Method for producing optically variable elements, and optically variable elements for producing a printing ink and / or a security feature

Abstract

The invention relates to a method for producing optically variable elements, comprising a pigment production step, in which a plurality of magnetic color pigments (8) are produced in such a way that they are of flat design, have an identical outer contour having a maximum lateral extent d and satisfy the following condition A: 0 < (pj / d)2 < 0.2, where pa is the standard deviation of the distribution of the maximum lateral extent d, and an encapsulation step, in which at least one magnetic color pigment (8) is in each case encapsulated in such a way that there are a plurality of capsules (5) having a solid shell (6) and a liquid core (7), in which the at least one magnetic color pigment (8) floats and is thus magnetically alignable.

Description

[0001] Process for producing optically variable elements as well as optically variable elements for producing a printing ink and / or a security feature

[0002] The present invention relates to a method for producing optically variable elements and to optically variable elements for producing a printing ink and / or a security feature.

[0003] The optically variable elements are used for design purposes, but also in and / or as an authenticity feature. Such an authenticity feature, also referred to as a security feature, can, for example, have a particular optical reproduction depending on the viewing angle. For example, a variable optical reproduction due to magnetic exposure is known. Previous optically variable elements known due to magnetic exposure comprise platelet-shaped, optically variable mica pigments encapsulated in a capsule with an enveloping liquid. When viewed from above without a magnetic field, a cloudy or non-uniform color impression is visible depending on the position of the platelet-shaped pigments in the capsule. When a magnetic field is applied, these platelets align themselves according to the magnetic field.

[0004] However, the achievable contrast is low because the capsules vary in size and are sometimes filled with many pigments. This can lead to light scattering and thus a reduced contrast. Furthermore, the pigments can block each other within the capsule, making it impossible to reproducibly achieve the desired orientation by applying an external magnetic field. It has also been found that many capsules in the printing ink contain no pigment at all, or the pigments contained in the capsule are immobile and therefore cannot contribute to the described effect. Furthermore, the manufactured capsules vary greatly in diameter, meaning that very large capsules could potentially clog the screen printing screen used to apply the ink, and small capsules could no longer contribute to the movement effect and contrast.Finally, the print layer exhibits numerous defects, which further leads to low contrast. This can be caused, for example, by clogged screen openings in screen printing due to capsules that are too large.

[0005] Proceeding from this, it is therefore an object of the invention to provide an improved method for producing optically variable elements and improved optically variable elements for producing a printing ink and / or a security element.

[0006] The invention is defined in the independent claims. Advantageous further developments are specified in the dependent claims.

[0007] The method according to the invention for producing optically variable elements can comprise the following steps: a pigment production step in which a plurality of magnetic color pigments are produced such that they are flat (or plate-shaped), have a same outer contour with a maximum lateral extent d and satisfy the following condition A: 0 < (pa / d) 2 < 0.2, where pa is the standard deviation of the distribution of the maximum lateral extent d, and an encapsulation step in which at least one magnetic color pigment is encapsulated in such a way that a plurality of capsules with a solid shell and a liquid core in which the at least one magnetic color pigment floats and is thus magnetically alignable are present.

[0008] An essential point of the solution according to the invention is to produce the magnetic color pigments with a well-defined outer contour and the described low scatter of the maximum extension d.

[0009] This can be achieved, for example, by using a laser to write 3D structures into a photoresist and then vapor-depositing color-shift interference layers. This allows, for example, hexagonal pigments with a diameter of approximately 25 μm to be produced.

[0010] In the encapsulation step, one to a maximum of five magnetic color pigments can be encapsulated in each capsule.

[0011] The capsules can be manufactured in the encapsulation step such that the shell of the capsules has an outer diameter D and the following condition B is met: 0 < (po / D) 2 < 0.3, where po is the standard deviation of the distribution of the outer diameter D.

