separately from each other. Both alignment structures are continuously interleaved with each other, the plurality of adjacent aligned pigments are not nearly parallel to each other.

The magnetically orientable pigments have to be large enough in order to optically sum up their reflection with observation in direction parallel to the two main optical active axes of the two superimposed magnetic fields or magnetic field pattern. The reflection pattern has to be visible even if the pigments aligned according to the associated magnetic field structure are spaced apart by some pigments aligned by the second magnetic field pattern. The second visible structure resulting from the alignment of pigments by the second magnetic field pattern is embedded in the reflection of the first magnetic field. It can be directly seen by choosing a perpendicular direction of observation, in which a main optical active axis of the second magnetic field pattern will show its associated reflection structure. Moreover, reflection from the alignment of the second magnetic field pattern can also be seen with viewing in direction of the main optical active axis of the first magnetic field, if the second magnetic field pattern is of the type of a dynamic 3-dimensional pattern.

According to another embodiment of the invention, further alignment patterns can be achieved in that a third alignment pattern is written into a first generated orientation pattern with interlaced magnetic fields with a serial arrangement of further assemblies of magnets. This results in the possibility of achieving overall patterns in the ink which cannot be achieved with the single arrangement of a superimposition of a first magnetic field and a second magnetic pattern.

According to a preferred embodiment of the invention, at least two magnetic fields or one magnetic field and one magnetic field pattern for the superimposition are arranged on different sides with respect to the substrate carrying the ink with the magnetically orientable pigments. The position of the two magnetic fields must be fixed to each other so that the generated magnetic field pattern is not blurred during the alignment process. It is possible, for example, to attach the device of the second magnetic field pattern below the substrate in direct contact to the substrate and the first magnetic field with a suitable distance to the substrate above the substrate, the side, where the ink is printed on. The distance of the first magnetic field to the substrate can be varied to achieve the optical alignment that best matches the desired appearance of the aligned pattern. This distance depends on the magnetically orientable pigments used in the ink as well as on the magnet assemblies used and has to be tested individually for each production setup.

According to an alternative embodiment of the invention, it is also possible for the two magnetic fields to be mounted on the same side of the substrate. It is achieved that the magnetically orientable pigments are successively aligned in the magnetic fields of both magnetic fields.

According to a preferred embodiment of the invention, the first magnetic field is created by a magnetic-blade (44). Within the framework of this invention a magnetic-blade is an arrangement of two solid state hard-magnetic dipoles. Hard magnetic materials in the context of this invention are from the class of materials of magnetized CoSm, NdFeB, AlNiCo, CuNiFe, CuNiCo, FeCoCr or other hard magnetic materials. The identical poles (N-N or S-S) of the two dipole magnet bars face each other and are attached to each other with mechanical contact. The dimension of the two dipoles are identical (Length: 10 mm < l < 200 mm, preferably 30 mm < l < 130 mm. height: 10 mm < l < 200 mm, preferably 30 mm < l < 130 mm. Thickness: 2 mm < d < 25 mm, preferably 4 mm < d < 15 mm). The magnetic force of the magnet bars used in the magnetic blade can be defined by the weight, which can be carried with the magnets. In the device of the invention a load capacity of 0,1 kg < lc < 10 kg, preferably 0,5 kg < lc < 4 kg is sufficient.

The magnetic field lines of the two dipoles in this setup cannot mix (see Fig. 2b)). They bend away the field lines of the facing magnetic dipole and thus at the outside of the two magnets the field lines are directed to the left and to the right with respect to the contact-plane of the two magnets. The magnetic field lines below the magnetic-blade (44) are pointing upwards to the left and to the right with regard to the physical center-axis of the blade (see Figs. 2b and 5a)). Magnetically orientable pigments in an ink align parallel to these field lines, when they come near enough to be moved by the magnetic field forces. In reflection from the surface of the platelet-shaped pigments, one bright area left from the contact axis is visible. With the same viewing angle, the area on the right side of the contact axis has no reflection and appears dark. Change of the angle of viewing via tilting will shift the reflection, the dark area becomes bright, the bright area turns dark. The main optical active axis of the magnetic-blade is perpendicular to the contact-plane of the two magnets. Rotating the magnetic-blade by 90° rotates the main optical axis by 90°.

According to a further preferred embodiment of the invention, the first magnetic field is created by an electro-magnet. The electro-magnet is connected to an electrical power station supplying a direct current. The power supply is adjusted so that the load capacity lc of the electro-magnet lies between 0,1 kg < lc < 10 kg, preferably 0,5 kg < lc < 4 kg. The magnetic field lines of the electro-magnet (43) have two main directions left and right to the mechanical center-axis of the electro-magnet (see Fig. 2c)). Magnetically orientable pigments in an ink align parallel to these field lines, when they come near enough to be moved by the magnetic field forces. In reflection from the surface of the platelet-shaped pigments, one bright area left from the contact axis is visible. With the same observation angle, the area on the right side of the contact axis does not reflect and appears dark. Shifting the angle of viewing via tilting will switch the reflection, the dark area becomes bright, the bright area turns dark. The main optical active axis of the magnetic-blade is perpendicular to the mechanical axis of the electro-magnet.

According to another preferred embodiment of the invention, the first magnetic field is created by a hard-magnetic cylinder. The cylinder’s diameter is 2 mm < d < 30 mm, preferably 5 mm < l < 15 mm, the length is 1mm < l < 20 mm, preferably 5 mm < l < 15 mm. The load capacity lc of the cylinder-magnet lies between 0,1 kg < lc < 5 kg, preferably 0,2 kg < < lc < 2 kg. The cylinder-magnet is magnetized in direction of the cylinder axis, its parallel planes define the N- and the S-pole. The rotational symmetric magnetic field lines (symmetry-axis is the center-axis of the cylinder-magnet) align the magnetically orientable pigments in the ink in two alignment directions (see Fig 5 b)), left and right to the central axis of the cylinder-magnet. The alignment takes place as long as the distance of the cylinder-magnet above or below the coating is smaller than the range of its magnetic forces to move the magnetically orientable pigments in the coating. The mechanical center-axis of the cylinder magnet is directed perpendicular to the main optical active axis of the alignment pattern. To achieve this result, the cylinder has to be pulled over the entire length of the ink layer (11). It is possible as well to keep the cylinder magnet (47) fixed and transport the substrate (14) beneath it. The center-axis of the cylinder (47) should cover the center-axis of the ink layer (11) and should be held parallel during the relative movement of the substrate beneath the cylinder. The resulting optical reflection from the magnetically oriented pigments in the ink shifts between high and low reflection intensity in the two areas above and beneath the center axis of the ink layer (11). This is seen with tilting the substrate upwards and downwards. The main optical active axis resulting from the alignment with the cylinder-magnet is perpendicular to the center-axis of the cylinder magnet (47). Changing the direction of the relative movement of the cylinder-magnet changes the direction of the main optical active axis induced to the ink coating.

According to another preferred embodiment of the invention, the first magnetic field is created by an arrangement of two hard-magnetic cylinders. Both cylinders’ diameters lie between 2 mm < d < 30 mm, preferably between 5 mm < l < 15 mm, the length is 1mm < l < 20 mm, preferably 5 mm < l < 15 mm. The load capacity lc lies between 0,1 kg < lc < 5 kg, preferably 0,2 kg < lc < 2 kg. The two cylinder-magnets (47) are magnetized in direction of their cylinder axis. They are mounted in direct contact of their N-poles or their S-poles. Like with the magnetic-blade, the resulting magnetic field lines are bend away from the other magnet. This cylinder magnetic-blade creates the alignment of the magnetically orientable pigments in the ink. with a relative movement of the cylinder magnets over the wet printed ink. The contact-plane of the two magnets (47) has to be directed parallel above the center-line of the ink layer (11). Either the cylinder magnetic-blade or the substrate has to be pulled with the contact plane and the axis of the printed field kept parallel. The magnetic field of the cylinder magnetic-blade aligns magnetically orientable pigments in an ink with a pattern as indicated in the cross-sectional scheme of Fig. 5c). The reflection from this alignment curvature shows a stripe of high reflection intensity. This results from the specular reflection of pigments aligned parallel to the surface of the ink layer. With tilting, the specular reflection moves along the curvature of the aligned pigments in direction parallel to the tilting direction, the rolling-bar effect. The effect is visible in the direction perpendicular to the contact plane of the two cylinder-magnets of the cylinder magnetic-blade. This defines the main optical active axis of this magnet assembly.

According to a preferred embodiment of the invention, the second magnetic pattern creates a dynamic 3-dimensional effect. In the context of this invention a dynamic 3-dimensional effect has a visible depth in the reflected image and shows a continuous movement of the reflection intensity maximum in the 3-dimensional structure with changing the angle of observation by tilting the aligned coating. The intensity maximum always moves from one edge of the magnetic field pattern to the next edge. The edges are defined by the magnetic field lines of the magnetic pattern. They are positioned at the points, where S- and N-pole of two magnetizations meet. Neighboring magnetic structures with the same geometrical setup will simultaneously show the same reflection intensity shift. This shift may be seen in at least one direction, the main optical active axis of the field pattern. Most likely, 3-dimensional magnetic patterns are symmetrically repeating their structure in more than one direction. In this case, there is more than one main optical active axis.

The recordings in Figs. 3 and 4 explain such dynamic 3-dimensional patterns in an OEL. Fig. 3 is an example of a diamond pattern with almost square diamonds associated to the alignment structure of the magnetically oriented pigments in an ink. There is a periodicity of the structuring pattern within the surface, i.e. in both dimensions of the visible surface of the recordings. Zig-zag stripes extend in the x and the y-direction crossing each other in a periodic distance. Areas of high and low reflection intensities alternate in x- and y-direction, with a maximum at the intersection points. The magnetic field of the magnetic plate (21) causes the geometric positioning of the pigments in the ink coating in relation to the surface of the coating. At the transition point N-S, the alignment of the pigment plane is parallel to the surface of the ink yielding specular reflection. Between the transition edges, the intensity of the ink reflection decreases. Tilting the sample in direction of one of the two main optical active axes – i.e. the connecting lines between the intersection points - will lead to a movement of the reflection maximum from the intersection point to the center of the diamonds. And further on in direction of the next intersection point. Simultaneously, the reflected light in the center of the diamond emerges from a deeper layer in the ink body than the reflection at the edges. Overall, the structure appears as a continuous dynamic 3-dimensional reflection pattern of light by the alignment of the magnetically orientable pigments in the ink. It becomes best seen with tilting the samples from left to right or from up to down. These are the two main optical active axes of the pattern described.

The optical appearance results from the alignment structure of the magnetically oriented pigments in the ink. It is a continuous alignment of the magnetically orientable pigments in the ink along a curve (see Figs. 3 and 4) defined by the magnetic field lines of the magnetic plate (21). Due to the highest specular reflection in the intersection points the optical pattern has the same periodicity and the same spacing b as the magnetic stripes in the magnetic plate (21).

By tilting the ink on the support carrier the reflection intensity maximum moves along the continuous curved alignment of the magnetically oriented pigments in the ink. The parts distant from the transition edges N to S of the magnetic stripes become bright. With a tilting angle of nearly 90 degrees, the pigments in the center between the stripes are reflecting. The curved alignment of the magnetically oriented pigments creates a continuous dynamic movement of the reflection maximum which is accompanied with a 3-dimensional effect, since with increasing tilting angles pigments sited further below the surface of the ink are illuminated and reflect. Overall the pattern shows a dynamic 3-dimensional appearance with real depth to an observer and cannot be copied in this form.

A dynamic 3-dimensional alignment of magnetically orientable pigments is as well created by the use of two magnetic plates adhered on top of each other. Using two such plates increases the freedom of design possibilities very much. Fig. 4 explains the effect of such an assembly with an arrangement of mutual orthogonal linear polarized plates (22) and (23). The recording shows the optical result of alignment of magnetically orientable pigments in an ink by an assembly of plates (22) and (23), where the fields at the surface of the assembly have different magnetic strengths and contribute different to the entire magnetic field of the assembly. Variation of plate thickness d and/or of magnetic force F of the plates (22) and (23) yields different reflection structures as desired.

Obviously, as visible in Fig. 4b), again there is a periodicity of the structuring pattern within the surface, i.e. in both dimensions of the visible surface of the recordings. Wavy stripes extend in the y-direction, the left front of which is planar and the right front of which is wavy. Areas of high and low reflection intensity alternate in the x-direction, and bright stripes with intensity maxima are additionally offset from one another, so that a wave crest follows a wave trough and again a wave crest. Overall, the structure creates a continuous dynamic 3-dimensional reflection of light by the aligned magnetically oriented pigments in the ink. This becomes best seen with tilting the samples from left to right or from up to down. This demonstrates the two main optical active axes of the magnetic plate assembly of this example. The optical appearance results from the alignment structure of the magnetically oriented pigments in the ink. It is a continuous alignment of the magnetically orientable pigments in the ink along a curve defined by the magnetic field lines of the two magnetic plates.

According to a preferred embodiment of the invention, the setup for the dynamic 3-dimensional alignment consists of elastomer magnetic plates. These magnetic plates are built of an elastomer matrix in which ferrites are embedded. They are often called magnetic rubber plates or tapes. The adhesive forces F_adhesion of the plates lie in the range of 5 g/m² < F_adhesion < 500 g/m², preferably in the range of 20 g/m² < F_adhesion < 200 g/m². Surprisingly, this is already sufficient for achieving good overall alignments of magnetically orientable pigments in an ink. The thickness d of the plates lies preferably in the range of 0.1 mm < d < 5 mm, particularly preferably in the range of 0.3 mm < d < 3 mm. This plate thickness is easy to produce, and with the appropriate choice of material, it is flexible and therefore easy to handle.

According to a preferred embodiment of the invention, the magnetic plates are flexible. This has the advantage that the plates can be integrated into an existing printing process or into a printing press in a variety of ways. For example, it is possible to adhere the plates on a cylindrical carrier or to clamp them on it. A corresponding flexibility allows the mounting of prefabricated plates after appropriate dimensioning on cylindrical carrier rollers of different diameters.

According to a preferred embodiment of the invention, a magnetic plate has a polymer-bonded magnetic material. In this way, it is commercially possible to improve the shaping of magnetic materials through plasticization, thus making shaping more flexible overall and streamlining the production of series quantities. For example, polymer-bonded hard ferrite and NdFeB magnets nowadays are manufactured in large quantities on special injection molding machines.

According to another preferred embodiment of the invention, the elastic magnetic plates are linear magnetized. The ferrites are magnetized linearly in the plane of the plate in a special process according to the desired geometrical specification. The orientation of the magnetization can range from parallel N-S lines or N-S adjacent to S-N lines to curved arrangements of such bands to individual dash- or even dot-shaped arrangements of a single band. The latter design variations also allow to form a composite character or logo, which is formed exactly from a continuous line in the shape of the character or logo. The 3-dimensional appearance of the security feature is selectively adjusted by the design of the magnetization of the ferrites in the elastic magnetic plate or in a combination of plates. It is possible to display a structure as desired.

According to a preferred embodiment of the invention, at least one of the magnetic field patterns of a magnetic plate has a periodicity. In this context, periodicity means the regular repetition of a magnetic field characteristic along a specific direction, e.g. the main optical active axis. Relevant directions here are those given by the substrate or the magnetic plate body or the associated surface. When two magnetic field patterns are superimposed, each with a periodicity in different directions, an overall magnetic field pattern with a periodicity in two different dimensions or directions within the plane of the magnetic plates results. This structure is characterized by visible edges resulting from N-S intersection lines or intersection points. The connecting lines of these edges define the main optical active axes of the magnetic alignment structure.

According to a preferred embodiment of the invention, at least one of the magnetic plates has stripe-shaped magnetization with polarization in the plane of the plate body. This results in a correspondingly stripe-shaped magnetic field pattern. Preferably the individual stripes are continuous, i.e. they form or cover the entire plate panel along their main axes. The individual stripes can have the same width or different widths. In the simplest case, the stripes are actually straight or linear, but they can also be z. B. jagged or wavy. Linear stripes are preferred because of their ease of manufacture. A width b of the stripes that is relevant from an application point of view lies in the range from 0.5 mm < b < 30 mm, preferably in the range between 5 mm < b < 10 mm. Opposite magnetic poles of adjacent stripes meet forming a N-S transition point at the edge between the two stripes. The main optical active axes of the magnetic plate are defined by the transition lines and the connecting lines between transition lines.

According to a preferred embodiment of the invention, at least two magnetic plates are used for creating the dynamical 3-dimensional magnetic pattern. Two linear elastomer magnetized magnetic plates are adhered on top of each other. The typical thickness d of the plates lies in the range from 0.05 mm < d < 5 mm, preferably in the range from 0.3 mm < d < 3 mm. Typical magnetic adhesive forces F_adhesion of the plates lie in the range of 5 g/m² < F_adhesion < 500 g/m², preferably in the range of 20 g/m² < F_adhesion < 200 g/m². The upper plate has less magnetic force than the lower plate. This is easily achieved by two linear magnetized plates with a thickness ratio R from upper : lower plate of (1:1,2) < R < (1:4), preferably (1:1.5) < R < (1:3). The axis of the linear magnetized bands of the upper plate is rotated with respect to the axis of the linear bands of the bottom plate. According to a preferred embodiment of the invention, the polarizations of two plates are oriented differently from one another, in particular rotated through 45°, 90° or 120° with respect to one another. In particular, when the polarization is oriented in the plane of the magnetic plate body, regular two-dimensional patterns of the magnetic field lines of the superimposition of the two magnetic plates can be generated very easily, the pattern of which can then be found again in the alignment pattern of the magnetically oriented pigments in the ink. It is possible that, apart from the orientation of the magnetic plates, at least two of the plates are otherwise essentially identical. The periodical alignment structure is characterized by visible edges resulting from N-S intersection lines or intersection points. The connecting lines of these edges define the main optical active axes of the magnetic alignment structure. Such an assembly obviously has at least two main optical active axes. Its direction in an aligned ink is directly determined by the angular direction of the magnetic plate assembly with regard to the printed layer of the ink.

According to a preferred embodiment of the invention the 3-dimensional magnetic pattern is individualized. An individual magnetic alignment pattern aligns the magnetizable pigment in an ink in geometry of signs, letters or defined structures. Via the special magnetic field pattern of the magnetic setup in the device a desired object is represented in the alignment of the pigments in the ink.