[0012] In the pigment production step, the magnetic color pigments can be coated with an optically variable thin-film system. The pigment production step and the encapsulation step can be carried out such that the following condition C is met: 1 < D' / d < 2.0, where D' is the inner diameter of the capsule.

[0013] The magnetic color pigments can be produced in the pigment production step with a thickness of greater than or equal to 0.5 gm and less than or equal to 4 gm and a maximum lateral dimension d of greater than or equal to 0.5 gm and less than or equal to 50 gm.

[0014] The magnetic color pigments can be produced in the pigment production step with a monodisperse pigment size distribution, whereby a single mean value for the maximum lateral extent d satisfying condition A is available for all magnetic color pigments.

[0015] The magnetic color pigments can be produced in the pigment production step with a bi- or tri-modal pigment size distribution, in which two or three mean values ​​for the maximum lateral extent d satisfying condition A are available for the magnetic color pigments.

[0016] If a bi- or tri-modal pigment size distribution is present, one or two mean values ​​of the distribution can be removed by one or more filtration steps or other separation processes, so that a bi- or monomodal pigment size distribution is then present.

[0017] The encapsulation step may comprise a sub-step of dispersing the magnetic color pigments in a core liquid and a sub-step of encapsulating the magnetic color pigments dispersed in the core liquid. The magnetic color pigments and the solid shell may be manufactured to repel each other.

[0018] Furthermore, optically variable elements for producing a printing ink and / or a security feature are provided, wherein the optically variable elements each comprise a capsule with a solid shell and a liquid core, wherein in each capsule at least one magnetic color pigment floats in the liquid core and is thus magnetically alignable, wherein the magnetic color pigments are flat, have a same outer contour with a maximum lateral extent d and are manufactured such that the following condition A is met:

[0019] 0 < (pa / d) 2 < 0.2, where pa is the standard deviation of the distribution of the maximum lateral extension d.

[0020] One capsule can contain one to a maximum of five magnetic color pigments. Preferably, each capsule contains fewer than four or three magnetic color pigments, and particularly preferably, each capsule contains exactly one magnetic color pigment.

[0021] The capsules may be manufactured in such a way that the shell of the capsules has an outer diameter D and the following condition B is met:

[0022] 0 < (pD / D) 2 < 0.3, where po is the standard deviation of the distribution of the outer diameter D.

[0023] The capsules are preferably spherical.

[0024] The magnetic color pigments can comprise an optically variable thin-film system. The optically variable elements can be designed such that the following condition C is met: 1 < D' / d < 2.0, where D' is the inner diameter of the capsule.

[0025] The magnetic color pigments can have a thickness of greater than or equal to 0.5 μm and less than or equal to 4 gm and a maximum lateral dimension d of greater than or equal to 0.5 gm and less than or equal to 50 gm.

[0026] The magnetic color pigments may further comprise features disclosed in connection with the inventive method for producing optically variable elements (including further developments thereof). Likewise, the inventive method for producing optically variable elements may comprise further process steps that are described in connection with the magnetic color pigments or are necessary to produce further features of the magnetic color pigments (including further developments thereof).

[0027] Furthermore, a security feature (or security element) is provided for arrangement on a value element, in particular a value document, wherein the security feature comprises a plurality of the optically variable elements.

[0028] A security feature can be understood, for example, as a printing ink comprising a plurality of optically variable elements. Furthermore, the security feature can be formed, for example, as a transfer element or as a film or window with a film cover on the value element. Furthermore, a data carrier, in particular a chip card, identification document, and / or value document (e.g., a banknote), is provided with a security feature comprising a plurality of optically variable elements.

[0029] In particular, the following properties of the magnetic color pigments are possible. They can be designed as magnetic interference pigments. Preferably, they can also feature the following details: o Use of magnetic interference pigments that offer high color contrast and high brilliance / intensity. o In principle, all known color shift structures are conceivable. o Symmetrical pigment structure:

[0030] Absorber - Dielectric - Reflector - Magnetic layer - Reflector - Dielectric - Absorber or

[0031] Absorber - Dielectric - Magnetic Reflector - Dielectric - Absorber or

[0032] Magnetic absorber - Dielectric - Magnetic reflector - Dielectric - Magnetic absorber o Additional nano structures can be transferred to the pigment by embossing the separating layer (especially when using water-soluble UV varnish or hot stamping varnish), resulting in additional color effects.