According to a preferred embodiment of the invention the individual magnetic alignment is established by magnetic elastomer plates. The use of elastomers instead of a polymer as a binder leads to the production of rubbery, elastic magnets. These can be produced either by extrusion or by calandering. Corresponding products exist in a large variety in the market and can be purchased commercially for a device according to the invention. Elastomer plates are magnetized in geometries representing letters, signs or other geometrical structures. These magnetization forms maybe magnetized N-S or S-N perpendicular to the plane of the elastic magnetic plate. Different structures can be placed on the magnetic plate next to each other or so that they overlap each other. The different magnetic structures may have different magnetic forces and different direction of magnetic poles N-S or S-N with respect to the surface of the plate. By this variability, the overall pattern is easily individualized and will show an easy to see dynamic 3-dimensional structure representing the desired object.

According to a preferred embodiment of the invention, the elastomer magnetic plate to create the dynamic 3-dimensional effect is adhered on a cylindrical carrier. This can be a deflection roller, which can be integrated in a particularly simple manner into a rotary printing process. In this case the back side of the substrate preferably comes into direct contact with one of the plates on the cylindrical carrier. The size of this contact area can be described by a wrap angle α. The size of this angle of wrap α can be chosen very flexibly and, in particular, can also be easily adapted to a desired process speed. However, it has been shown that in most cases wrap angles α in the range 1° < α < 90°, preferably 3° < α < 40°, most preferably 5° < α < 20° are perfectly adequate to achieve a good alignment effect even with high production speed. This is because the alignment of the magnetically orientable pigments in the ink is very fast and usually takes only tenths of a second. Attaching the plates to a cylindrical carrier has an advantage: After alignment, it is important not to blur the alignment pattern produced in the ink when removing the substrate with the ink from the magnetic plates. The use of a cylindrical support allows the substrate to be lifted off tangentially from the cylindrical support at the end of the wrap, and the alignment pattern created in the ink is not smeared with this geometry.

According to another preferred embodiment of the invention the dynamic 3-dimensional magnetic field pattern is created by a rotating hard-magnetic setup of dipole magnetic cylinders mounted on a platform. The platform is attached to the axis of an electrical motor. The motor rotates the magnets with a rotational speed adjusted so that during the process of alignment there will be N rotations. The number of rotations N lies between 0.5 < N < 10, preferably 1 < N < 5. The rotating magnetic setup has dimensions of length l between 2 mm < l < 30 mm, preferably between 5 mm < l < 20 mm. It is also preferred to use a magnetic setup with the length similar to the length of the area of the printed ink, so that a geometrical registration on the complete printed area is possible.

According to a preferred embodiment of the invention the rotating magnetic setup consists of a cylinder-magnet. The diameter of the magnetic cylinder D lies within 0,1*L < D < 1.0*L, preferably 0.5* L < D < 0.8*L. L is defined by the larger length on the printed ink layer. The strength of the magnetic cylinder should have a load capacity lc of 0.2 kg < lc < 15 kg, preferably 0.5 kg < lc <5 kg. The cylinder-magnet is attached to the axis of the electric motor in the center of the dipole magnet with the plane face (equals to the N- or the S-pole of the magnet) opposing the substrate with the wet ink coating. The rotating cylinder-magnet creates a rotational symmetric alignment of magnetic orientable pigments in the ink in shape of a funnel (see Fig. 6a)) yielding a dynamic 3-dimensional appearance in reflection. The reflection from this specific pattern obviously is rotational-symmetric. From all directions one can see the main optical active axis.

According to another preferred embodiment of the invention the rotating magnetic setup consists of a dipole magnetic bar. The hard-magnetic dipole maybe a cylinder with diameter d between 1 mm < d < 15 mm, preferably 2 mm < d < 10 mm or a bar with side length s depending on the printing length L of the ink layer to be oriented. The strength of the magnetic bar should have a load capacity lc of 0.2 kg < lc < 15 kg, preferably 0.5 kg < F < 5 kg. The dipole bar is attached to the axis of the electric motor in the center of the dipole magnet. The result of the rotating magnetic field is an alignment of the magnetically orientable pigments in shape of a lens (see Fig. 6b)) yielding a dynamic 3-dimensional appearance in reflection. This reflection pattern is characterized by a rotating main optical active axis. The resulting optical reflection is seen from every viewing direction.

According to another embodiment of the invention the rotating magnetic setup is individualized. By engraving the surface of the magnetic dipole bar with signs, e.g. stars, the resulting magnetic alignment from a rotating engraved dipole bar is changed. The engraved signs alter the magnetic pattern in the alignment of the printed coating. Looking at it one can see a trace of the engraved mark like a comet tail. This allows to select a geometric shaping as desired, making it possible to implement a customized design in a security feature formed therewith. The possibility of copying it by using a large-scale feature of analogous optical appearance accessible to a wider public is made impossible by the customized design.

According to another preferred embodiment of the invention the second magnet assembly in the superimposition uses magnetic plates to induce a dynamic 3-dimensional effect with at least one main optical active axis perpendicular to the axis from the alignment of magnetically orientable pigments with the first magnetic field comprised in the superimposition (see Fig. 7). The edges of the assembly (20) are placed parallel to the edges of the ink layer (11). Then the main optical active axes of the plate assembly (20) are parallel to the ink layer, too. One of the two main optical active axes is perpendicular to the main optical active axis of the alignment resulting from the assembly (43).

All the assemblies of magnets described above have at least one main optical active axis directly linked to a mechanical axis of the assembly and can be used as source for magnetic fields to be superimposed according to the invention, so that the superimposition results in a field pattern yielding reflection from aligned pigments which has two mutual orthogonal main optical active axes. The direction of the main optical active axis associated with each magnet assembly used in the device (100) can be easily adjusted by positioning its mechanical center-axis parallel or perpendicular to the transport direction of the substrate (14). For the five assemblies described exemplary in Fig. 3 to Fig 5. 15 possible combinations in the device (100) result. Fig. 6 and Fig. 7 exemplary show four of these combinations as to explain the superimposition of the magnetic fields and the result from it. All combinations use the electro-magnet (43) as source of the first magnetic field comprised in the superimposition of fields. Without any technical restriction, at this position a magnetic-blade (44), a cylinder magnetic-blade (47) or a cylinder-magnet (47) can be used as well.

According to a preferred embodiment of the invention, the device (100) for the superimposition comprises an electro-magnet and a rotating cylinder-magnet (63), its plane facing the substrate (14) with the wet ink (11), see Fig. 6a). The electro-magnet (43) induces a magnetic alignment of the magnetically orientable pigments in the ink with into two main directions parted by the center-line of the electro-magnet (43) (see Fig. 5c)) adjusted parallel above the center-line of the ink layer (11). Simultaneously, the rotating cylinder magnet assembly (60) creates a rotational symmetric alignment of magnetic orientable pigments in the ink in shape of a funnel. In the ink (11), both alignment structures will be nested within each other. Since the amount of magnetic orientable pigments does not change, the number of pigments aligned by each of the two structures will not be as large as it would be for an alignment with a single magnetic field. The result of the overlapping magnetic fields is a mixture of both alignment structures as indicated in the schematic cross-sectional Z view in Fig. 6a). On the one hand, there are enough pigments oriented in one direction to yield a high and low reflection intensity with tilting as known from the flip-flop effect, on the other hand in the same cross-section there are pigments magnetically oriented along the surface of the magnetic funnel associated to the magnetic pattern of the rotating cylinder magnet (63). In a cross-section Z, this funnel yields a curve, parallel to which the magnetically orientable pigments align. With a magnetic cylinder of diameter d < L (length of the printed ink layer) the magnetic field lines align the pigments in a curve that yields reflection maxima under perpendicular observation of the substrate plane (14) at the edges of the ink layer (11). The intensity reduces to the center of the ink layer (11), where there is no specular reflection from the pigments to be seen. Rotation of the substrate (14) around axis E moves the intensity maximum in direction of the center of the ink layer (11). Here, the pigments below the surface of the ink layer reflect the incident light. The rotating magnetic cylinder (63) induces a dynamic 3-dimensional effect. This effect is interleaved with the flip-flop effect induced by the electro-magnet (43). Tilting of the ink layer (11) from left to right along the main optical active axis of the rotating cylinder’s alignment shows the dynamic 3-dimensional movement of the reflection intensity maximum in the bright area yielding from the flip-flop alignment. Tilting the ink layer (11) upwards or downwards along the main optical active axis of the electro-magnet’s alignment shifts the bright area to the other part of the ink layer above or beneath the center line. Now the dynamic effect can be observed in this second part of the printed layer (11). This is possible, because the magnetically orientable pigments are not aligned nearly parallel as with the standard flip-flop effect, but adjacent pigments are aligned alternating by the upper (43) and the lower (60) magnet assembly of the setup in Fig. 6a).

Another preferred device (100) for the superimposition according to the invention consists of an electro-magnet (43) and a rotating dipole magnet (64), see Fig. 6b). The rotating permanent magnetic bar (64) has a length l with 0,5*L < l < 1.5*L, preferably 0.8*L < l < 1,2*L. L is defined by the larger length on the printed ink layer (11). The magnetic bar is mounted below the substrate (14) with its main mechanical axes parallel to the plane of the substrate. The rotating magnetic bar (64) creates an alignment of the magnetically orientable pigments parallel to the surface of a concave lens. In the cross-section shown schematically in Fig. 6b), this yields an elliptical curve. The pigments lie parallel to the surface of the ink layer (11) in the region of the center-line of the ink layer. To the edges of the ink layer (11), the oriented pigments are aligned with a downwards slope in to the layer (11). The associated reflection intensity is highest with perpendicular observation in the center of the ink layer (11). With tilting (equivalent to rotation around the axis E, arrows indicate the tilting directions in Fig. 6b)) the intensity maximum will move along the curve to the edges of the printed layer (11). This dynamic 3-dimensional movement effect is superimposed to the flip-flop effect created by the electro-magnet (43). It is visible either in the upper or lower part of the ink layer (11), depending on the rotation around axis D. The main optical active axes of the two interlaced alignment structures are directed perpendicular to each other.