[0033] If the magnetic color pigments are provided with a ColorShift structure or an optically variable thin-film system and thus contain ColorShift pigments, the liquid core (or capsule liquid) can be colored in a shift color of the ColorShift pigments. The shift color is, in particular, a color that can be generated by the ColorShift pigments. Furthermore, additionally or alternatively, the solid shell of the capsule can be colored in a shift color of the ColorShift pigments. If both the liquid core and the solid shell of the capsule are colored in a shift color of the ColorShift pigments, these can be different colors or the same color.

[0034] The magnetic color pigments can be formed, for example, as magnetic aluminum pigments. They then preferably have a silvery-white or silver color. The liquid core (or capsule liquid) and / or the solid shell of the capsule are then preferably colored with a different color than the magnetic aluminum pigments. If both the liquid core and the solid shell of the capsule are colored, they can be the same color or different colors.

[0035] The magnetic pigments advantageously have a precisely defined outer contour. This can be round (e.g., circular, oval, etc.), polygonal (e.g., triangular, square, pentagonal, hexagonal, heptagonal, octagonal, etc.), or star-shaped (e.g., with 4, 5, 6, 7, 8, or more points). The outer contour is preferably square and particularly preferably hexagonal.

[0036] To produce the magnetic pigments, water-soluble or water-swellable UV embossing varnish / hot stamping varnish and various embossed structures, such as plateaus or bars, as well as wash ink for removing the pigments, are possible. The maximum lateral dimension d of the magnetic pigments can be understood, for example, as the diameter of the smallest circle that completely encloses the outer contour of the magnetic pigment. Therefore, the maximum lateral dimension d is also referred to below as the pigment diameter d.

[0037] The outer contour may be selected so that the following condition is met: 10 |im <= d <= 50 gm; preferably 15 gim <= d <= 40 gim; particularly preferably 20 |im <= d <= 30 m.

[0038] The magnetic pigments can be produced in such a way that a monodisperse pigment size distribution or a very narrow distribution curve is present. A monodisperse pigment size distribution is understood here in particular to mean that all magnetic pigments produced have the same outer contour and, if possible, the same pigment diameter.

[0039] The pigment size distribution can be characterized using a PDI (polydispersity index), with PDI = (oa / d) 2 , where oa is the standard deviation of the pigment diameter distribution:

[0040] 0 <= PDI < 0.2; preferred 0 <= PDI < 0.01; particularly preferred 0 <= PDI < 0.003

[0041] The pigment size distribution exhibits two or three average pigment diameters with the above size distribution (bi- or trimodal distribution). This can be achieved, for example, by mixing well-defined pigments. The magnetic pigments are preferably produced to have a defined pigment thickness of 0.5 gm to 4 gm, preferably 0.7 gm to 3 gm, particularly preferably 0.8 gm to 2 gm.

[0042] The following additional process steps or characteristics can be specified for pigment coating:

[0043] Coating with silane or phosphonic acid derivatives is possible using wet chemical processes.

[0044] The silanes can be described by the general molecular formula SLXR1R2R3. Where X is an alkyl radical with hydrophobic properties and R1, R2, and R3 are organic or inorganic radicals. The alkyl radical X consists of 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms. The radicals R1, R2, and R3 can be different or the same. If they are inorganic, they are hydrogen (H) or chlorine (Cl). If they are organic, they are alkoxy radicals consisting of 1 <= m <= 4 carbon atoms.