The assembly sketched in Fig. 6b) is another example for the effect of the interlaced magnetic alignment. Moreover, there are other combinations of assemblies of magnets yielding an interlaced alignment of magnetically orientable pigments using rotating permanent magnets. According to this invention, they have to create the two alignments in the same area of the ink layer (11) as shown in the schematic cross-sectional views. With other setups, the curve describing the alignment of the pigments creating the dynamic 3-dimenisonal structure will differ. The characteristic of the resulting reflection intensity around the axis E will therefore be different.

A further preferred device (100) for the superimposition of magnetic fields according to the invention comprises a magnetic plate (21) for the creation of a dynamic 3-dimensional alignment effect. The alignment of the magnetically orientable pigments in ink (11) by the superimposition of both magnetic fields is schematically shown in the cross-sectional Z view in Fig. 7a). In the example shown the reflection intensity has two maxima with perpendicular observation of the ink layer (11). Rotation around axis E moves the maximum to three locations, two at the edges, one in the center of the ink layer (11). This periodicity is valid for l = L = 3*b. (b is the width of one magnetic stripe in plate (21), l is the length of the printed ink layer). The magnetic plate (21) induces a dynamic 3-dimensional reflection effect. For the eye, the reflection from the pigments with a slope with regard to the surface of the ink layer 11 emerges from beneath the surface, yielding a 3-dimensional effect. The superimposition of the two magnetic fields yields an interlaced alignment of the magnetically oriented pigments in the ink layer (11) which results in a light reflection structure shown in the schematic pictures of Fig. 7a) The reflection pattern of plate (21) is superimposed to the flip-flop reflection due to the alignment of the electro-magnet (43). It is seen both in rotation around axis E and D. The representation in Fig. 7a) shows a perpendicular projection of the rotation onto substrate (14), rotation around axis D transfers to tilting upwards and downwards, rotation around axis E tilting from left to right. These two directions are parallel to the two mutual orthogonal main optical active axes of the two magnet assemblies superimposing their magnetic field lines.

A further preferred device (100) for the superimposition of magnetic fields according to the invention comprises a first set of two magnetic plates (22) and (23) for the creation of a 3-dimensioanl dynamic alignment effect, see Fig. 7b). The optical result of the alignment with such an assembly (20) of magnetic plates is described in Fig. 4. It has one main optical active axis parallel to the white dotted center-line of the ink layer (11). The alignment pattern of the magnetically oriented pigments is shown in the schematic pictures in Fig. 7b). It is not identical to the pattern shown in Fig. 7a). The reason for the change of the induced reflection pattern is the different curve to which the magnetically orientable pigments are tangentially aligned, as shown in Fig. 7b). Here the structure is influenced by the different magnetic forces of the two involved magnetic plates (22) and (23), which do not contribute identical magnetic forces at the surface of the assembly 20. The periodicity of this magnetic pattern is in turn transferred to the reflective structure of the ink layer (11) and the two main optical active axes of the two superimposed magnetic fields again are perpendicular to each other.

According to a further preferred embodiment of the invention both the first and the second superimposing assemblies of magnets have magnetic field lines yielding a reflection structure from magnetically oriented pigments that has only one main optical active axis. The axes of the first and second magnetic fields are arranged perpendicular to each other in such an arrangement of the magnet assemblies. The magnet assemblies of the first and the second alignment device can be of the same type, i.e. an assembly creating a shift between high and low reflection intensity in one area with changing the angle of observation – i.e. the flip-flop effect – or an assembly creating a stripe of high reflection intensity moving with changing the direction of observation – i.e. the rolling-bar effect. They can also be composed of different types, i.e. a superimposition of a rolling-bar and a flip-flop effect perpendicular to it. As with the other preferred embodiments of the invention, the superimposition yields an interlaced alignment of the magnetically orientable pigments in the ink. They are not nearly parallel anymore, but the main axes of the plane of platelet-shape adjacent pigments aligned by magnetic field 1 and aligned by magnetic field 2 are directed perpendicular to each other. The optical reflection effects of the two magnetic fields are observed when viewed in the direction of the main optical active axes of the two alignment structures.

In order to enable industrial production of the security features, the assemblies according to the invention for orienting magnetically orientable particles in an ink are integrated into a printing process or into a printing machine, so that continuous production is possible.

According to a preferred embodiment of the invention, the process for orienting magnetically orientable particles comprises one drying unit, with the help of which the alignment of the magnetically oriented pigments in the ink is fixed. The drying unit can be arranged so that drying already starts when the magnetically orientable pigments are still in the effective area of the alignment assembly. However, it is also possible for the drying unit to be located at a distance from the superimposed alignment assembly, so that the drying process starts after the alignment of the magnetically orientable pigments has been completed and a substrate with the OEL that is still wet has been transported to the drying unit. Alignment unit and drying unit can work either simultaneously or in series and can also be arranged accordingly in the device according to the invention. The drying unit can work in different ways, e.g. B. thermal, microwave-induced, via IR radiation, electron beam curing, UV curing, etc.. The drying unit preferably works on the basis of UV radiation curing.

According to another embodiment of the invention, the process for orienting magnetically orientable particles comprises more than one drying unit, with the aid of which the orientation of the magnetically oriented pigments can be fixed in the ink. Surplus drying units may be fixed in a position, where they can partially fix the ink before alignment or partially fix the already partially aligned ink, which has passed one magnet assembly of the device. The magnetically orientable pigments in the ink are still mobile and are eventually aligned by the second or by further magnet assemblies following in series to create the overall superimposed magnetic orientation patterns. This intermediate curing can work either simultaneously or in series with the previous alignment of the pigments in the ink. After the final alignment in the last magnet assembly the ink will be finally hardened in the last drying unit. Hardening can be done either simultaneously or after the last alignment step. Overall, radiation-curing inks that dry as a so-called 100% system are preferred. When using inks from which solvents or water must be removed in the drying unit, this substance migration causes turbulence, which reduces the alignment of the magnetically orientable pigments and can destroy the optical clarity of the reflection of the aligned pigments. Therefore, the use of such inks should preferably be combined with simultaneous drying and alignment. Radiation-curing inks have an overall advantage over thermally drying inks and should therefore preferably be used with the device according to the invention.

According to a preferred embodiment of the invention, the substrate with the ink layer comes to rest on the aligning assembly during the process of aligning the magnetically orientable pigments in the ink, or the assembly can be moved at the speed of the substrate. A relative speed between alignment device and substrate must be prevented in order not to blur the orientation pattern in the ink. A relative speed between alignment device and substrate must be prevented in order not to blur the orientation pattern in the ink.

Another preferred printing process according to the invention uses a setup of magnetic plates adhered to a deflection roller in a printing machine in the device (100), see Fig. 15. Only one exemplary alignment device for each of the two magnetic fields (40) and (70) is shown in Fig. 15, but of course one or more further aligning devices (40) and (70) of the same or different type can also be provided in a process flow in a web-fed printing press. After printing of ink (11) the substrate (14) is transported to the first alignment assembly (40). The alignment of the magnetically orientable pigments results in a reflection pattern with a first main optical active axis. Thereafter, the substrate (14) is further transported to the device (70) to induce a second alignment pattern with a main optical active axis perpendicular to the axis resulting from the alignment in station (40). Assembly (70) consists of magnetic plate assembly (20) located on a deflection roller (71). Two magnetic plates (22) and (23) are used, which are adhered onto the roller (71). Other types of attachment, for example by means of clamping, are also possible. It is also possible to use a single magnetic plate (21) on the roller (71) as well. In the area of a wrap angle α, the rear side of the substrate web (14) comes into direct contact with the deflection roller (71). The deflection roller rotates at a speed that is adapted to the transport speed of the substrate web (14) so that there is no relative movement between the two during the contact of the substrate web (14) with the deflection roller (41). During the contact time, the magnetically orientable pigments in the ink layer (11) are aligned with the superimposed magnetic field lines of assembly (70). The ink (11) may be cured simultaneously with the alignment of the magnetically orientable pigments with a curing unit (50) above the unit (70). Curing of the ink may also be run after substrate (14) has been transported off the deflection roller (71) or at other positions C in Fig. 15. After the orientation and curing process, the substrate web (14) with the dried magnetically oriented ink is transported further via a further deflection roller (72). The sequence of the described alignment process can be rotated, likewise simultaneous alignment on the deflection roller with attached magnetic plates is possible according to the described procedure.

According to a further aspect of the invention, this relates to a printing machine with a device for orienting magnetically orientable pigments in an ink. The device is designed as described in more detail with the figures. At least the magnet assemblies for creating magnetic fields and patterns to be superimposed according to claim 1 of this invention - relating to the superimposition of magnetic fields and magnetic patterns for orienting magnetically orientable particles in an ink - must be implemented into the printing machine. Additional feature implementations are optional. There are no special requirements for the printing machine itself; it can be any standard type of printing machine. The device according to the invention for orienting magnetically orientable pigments in an ink can be used very universally.

According to a further aspect of the invention, this relates to a printing process, in particular a rotary printing process on a roll or sheet, in which magnetically orientable pigments in an ink are oriented using a device as generally described above. Thus, what is new and inventive about the claimed printing process lies in the step of alignment, in which the magnetically orientable pigments in the ink are aligned with superimposed magnetic fields and patterns resulting in a reflection pattern with two mutual perpendicular main optical active axes. The direction of these two axes can be easily determined by the mechanical positioning of the magnetic fields comprised in the device according to the invention.

According to a preferred embodiment of the invention, the alignment of the magnetically orientable pigments in the ink is performed sequentially in at least two separate alignment steps. The device for aligning the pigments with the superimposed magnetic pattern consists of at least two magnet assemblies for aligning the pigments with respect to the reflection effect with the first main optical active axis and with respect to the second reflection effect with at least one main optical active axis which is perpendicular to the first main axis. The first magnet assembly aligns the magnetically orientable pigments and the second magnet assembly completes the alignment by superimposing the second alignment in the ink. Either the magnetic-blade, the magnetic cylinder-blade for rolling-bar effect or a magnetic pattern for a dynamic 3-dimensional alignment can be used in the first alignment step followed by the remaining second magnet assembly. The two magnetic alignment steps can be completely separate or partially overlap. Further alignment steps in the process are also possible.

According to another preferred embodiment of the invention, the superimposed alignment of the magnetically orientable pigments in the ink is performed simultaneously in one alignment step. The device according to the invention comprises two magnet assemblies for aligning the pigments with respect to the main optical active axis of the first assembly and with respect to the second main optical active axis aligned perpendicularly thereto. The first and second magnet assemblies superimpose their fields, resulting in an interlaced alignment of the magnetically orientable pigments.

According to a preferred embodiment of the printing method according to the invention, the magnetically orientable ink is applied using the screen-printing technology. In this case, a radiation curing process is preferably used to cure the magnetically orientable ink. The screen-printing process has the advantage that the necessary layer thickness of the ink can be generated very easily. The typical layer thickness d lies between 1 μm < d < 40 μm, preferably between 5 μm < d < 20 μm.

According to another preferred embodiment of the printing method according to the invention, the magnetically orientable ink is applied using the flexographic printing technology. In this case, a radiation curing process is preferably used to cure the magnetically orientable ink. The flexographic printing process has the advantage that design variations of the printing design may be established without high costs. The necessary layer thickness of the ink can be generated with using suitable gravure cylinders for the coloring of the printing plate. Anilox cylinders with a line density d_l between 20 l/cm < d_l < 160 l/ cm, preferably 40 l/cm < d_l < 120 l/ cm are recommended.

In a preferred embodiment of the printing method, the printing method registers the magnetic orientation to the printing area of the ink on a substrate with the aid of fiducial marks generated in the magnetic alignment. With such a registration it is possible for example to position the magnetic pattern for the dynamic 3-dimensional effect in the ink within the printed contour of a company logo.

According to a further preferred embodiment of the printing method according to the invention, at least one further printed security feature is applied on the substrate above or below the OEL, resulting in a combined security effect. In principle, the type of additional printed security feature can be freely selected; it can be, for example, a thermochromic ink or an UV-fluorescent ink or a microprint.

According to a further preferred embodiment of the printing process according to the invention, in addition to the magnetically orientable pigments, non-magnetically orientable special pigments are also added to the ink in order to achieve a combined security effect. These non-magnetically orientable pigments can be selected for example from the group of color effect pigments (“color shift” ink), thermochromic pigments or UV-fluorescent pigments.

According to the invention, the OEL can be individualized by combination with an unaligned ink (15) which is the identical ink as used for printing the aligned ink layer (11), see Fig 8a). The two inks (11) and (15) are identical. Ink (15) is not aligned by a magnetic field before being hardened and is printed directly onto the ink (11), which is aligned according to the invention. The visibility of the design printed with ink (15) depends on the viewing direction of the whole OEL. Maximum reflection intensity from the flip-flop structure in the interlaced alignment in ink layer (11) outshines the printed structure of ink (15). Rotation of the element around axis D shifts the reflection intensity from high to low, the design print of ink (15) becomes visible. Due to the overlapping alignment structure from the dynamic 3-dimensional effect in ink layer (11) according to the invention the effect is not perfect, but still it is clearly visible for the naked eye.

According to another preferred embodiment of the invention the OEL is combined with an unaligned ink (16), which is not identical with ink (11), see Fig 8b). Ink (16) is a resin filled with color pigments, preferably dark color pigments, e.g. black pigments. Ink (16) represents a design of a letter, of a logo or of other signs. Ink (16) is covered by the ink layer (11) which is aligned according to the invention. If there is a reflection maximum in the layer (11) above the ink layer (16), the pattern of the ink (16) is optically obscured and cannot be seen with the naked eye. Rotation of the ink layer (11) around axis D shifts the reflection maximum to a reflection minimum, the design of ink (16) becomes visible as a printed design beneath ink layer (11). The overlapping magnetic fields in ink layer (11) reduce the effect a bit, but it is still very visible.

Both ways to integrate an unaligned printed design lead to a further possibility of individualization of the security feature according to the invention They can be executed with the method shown in Fig 8 a) or 8b) solely or with a combination of both as shown in Fig 8c). This is a further preferred embodiment of the invention.

According to a further aspect of the invention, this relates to a data carrier which has been produced in particular using the printing method and device described in the invention. During printing, the ink layer (11) was treated with an assembly of superimposed magnetic fields according to the invention for orienting magnetically orientable pigments and the pigments located therein were aligned accordingly. The element (11) bears a corresponding frozen pattern resulting in a visible superimposed magnetic alignment with two perpendicular main optical active axes. The OEL is printed full coverage on the area printed with ink (11). The data carrier (11) is also equipped with an additional security element (12), for example a hologram stripe applied with heat and pressure. In the exemplary embodiment shown in Fig. 9a), the print of the ink layer (11) can be printed directly onto the substrate (14) or onto a previously printed primer (18) (respective alternative, see Fig. 9b) with the primer filling out any unevenness in the substrate surface. The primer may also include a further security feature, e.g. a UV fluorescent ink. Fig. 9c) shows a cross-section plane Z through the data carrier (10) in Fig. 9b). The primer (18) lying beneath the ink layer (11) is clearly visible. It goes without saying that a previous printing of the substrate (14) with a primer layer (18) can also be used in all other embodiment variants according to the invention, even if this is not specifically stated in the examples described.

The data carrier is essentially 2-dimensional, so that the two mentioned dimensions of the data carrier span an area. The first main optical active axis of the OEL in the superimposed reflection pattern of the magnetically oriented ink layer preferably runs along mutual orthogonal directions with respect to the edges of the data carrier, but other angles of this first main axis are also conceivable. Due to the nature of the OEL, the second main optical active axis preferably is parallel to the second edge of the data carrier, but may of course have another direction as well.

According to the invention, in another preferred embodiment of the data carrier, a further security element (17), see Figs 10 to 12, is printed on top of or beneath the OEL (11). In Fig. 10b) to Fig. 12b) a cross-section plane Z through the data carrier (10) is shown in order to further explain the construction. The additional security element (17) can be, for example, a thermochromic ink that is opaque at room temperature and becomes transparent above the activation temperature. Due to the overprinting with the security element (17), the underlying magnetically oriented layer (11) is only visible above the activation temperature of the thermochromic ink. With this selection of the overprint situation, design combinations can be achieved that ensure the recognition and thus also the protection of a document of value or a product. This increases the protection of data carrier (10) against counterfeit attacks.

In a preferred embodiment of the invention a security element (17) lying on top at least completely covers the magnetically oriented ink layer (11) or covers it at the edges. The layer (17) has, for example, a gap in the form of a letter. The recess can be in the form of numbers, letters or geometric shapes such as company logos. If a thermochromic color is selected for the security element (17), the OEL (11) can only be seen in the recess or over the entire surface, depending on the temperature applied to data carrier (10).

The exemplary embodiments according to the invention describing the combination of the OEL (11) with another security element (17) were explained using a thermochromic ink as an additional security element (17). Other security features can be used instead of or in addition to the thermochromic color. For example, UV-fluorescent pigments, IR-reactive substances, anti-Stokes inks etc. can also increase counterfeit security in overlapping and undercutting geometries, as well as a combination with characteristic substances that can only be proven forensically. Examples include DNA markers, optical micro-taggants and others.

According to a further embodiment of the invention, the OEL (11) attached to the data carrier (10) is printed with a gap, e.g. using a letter or another sign. This variant makes it possible to see elements beneath the security element (11) on the data carrier (10). Examples of such elements are microprinting or fluorescent printing directly on the data carrier (10). This combination of security features also results in an overall increase in the counterfeit security of the data carrier (10).

According to a further embodiment of the invention in addition to printing further security features above or below the OEL, non-magnetically orientable special pigments are incorporated directly into the magnetically orientable ink. For example, it is interesting to add color-changing pigments to the magnetically orientable color, which themselves do not show any reaction to magnetic fields because this increases the recognizability of a security element in different viewing directions of the OEL.