[0045] The silanes can be described by the general molecular formula SiXYRiR2. Where X and Y are alkyl radicals with hydrophobic properties and Ri and R2 are organic or inorganic radicals. The alkyl radicals X and Y can be the same or different. Each consists of a carbon chain with n carbon atoms. The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms. The radicals Ri and R2 can be the same or different. If they are inorganic radicals, they are hydrogen (H) or chlorine (Cl). If they are organic in nature, they are alkoxy radicals that contain a carbon chain with m carbon atoms. The alkoxy groups consist of 1 <= m <= 4 carbon atoms.

[0046] The silanes can be described by the general molecular formula SiZRiR2R3. Where Z is an organic residue with hydrophobic properties and Ri, R2 and R3 are organic or inorganic residues. The residues Ri, R2 and R3 can be different or the same. If they are inorganic residues, they are hydrogen (H) or chlorine (Cl). If they are organic in nature, they are alkoxy residues that contain a carbon chain with m carbon atoms. The alkoxy groups consist of 1 <= m <= 4 carbon atoms. The organic residue Z can be described by the general molecular formula NX Ai A2 A3 A4. Where N represents a primary, secondary, tertiary or quaternary amine, Ai, A2, A3 and A4 are hydrogen atoms or organic alkyl residues respectively and X is a counterion from the group of halogens or pseudohalogens. The alkyl residues can be the same or different and consist of a carbon chain with n carbon atoms.The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms.

[0047] The silanes can be described by the general molecular formula SiWRiR2Rs. Where W is an organic residue with hydrophilic, ionic and non-ionic properties and Ri, R2 and R3 are organic or inorganic residues. The ionic, organic residue W consists of a carbon chain with n carbons and a terminal, polar group. The carbon chain contains 3 <= n =< 16 carbon atoms, preferably n < 8 carbon atoms. The non-ionic, organic residue W consists of a carbon chain with n carbons and a series of alkoxy units. The carbon chain contains 3 <= n =< 16 carbon atoms, preferably n < 8 carbon atoms. The alkoxy group consists of either ethoxy or propoxy units. These are p repeating units, where 2 <= p <= 15. The residues Ri, R2 and R3 can be different or the same. If the residues are inorganic, they are hydrogen (H) or chlorine (CI).If they are organic in nature, they are alkoxy residues containing a carbon chain with m carbon atoms. Alkoxy groups consist of 1 <= m <= 4 carbon atoms.

[0048] The phosphonic acid derivatives can be described by the general molecular formula RPO(OH)2. R represents an alkyl radical with n carbon atoms, where 3 <= n <= 16.

[0049] The phosphonic acid derivatives can be described by the general molecular formula ZPO(OH)2, where Z is an organic radical with hydrophobic properties. The organic radical Z can be described by the general molecular formula NXAi A2A3A4. N is a primary, secondary, tertiary, or quaternary amine, Ai, A2, A3, and A4 are hydrogen atoms or organic alkyl radicals, respectively, and X is a counterion from the group of halogens or pseudohalogens. The alkyl radicals can be the same or different and consist of a carbon chain with n carbon atoms. The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms.

[0050] The phosphonic acid derivatives can be described by the general molecular formula ZPO(OH)2. Where Z is an organic residue with hydrophilic, ionic, and non-ionic properties. The ionic, organic residue W consists of a carbon chain with n carbons and a terminal, polar group. The carbon chain contains 3 <= n =< 16 carbon atoms, preferably n < 8 carbon atoms. The non-ionic, organic residue W consists of a carbon chain with n carbons and a series of alkoxy units. The carbon chain contains 3 <= n =< 16 carbon atoms, preferably n < 8 carbon atoms. It consists of either ethoxy or propoxy units. These are p repeating units, where 2 <= p <= 15.