According to another preferred embodiment of the invention the data carrier with the attached OEL has at least one of the security features listed below: hologram film, color shift effect, guilloche printing, intaglio printing, printing of polarization effects, micro-intaglio printing, UV fluorescence, fiber incorporation, security thread, watermark. The combination of different security features yields a further increased security of the data carrier according to the invention. A data carrier equipped with an OEL created according to the invention may carry further security features. For example, it may be a banknote with a watermark, fluorescent coloring fibers, security thread, transferred security foil, printing elements such as fluorescent inks or inks showing a color tilt or a polarization effect. The same applies to tickets, value documents, documents for identification and authorization, cash cards, security labels and comparable documents. Advantageously, the security element in the described embodiments is coupled directly with other security elements. This further extends the protection provided by the individually adapted combination of reflection patterns with two perpendicular main optical active axes and optional with a dynamic 3-dimensional alignment achieved by the embodiment according to the invention.

In further embodiments of the invention, direct integration of fluorescent or phosphorescent pigments, thermochromic pigments, IR-reactive pigments or pigments with an anti-stokes effect is provided. The respective pigments can be added individually or mixed to the magnetically orientable ink. It is advantageous to apply the additional effects separately on or under the magnetically orientable ink in a separate coating layer. In this case, the printing of the additional protective layers can be carried out overlapping, undercut or / and provided with a separate printing design. A data carrier according to the invention which is equipped with a combination of two or more security elements as described is of course significantly better protected against forgery and copying attacks.

The representations shown in the following figures are all sketches that are not exact either in terms of their dimensions or in terms of their perspective. Instead, they have only been used to explain the principle of the invention.

Fig. 1 shows a schematic representation of non-spherical magnetically orientable pigments. As an example, for two pigments the main axes of the plane of the pigments x and y as well as the surface normal z of the plane are indicated.

Fig. 2 shows alignment of magnetic pigments (indicated as oval plates with main axes x and y and surface normal z) in magnetic fields. The main axis x of non-spherical magnetically orientable pigments in an ink align parallel to the magnetic field lines. The magnetically orientable pigments, for example ferromagnetic pigments, orient themselves along the magnetic field lines and are concentrated according to the magnetic field strength gradients towards the areas of high field strengths. The shape of the magnetic field lines is always a closed loop. The curvature of the loop depends on the distance to the magnet and on the shape of the magnet. The shape of the magnets in Fig. 2a) to 2c) is a bar, the extension into the plane of the paper is only indicated in Fig. 2d), showing the principle extension of the magnetic bars in Fig. 2a) and 2b) as well as of the core of the electro-magnet in Fig. 2c).

Fig. 2a) Magnetic field lines of a permanent magnetic bar (dipole magnet) with a schematic view of the resulting alignment of magnetically orientable pigments in an ink printed on a carrier in cross-section plane Z. The two main directions of pigment alignment yielding an optical high and low intense reflection (bright – dark shift with tilting) are obvious.

Fig. 2b) Magnetic field lines of two permanent magnetic bars (dipole magnets) mounted with opposing poles and a schematic view in cross-section plane Z of the resulting alignment of magnetically orientable pigments in an ink printed on a carrier. The two main directions of alignment yielding an optical high and low intense reflection (bright – dark shift with tilting) are obvious. Reducing the distance between the magnetic bars will bend the magnetic field lines steeper, since the field lines are always closed and will not cross other field lines or melt together. A so-called magnetic-blade is created at the point of contact of the two magnetic rods.

Fig. 2c) Magnetic field lines of an electro–magnet. Also shown is the schematic view in cross-section plane Z of the resulting alignment of magnetically orientable pigments in an ink printed on a carrier. The two main directions of alignment yielding an optical high and low intense reflection (bright – dark shift with tilting) are obvious.

Fig. 3a) shows an example of a first magnetic plate that can be used as magnetic source for a magnetic pattern for superimposition according to the invention for orienting magnetically orientable pigments. The magnetic plate (21) consists of several crossing adjacent magnetic stripes of width a and b. Opposite magnetic poles meet (N - S - N - S - N - S) in both directions of the crossing stripes. The width b of the individual magnetic stripes typically ranges between 1 mm < b < 30 mm, preferably between 3 < b < 20 mm. The magnetic stripes can have the same width a and b or of different widths within the magnetic plate (21). The stripe widths a and b directly affect the magnetic orientation of the magnetically orientable pigments in the ink, and therefore are a parameter that can be used to influence the final pattern in the OEL.

Fig. 3 b) shows a recording of the reflection from the alignment pattern and a schematic view of the resulting pigment alignment in cross-section plane Z.

Fig. 4 illustrates, in a schematic representation, an embodiment of two magnetic plates (22) and (23) arranged one above the other. In the case shown, the magnetic stripes of the upper plate (23) are arranged perpendicular to the stripes of the lower plate (22). In the 90° arrangement shown in Fig 4a), the resulting magnetic field pattern results in a reflection structure shown in Fig. 4b) accompanied with the resulting pigment alignment in cross-section plane Z.

Fig 5 shows magnet assemblies yielding alignment patterns with one main optical active direction. This axis is perpendicular to the dotted white center-line of the ink layer (11) indicated in the figures. Tilting the ink (11) on the support (14) parallel to the direction of this main optical active axis shows the optical effect created by the magnet assembly’s field lines. In Figs. 5a) to 5c), this is a shifting reflection maximum in an area – i.e. the flip-flop effect, in Fig 5d) this is a moving intensity maximum stripe – i.e. the rolling-bar effect.

Fig. 5a) to 5c) show three different magnet assemblies to align magnetically orientable pigments in an ink (11) so that with respect to the centerline of the ink layer (11) on the substrate (14), pigments are nearly parallel to each other with two distinct directions left and right from the centerline. A schematic view of the resulting pigment orientation in a cross–section plane Z of the ink layer (11) is shown respectively in the figures 5a) to 5c).

Fig. 5a) shows the assembly of a magnetic-blade (44), a mechanical combination of two permanent magnetic blocks (45) and (46). The blocks are mounted in a way, that both N-poles of the two blocks are in direct contact. Rotation of the printed layer (11) around the axis D is shown schematically in Fig 5 a), where the rotation axis D is projected into the plane of the carrier (14) and the rotation changes to a tilting of the ink layer (11) on the substrate (14) upwards and downwards, as indicated with the arrows.

Fig. 5b) shows the use of a permanent cylinder-magnet (47) to create a flip-flop effect. The resulting alignment pattern is indicated in the schematic view of cross-section plane Z in Fig. 5b). The resulting optical reflection is seen with tilting the substrate upwards and downwards, as indicated with the arrows.

Fig. 5c) shows an electro-magnet (43) creating the alignment of the magnetically orientable pigments in the ink. The electro-magnet is shown as a sketch. It is built from a core block (48), which is wrapped by a copper wire coil (49). The wire is combined to an electrical power supply (not shown in the sketch) supplying a direct current. The core (48) extends the coil (49) at the upper and the lower end. With an applied electrical current, the N- and the S-pole emerge. The magnetic field of the electro–magnet (43) aligns magnetically orientable pigments in an ink as indicated in the cross-sectional scheme of Fig. 5c). The resulting optical reflection is seen with tilting the substrate upwards and downwards, as indicated with the arrows.

Fig 5d) shows an arrangement (41) of two cylindrical magnets (47) mounted with the same magnetic pole facing each other. The magnetic field of the cylinder magnetic-blade aligns magnetically orientable pigments in an ink with a pattern as indicated in schematic view of cross-section Z in Fig. 5c). The resulting optical reflection is seen with tilting the substrate upwards and downwards, as indicated with the arrows.

Fig. 6 shows a device (100) comprising two assemblies of magnets creating a reflection effect with a main optical active axis directed perpendicular to the white dotted center-line of the coated layer (11). The second magnetic setup in device (100) superimposing its magnetic field pattern results in a reflection pattern that has a main optical active axis parallel to the direction of the white dotted center-line of the ink layer (11). The two main optical active axes are perpendicular to each other. The two magnetic devices are mounted so that their two magnetic fields overlap in the plane of the ink layer (11) printed on substrate (14). The distance of the second assembly below the substrate can be adjusted with a pneumatic cylinder (65).

In both Fig. 6a) and Fig. 6b) an electro-magnet (43) is mounted above the substrate (14) parallel to the center-axis of the ink layer (11). The distance between the electro-magnet (43) and the substrate can be adjusted as desired.

Fig. 6a) shows a rotating magnet setup (60) below the substrate (14). This setup comprises an electro-motor (61), driving an axis (62) and a permanent cylinder-magnet (63) mounted on the motor axis (62). The speed of rotation and the distance between the rotating magnet assembly (60) and the substrate (14) can be adjusted as desired. The resulting alignment pattern of the magnetically orientable pigments is shown schematically in the cross-section in Fig. 6a). The resulting reflection pattern seen with tilting (indicated with arrows) the OEL is shown schematically.

Fig. 6 b) shows a further preferred assembly of superimposition of two magnetic fields according to the invention. A rotating permanent magnetic bar (64) is mounted below the substrate. The resulting superimposed alignment of the magnetically orientable pigments is shown schematically in the cross-section in Fig. 6b). The resulting reflection pattern seen with tilting (indicated with arrows) the OEL is shown schematically.

Fig. 7 shows an embodiment of device (100) using magnetic plate assemblies (20) to superimpose their magnetic field pattern with the magnetic field of an electro-magnet (43). The distance of assembly (20) with regard to the substrate (14) is adjusted with the pneumatic cylinder (65). It is possible to lift the assembly (20) to direct contact to the substrate (14). The edges of the assembly (20) are parallel to the ink (11).

Fig. 7a) shows a magnetic plate (21) mounted below the substrate (14). The plate (21) should have a dimension l equal or larger than the printing length L of the ink layer (11). With L = l it is possible to transfer the periodicity of the magnetic alignment induced by the plate (21) to the interlaced alignment over the length L of the ink layer (11). The resulting alignment pattern and the resulting reflection pattern seen with tilting the OEL (indicated with arrows) is shown schematically.

Fig. 7b) shows a set of two magnetic plates in assembly (20) comprised in the device (100). The resulting alignment pattern and the resulting reflection pattern seen with tilting the OEL (indicated with arrows) is shown schematically.

Fig 8 shows an example of the aligned ink layer (11) printed on the substrate (14) in combination with printing an unaligned ink showing the design of a letter, a company logo or any other sign.

Fig 8a) schematically shows the unaligned ink (15) printed on the aligned ink layer (11). Inks (11) and (15) are identical. The setup of the printed layers is shown in the schematic cross-sectional view of plane Z. Tilting of the feature (indicated with the arrows) yields the schematically shown effect.

Fig 8b) schematically shows an unaligned ink (16) printed on OEL (11). Ink (16) is not identical with ink (11). The setup of the printed layers is shown in the schematic cross-sectional view of plane Z. Tilting of the feature (indicated with the arrows) yields the schematically shown effect.

Fig 8c) schematically shows a combination of both setups from Fig 8a) and Fig 8b). Tilting of the feature (indicated with the arrows) yields the schematically shown effect.

Fig. 9) shows an example of a data carrier (10) with an OEL (11) attached thereto. The data carrier (11) is equipped with an additional security element (12). In the exemplary embodiment shown in Fig. 9a), the print of the ink layer (11) can be printed directly onto the substrate (14) or onto a previously printed primer (18) (respective alternative, Fig. 9b)). Fig. 9c) shows a cross-section plane Z through the data carrier (10) in Fig. 9b).

Figs. 10), 11) and 12) each show a data carrier (10) which is equipped with a combination of the OEL (11) and a further security element (17) printed on top of or beneath it. In Fig. 10b) to Fig. 12b) a cross-section plane Z through the data carrier (10) is shown.

Fig 10) shows an exemplary embodiment in which a security element (17) lying on top of the OEL (11) partly covers it.

Fig. 11) shows an exemplary embodiment in which a security element (17) lying on top at least completely covers the magnetically oriented ink layer (11) or covers it at the edges. The layer (17) has, for example, a gap in the form of a letter.

Fig. 12) shows an exemplary data carrier (10) with an OEL (11) printed with gaps. Below the OEL (11) is a layer containing a microprinting (indicated by the magnifying glass in Fig. 12a).

Figs. 13) to 15) show examples of the integration of devices (100) in a printing press or a printing process. Exemplary the assemblies in the devices (100) are positioned above and below the substrate (14) but can be positioned on the same side as well, except for the simultaneous alignment process shown in Fig. 13c), 14c) and 15c). In the schematic figures 13) to 15) the ink (11) is cured at the end of the process with curing unit (50). It is also possible to integrate further curing units (50) at the positions C indicated in Fig. 13 to Fig. 15. In all three figures ink (11) with magnetically orientable pigments is printed in the unit (30) from an ink tray (31) onto a substrate (14) by means of a cylinder (32).

Fig. 13 a) shows a first arrangement in which the substrate (14) is in sheet format or an endless roll. After the ink (11) has been printed onto the substrate (14), the latter is transported to a first alignment device (40). In the example shown, the alignment device (40) is facing the upper side of the ink layer (11) on the substrate (14). The ink (11) is oriented by the magnetic field lines of the alignment device (40). The substrate afterwards is transported to the second alignment device (20) and to the curing unit (50).

Fig. 13b) shows the setup of an equivalent printing process. The alignment devices (20) and (40) change their position. The magnet assembly (20) acts on the ink layer (11) first, followed by the superimposed alignment of the magnetically orientable pigments in the ink (11) with device (40). Finally, the substrate is transported to the curing unit (50).

Fig. 13c) shows the process with a simultaneous alignment of the magnetically orientable pigments with devices (20) and (40). The magnetic fields of both devices superimpose in the layer of ink (11) and the ink (11) is cured in unit (50).

Fig. 14 a) shows a printing machine in which the substrate (14) is in sheet format or an endless roll. After the ink (11) has been printed onto the substrate (14), the latter is transported to a first alignment device (40). The alignment device (40) is facing the upper side of the ink layer (11) on the substrate (14). The ink (11) is oriented by the magnetic field lines of the alignment device (40). The substrate now is transported to the second alignment device (60). The magnetic alignment here is induced by a rotating magnet bar (64) as an example, afterwards it is cured in unit (50).

Fig. 14b) shows the setup of an equivalent printing process. The alignment devices (40) and (60) change their position. The alignment device (60) first acts on the ink layer (11), followed by the superimposed alignment with device (40). Curing of the ink takes place in unit (50).

Fig. 14 c) shows the process with a simultaneous alignment with devices (60) and (40) The magnetic fields of both devices superimpose in the layer of ink (11). Afterwards, the substrate (14) is transported to the curing unit (50).

Fig. 15 shows an example of a process flow with an exemplary alignment device for each of the two magnet assemblies (40) and (70). In Fig 15a) the first alignment takes place in assembly (40). The second alignment is superimposed in assembly (70) consisting of magnetic plate assembly (20) located on a deflection roller (71). Finally the ink (11) is cured in unit (50) and transported further to the next deflection roller (72).

Fig. 15b) shows an embodiment in which the magnetic alignment devices (70) and (40) change their position in the process compared. The first alignment is operating in (70), the superimposition of the second alignment in (40).

Fig. 15c) shows an embodiment in which the magnetic alignment devices (40) and (70) superimpose their magnetic fields simultaneously in the ink (11).

Figs. 16 and 17 show black & white recordings of printed OEL according to the invention. Two examples visually show the effect of the magnetic alignment according to the invention.

The best embodiment of the invention is to use a rotary printing process on a web or sheet, where the ink is printed with a rotary screen printing or flexographic printing unit. The ink should be aligned with a superimposition of magnetic fields, with the magnetic field of a magnetic-blade or a cylindrical magnetic-blade superimposed on the magnetic field pattern of a rotating dipole magnetic bar or an arrangement of two magnetic plates. The choice of which of the listed arrangements to use is not influenced by technical or production issues, but only by the question of what visual appearance the printed OEL should have after production. It is best to align the ink in two steps, starting with the magnetic field, followed by the magnetic field pattern. The ink should be dried at the end of the process in a UV curing device.

The invention can be used for the industrial production of printed security elements. The visual appearance of examples of printed OEL according to the invention very catchy describes the effect of alignment patterns of magnetically oriented pigments in an ink with two main optical active axes perpendicular to each other. Photographic recordings shown in Figs. 16 and 17 are used for the description of the effect of the invention:

Fig. 16 shows black & white photographic recordings of two magnetic alignments of magnetically orientable pigments in an ink with two main optical active axes directed perpendicular to each other. Arrows in Fig. 16a) indicate the tilting directions to view the effects. The recordings (representing the exact printed dimensions of the OEL) exemplary show such a superimposition of a magnetic flip-flop alignment and a dynamic 3-dimensional alignment resulting from a rotating magnet bar as has been described with Fig. 6b). In the middle aisle of Fig. 16 a) in a viewing direction perpendicular onto the surface of the OEL the majority of the small printed OEL shows a high and a low intense reflection area above and below the horizontal center-line. Tilting upwards and downwards shifts the area with high intense reflection from one part of the OEL to the other. At the edges of the small OEL the reflection intensity decreases due to the superimposed magnetic field from the rotating magnetic bar. The two recordings on the left and the right of Fig. 16a) show the optical reflection along the second main optical active axis of the superimposed alignment structure. When tilting the ink layer to the left reflection is high intense only at the right edge of the OEL. Tilting the OEL from left to right shifts the dark part from left to right in the OEL. The high intense reflection resulting from the magnetically oriented pigments parallel to the ink’s surface (see Fig. 6b) now is visible at the left edge of the OEL.

Fig. 16b) shows the effect of shifting the reflection intensity minimum from the left edge of the OEL to the right edge of the OEL. In this recording, the OEL is combined with the lettering “PHARMA”, overprinted on the aligned ink layer. The lettering ink is identical with the ink used for the OEL, but it has not been aligned at all, as has been described with Fig 8a). With tilting the OEL parallel to the direction of the main optical active axis of one of the two magnetic fields in the superimposition of fields (i.e. the magnetic field pattern resulting from the rotating magnetic bar), the lettering remains bright all the time. It becomes almost invisible with the part of the OEL showing a reflection intensity maximum (central viewing) and good readable at the dark edges of the OEL (viewing tilted to the right and to the left).

Fig. 17 shows black & white photographic recordings of two further magnetic alignments of magnetically orientable pigments in an ink with two main optical active axes directed perpendicular to each other. The recordings (representing the exact printed dimensions) exemplary show such a superimposition of a magnetic flip-flop alignment and a dynamic 3-dimensional alignment resulting from an assembly of a magnetic plate as has been described with Fig. 7a). Arrows indicate tilting directions.