[0051] A magnetic layer can be provided inside the magnetic pigment. The following layers (or layer systems) are possible:

[0052] Iron-silicon alloys with the compositions Fe x Si y and layer thicknesses 0.03 to 0.7 |im

[0053] Magnetic layers made of iron (Fe), cobalt (Co) or nickel (Ni) and their alloys with the compositions Fe x Ni y , Fe x Co y and Ni x Co y

[0054] Aluminium-containing (Al) alloys with the compositions Fe x Al y , Co x Al y and Ni x Al y in layer thicknesses of 0.03 to 1.0 gm Chromium-containing (Cr) alloys and oxides with the compositions Fe x Cr y , Al x Fe y Cr z , CrO?, Co x Al y Cr z and Ni x Al y Cr z in layer thicknesses 0.03 to 1.0 |im

[0055] To produce magnetic pigments, it may be necessary to separate the pigments. This can be achieved, for example, as follows:

[0056] - Separation via dissolver

[0057] - Separation by dispersing systems that operate according to the rotor-stator principle.

[0058] - Separation by using dispersing systems that separate pigments

[0059] Vacuum or low pressure separation. - Separation via a rotating magnetic field, whereby pigments that form conglomerates on top of each other move apart induced by the magnetic field.

[0060] - Use of a rotating permanent magnet

[0061] - Use of a multi-pole electromagnet and electronic generation of a rotating field of any frequency

[0062] - Separation via ultrasound

[0063] - Preliminary demagnetization using a decaying magnetic field and subsequent separation by one of the methods mentioned

[0064] - Preliminary demagnetization by passing through several electrically generated, coupled rotating fields with decreasing field strengths and subsequent separation by one of the methods mentioned

[0065] - Preliminary demagnetization by heating the pigments above their Curie temperature and subsequent cooling. Separation is performed using one of the methods mentioned.

[0066] - Combination of the described methods.

[0067] For the production of magnetic pigments, embossed molds can be used, which can be produced as follows:

[0068] Three different structures can be used in the manufacturing process to produce the pigments. Each of the structures is composed of regular, geometric substructures. These substructures can be, for example, round (e.g., circular, oval, etc.), polygonal (e.g., triangular, quadrangular, pentagonal, hexagonal, heptagonal, octagonal, etc.), or star-shaped (e.g., with 4, 5, 6, 7, 8 or more points). Square or hexagonal substructures are preferably used, with hexagonal substructures being particularly preferred. The pigment size is directly proportional to the size of the geometric substructures. The first structure type can, for example, comprise hexagons that touch at the edges. This means that each hexagon is surrounded by six other hexagons. The hexagons have a height offset, so that no two adjacent polygons are at the same height. The height offset h is 0.5 < h < 4 μm from level to level.Due to its arrangement, this type of structure is referred to as a "plateau structure" below.

[0069] The second structure type also includes hexagons for illustration purposes. In this type, the individual polygons also border each other at their edges, but there is a gap between all edges. All hexagons are essentially at the same height. The gap has a trench-like appearance and has a U-, V-, semicircular, or square cross-section. The trench has a maximum depth t of 6 μm, or 0.5 < t < 6 μm, and a width b of 0.5 < b < 6 μm. This structure type is referred to below as a "trench structure."

[0070] The third structural type also includes hexagons for illustration purposes. In this type, the individual polygons also border each other at their edges, but there is a gap between all edges. All hexagons are essentially at the same height. The gap has a mountain ridge-like appearance and has an inverted U-, V-, semicircular, or square profile in cross-section. The ridge has a maximum height hk of 6 |im, or 0.5 < hk < 6 gm, and a width b of 0.5 < b < 6 m. This structural type is referred to below as a "comb structure."

[0071] The (hexagonal) bases can be slightly offset in height from each other or slightly tilted relative to the base. The second and third structure types can be inverse to each other.

[0072] It is possible to apply additional nanostructures to the regular, geometric substructures. These additional nanostructures can create holographic or other optical or surface effects.

[0073] In structure types two and three, the gaps can be continuous or discontinuous. This can influence the efficiency of the predetermined breaking point.

[0074] In all three structure types, the surfaces are tilted by an angle a. They are therefore not necessarily parallel to the surface and can also be tilted relative to each other. The following applies to the angle a: 0° < a < 90°. A < 45° is preferred, and a < 20° is particularly preferred.