The recordings of Fig. 17a) show the switch of high intense and low intense reflection area in the OEL to be observed with tilting the OEL upwards and downwards. This is the first main optical active axis of the two superimposed magnetic fields according to the invention. The second main optical active axis is already visible in the two recordings as well. It is directed parallel to the line connecting the bright intersection points of the magnetic structure of the magnetic field pattern resulting from the assembly of two magnetic plates used in the superimposition of fields. With tilting the OEL from left to right along this direction the dynamic movement of the reflection intensity maximum between the intersection points becomes visible. Since this is a dynamic effect, a video is needed to record it.

Fig. 17b) shows a further combination of the OEL described with Fig. 17 a) with an overprint with an identical ink as used for the OEL. The overprint is not aligned and thus shows a constant reflection intensity. This reflection is outshined in the area of high reflection of the OEL. Here the lettering printed on top of the OEL is not or almost not visible. In the region of low reflectivity of the flip-flop effect in the OEL, the lettering is easily readable. With the recorded OEL the lettering says “OK” and “GENUINE”, depending on the direction of observation of the flip-flop alignment. The structure of the 3-dimensional alignment remains visible in both parts of the flip-flop effect.

Figs. 16 and 17 show examples, how embodiments of the invention use easily exchangeable magnet assemblies and may be individually designed. This results in a large number of possible combinations which allow the most diverse magnetic patterns to be aligned in one ink. A combination with the other possibilities of printing unaligned inks with design patterns opens a further possibility of implementing a customer- and product-related design and correspondingly individually equipped data carriers that are provided with a corresponding magnetically oriented security feature. At the same time, the highest protection level against counterfeiting of the data carrier is achieved by the superimposition of two magnetic fields aligning the magnetically orientable pigments in the OEL with two visible main optical active axes perpendicular to each other.

With the aid of the invention, it has become possible for the first time to produce a printed security element based on pigments in an ink magnetically oriented with superimposed magnetic fields, resulting in two clearly simultaneously visible and distinct optical reflection effects with main optical active axes perpendicular to each other. With the process and the assemblies according to the invention the OEL can be produced in a simple, inexpensive, fast and reproducible manner.

Claims

Optical effect layer characterized in that it contains an ink having magnetically aligned pigments dispersed in a transparent binder system, the alignment caused by a superimposition of at least two or more separate magnetic fields or magnetic field patterns in such a manner that each magnetic field or magnetic field pattern that contributes to the superimposition separately forms at least one main optical active axis in the superimposed alignment pattern in such a manner that at least two of these separately formed main optical active axes lie parallel to the surface of the optical effect layer and are directed perpendicular to each other.
Optical effect layer according to claim 1, characterized in that all magnetic fields that contribute to the superimposition cause only one optical active axis each in the alignment pattern of the magnetically orientable pigments in the ink.
Optical effect layer according to claim 1, characterized in that at least one magnetic field pattern that contributes to the superimposition causes only one main optical active axis in the alignment pattern of the magnetically orientable pigments in the ink.
Optical effect layer according to claim 1, characterized in that at least one magnetic field pattern that contributes to the superimposition causes at least two main optical active axes in the alignment pattern of the magnetically orientable pigments in the ink.
Optical effect layer according to claim 4, characterized in that at least one magnetic field pattern that contributes to the superimposition causes an alignment pattern of the magnetically orientable pigments in the ink with two mutual perpendicular main optical active axes.
Optical effect layer according to claim 5, characterized in that the magnetic field pattern of an assembly of one or more magnetic plates producing a dynamic 3-dimensional reflection characteristic causes two mutual perpendicular main optical active axes in the alignment pattern of the magnetically orientable pigments in the ink.
Optical effect layer according to claim 1, characterized in that at least one magnetic field that contributes to the superimposition causes an alignment pattern of the magnetically orientable pigments in the ink with a reflection characteristic that exhibits a high reflection intensity region which transitions to a low reflection intensity when the optical effect layer is tilted in a direction parallel to the main optical active axis of the alignment pattern.
Optical effect layer according to claim 7, characterized in that the magnetic field of a magnetic-blade causes the alignment pattern of the magnetically orientable pigments in the ink that has the reflection characteristic that exhibits a high reflection intensity region which transitions to a low reflection intensity when the optical effect layer is tilted in direction parallel to the main optical active axis of the alignment pattern.
Optical effect layer according to claim 7, characterized in that the magnetic field of an electro-magnet causes the alignment pattern of the magnetically orientable pigments in the ink that has the reflection characteristic that exhibits a high reflection intensity region which transitions to a low reflection intensity when the optical effect layer is tilted in direction parallel to the main optical active axis of the alignment pattern.
Optical effect layer according to claim 1, characterized in that at least one magnetic field that contributes to the superimposition causes an alignment pattern of the magnetically orientable pigments in the ink with a reflection characteristic that exhibits at least one stripe of high reflection intensity moving parallel or anti-parallel when the optical effect layer is tilted in a direction parallel to the main optical active axis of the alignment pattern.
Optical effect layer according to claim 10, characterized in that the magnetic field of a cylinder magnet-blade causes the alignment pattern of the magnetically orientable pigments in the ink that has the reflection characteristic that exhibits at least one stripe of high reflection intensity moving parallel or anti-parallel when the optical effect layer is tilted in direction parallel to the main optical active axis of the alignment pattern.
Optical effect layer according to claim 1, characterized in that at least one magnetic field pattern that contributes to the superimposition causes an alignment pattern of the magnetically orientable pigments in the ink that is rotationally symmetric with a main optical active axis that is visible from all directions.
Optical effect layer according to claim 12, characterized in that an array of at least one dipole magnet mounted on a rotating electric drive producing a reflection pattern exhibiting a dynamic 3-dimensional characteristic causes the rotationally symmetrical alignment pattern of the magnetically orientable pigments in the ink.
Device for aligning magnetically orientable pigments in an ink layer, characterized in that the device comprises:
i) at least two separate mechanically non-directly connected arrays of dipole magnets or of magnetic plates causing a superimposed pigment alignment in an ink with well-defined main optical active axes, and
ii) a variable spacing and directional adjustment of the magnetic arrays which adjusts the geometric alignment pattern of the magnetically orientable pigments in an ink in such a manner, that the associated reflectance pattern exhibits two mutually perpendicular main optical active axes parallel to the surface of the ink layer.
Device according to claim 14, characterized in that the distance between each of the built-in magnet assemblies that contribute to the superimposition and the substrate carrying the ink layer is adjusted by means of a pneumatic cylinder and the directional adjustment of the magnetic fields or magnetic field patterns contributing to the superimposition is effected by mounting the magnet assemblies with their main mechanical axis parallel or perpendicular to the transport direction of the substrate in the device.
Device according to claim 14, characterized in that the distance of each built-in rotating magnet assembly that contributes to the superimposition is adjusted with respect to the substrate carrying the ink layer by means of a pneumatic cylinder.
Device according to claim 14, wherein the built-in magnet assemblies that contribute to the superimposition are arranged sequentially and serially align the magnetically orientable pigments in the ink.
The device of claim 14, wherein the built-in magnetic assemblies contributing to the superposition are arranged facing each other with the substrate with the ink layer between them so that the superposition simultaneously aligns the magnetic pigments in the ink.
Printing machine comprising a device according to claim 14 for orienting magnetically orientable pigments in an ink.
Printing machine according to claim 19 with at least one drying unit with the aid of which the alignment of the magnetically aligned pigments in the ink layer can be fixed.
Printing machine according to claim 19 with more than one drying unit by means of which a pre-curing, a partial curing and a final curing of the ink layer in the printing process can be carried out.
Printing machine according to claim 19, characterized in that the alignment of the magnetically aligned pigments in the ink layer is fixed with UV radiation curing drying the ink.
Printing machine according to claim 19, characterized in that the printing substrate stops in the position of at least one of the magnet assemblies that contribute to the superimposition during the duration of the alignment process of the magnetically orientable pigments in the ink.
Printing machine according to claim 19, characterized in that in the position of at least one of the magnet assemblies that contribute to the superimposition during the duration of the alignment process of the magnetically orientable pigments in the ink, the magnet assemblies and the substrate are transported at the same speed.
Printing process, in particular a rotary printing process on a roll or sheet, in which magnetically orientable pigments in a printing ink are aligned according to claim 1.
Printing process according to claim 25, wherein the magnetically orientable ink is applied by screen printing.
Printing process according to claim 25, wherein the magnetically orientable ink is applied by flexographic printing.
Printing process according to claim 25, wherein at least one further printed security feature is applied on top of or below the optical effect layer, resulting in a combined security effect.
Printing process according to claim 25, wherein the printing ink contains magnetically non-orientable special pigments in addition to the magnetically orientable pigments to achieve a combined security effect.
A data carrier characterized in that it carries an optical effect layer according to claim 1.
A data carrier according to claim 30 characterized in that the optical effect layer is positioned with its two main optical active axes parallel to the two center axes or to the two edges of the data carrier.
A data carrier according to claim 30 characterized in that it carries at least one of the following additional security features: Hologram foil, color shift effect, guilloche printing, intaglio printing, micro printing, UV fluorescence, fiber incorporation, security thread, watermark, polarizing-effect printing.