[0075] The three structure types are lithographically etched into a polymer matrix, which is then electroplated and replicated. At the end of this process, a metallic embossing tool is obtained that has the desired structure types and substructures over its entire surface. This embossing tool is used for the subsequent process steps.

[0076] A water-removable, structurable release coat (UV / hot stamping / wash ink) can be used.From DE 10 2021 004984 a method for producing pigments of defined shape and size is known, comprising providing a carrier substrate, coating the carrier substrate with an embossing lacquer that cures by means of UV radiation and can be removed with an aqueous solution after UV curing, introducing defined structures into the embossing lacquer by embossing technology, which structures are decisive for the defined shape and the defined size of the pigments to be produced, UV curing of the embossing lacquer, coating the embossing lacquer with a pigment material layer, treating the resulting layer structure with an aqueous solution in order to remove the embossing lacquer in this way and to release the pigment material layer suitable for providing individual pigments and obtaining the pigments obtainable from the pigment material layer, optionally exerting mechanical stress on the pigment material layer.

[0077] A carrier substrate (e.g. PET film, possibly pre-treated for printing) is treated with corona if necessary and coated with an embossing varnish into which the defined structures are embossed. In addition to the embossed predetermined breaking points, which define the pigment size and shape, structures can optionally be embossed that determine the surface structure of the pigments. These structures can change the physical and optical properties of the pigments or serve as forensic features. The structures can be nanostructures, hologram gratings or microstructures. Typically, the height of these surface structures is smaller than that of the embossed predetermined breaking structures so that these do not function as such. The surface structures embossed into the varnish are transferred to the pigment. After or simultaneously with the embossing of the embossing varnish, the UV embossing varnish is UV cured.Curing with a heated roller when using a hot stamping ink. After curing, the ink layer can be removed with water (water-soluble or water-swellable). It is very advantageous for water removability if the ink layer is not fully cured.

[0078] The degree of curing of the UV embossing lacquer layer during the embossing process could be influenced by the following parameters: type of UV lamp (conventional (iron-doped) medium-pressure mercury lamp or UV LED lamp), quantity of suitable photoinitiators (wavelength-dependent), temperature input during the embossing process, addition of chain transfer agents.

[0079] Suitable raw materials for the UV embossing varnish are prepolymers and / or reactive thinners, such as polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, acryloyl norpholine (see, for example, document EP 3 230 795 B1), and other acrylate-based (co)polymers. The raw materials can, in particular, be water-soluble. For this purpose, a photoinitiator is formulated (e.g., 2-hydroxy-2-methyl-1-phenylpropanone, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, or mixtures thereof) and, if appropriate, additives.

[0080] Formulation examples for a water-swellable UV embossing varnish: o 75-90% Photomer 4159 (IGM) o 5-20% ACMO o 0.5-3% polysiloxane surfactant o 2-7% Omnirad 2100 or o 75-93% Photomer 4056 (IGM) o 5-20% Photomer 4054 o 2-7% Omnirad 2100

[0081] Use of water-removable (possibly water-soluble), optionally UV-curable dual-cure thermoplastics:

[0082] Recipe e.g.: o 95% Laromer 8983 + 5% Irgacure 819 DW o 75% Laromer 8983 + 20% Laromer 9005 + 5% Irgacure 819 DW

[0083] Curing / exposure is only carried out to the extent necessary (film formation and crosslinking) for a good release and subsequent metallization (temperature resistance). Embossing is preferably performed on thermoplastics before optional UV curing.

[0084] Optionally, either the water-soluble / water-swellable varnish embossed with the predetermined breaking structures or the water-insoluble, embossed UV varnish can be printed with a washing ink, which supports the removal of the well-formed pigments in the subsequent washing process or, in the case of the insoluble UV varnish, enables this in the first place.

[0085] Metallization can be carried out as follows:

[0086] After the embossing lacquer has cured, the cured embossing lacquer layer is metallized. The pigment material layer is an optically effective functional layer with an additional magnetic layer, preferably a color-shifting thin-film system with the layer sequence absorber / dielectric / reflector / magnetic layer / reflector / dielectric / absorber or absorber / dielectric / magnetic reflector / dielectric / absorber. The thin-film system can be applied using electron beam evaporation or other common PVD systems.

[0087] If wash ink is used, metallization takes place after the embossing varnish has been printed with the corresponding wash ink.

[0088] Optional washing can be done as follows:

[0089] In a roll-to-roll process, the coated or metallized substrate is passed through a (possibly hot) water bath, and thus (possibly with the help of mechanical processes, such as brushing in a water bath or using a roller in front of the water bath) the water-removable embossing lacquer layer is dissolved or swelled, or the layer of wash ink is dissolved or dispersed, so that the vapor-deposited metallization is, so to speak, blown off and the well-formed, platelet-shaped effect pigments are obtained. If the embossing lacquer is water-soluble, the pigments are separated (e.g. by decanting) and washed. If the embossing lacquer is water-swellable, the pigments are separated from any pieces of embossing lacquer floating in the water that have detached from the carrier substrate (e.g. by decanting, or possibly by separation due to the pigments' magnetic properties).The stripping occurs with water, preferably in a basic water solution (saponification and regeneration of the carbanions). The basicity can be generated using NaOH, ammonia, amines, and salts that react with basic substances in aqueous solution, such as alkali carbonates. Pigment production can also proceed as follows: A water-soluble or water-swellable UV varnish is printed onto a carrier film (e.g., PET, possibly pre-treated), the trench structures are embossed, and cured. This varnish has properties that reduce the adhesion of the metallization. Hot stamping varnishes with corresponding properties are also conceivable for this purpose. This film is vapor-deposited with one of the aforementioned layer structures using the PVD process.

[0090] A second carrier film (e.g., PET, optionally pre-treated) is printed with a preferably water-soluble, adhesive varnish. Both rolls are laminated together so that the printed layers overlap. After a rest period of up to seven days, the films are separated and unwound. The raised, metallized hexagons are transferred to the adhesive film. Individual pigments are obtained by washing the preferably water-soluble, adhesive varnish.

[0091] Drainage 1

[0092] Optionally, a dewatering step can be implemented prior to surface treatment of the pigments if the pigment content in the washing medium is very low (see section "Washing") to concentrate the pigment in the washing medium. This can be achieved, for example, using a decanter centrifuge or a chamber filter press. This produces a filter cake or pigment slurry with a solids content of greater than 5% and less than 95%, which can be separated from the filtrate.

[0093] Surface treatment

[0094] Surface treatment can be achieved using wet-chemical processes. The dehydrated, moist pigments are suspended, for example, in a solvent with a weight fraction w, which can range from 5 to 75%. The solvent is liquid between 5 and 95 °C and can be either organic or inorganic. Suitable solvents include water, lower alcohols with up to six carbon atoms, alkanes with five or more carbon atoms, toluene, xylenes, organic carbonates, DMSO, ketones with up to eight carbon atoms, cyclic and acyclic ethers with two or more carbon atoms, aldehydes with up to six carbon atoms, and carboxylic acids with up to six carbon atoms.

[0095] The pH is adjusted by adding an acid or base that is soluble in the solvent. These acids include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, carbonic acid, citric acid, methane acid, ethanoic acid, oxalic acid, succinic acid, or tartaric acid. Bases include ammonia and its organic derivatives from the amine group, where one, two, or three hydrogen atoms of the ammonia may be substituted by organic radicals, and aqueous solutions of ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide. pH-altering salts of the aforementioned acids and bases can also be used. The desired pH is between pH 2 and pH 11. The acid, base, or salt used must be miscible with the solvent in the amount used; it must not undergo any reactions, side reactions, or form separate phases.

[0096] The reaction mixture is completed by the addition of an organic silane or phosphonic acid derivative. Both classes of compound are intended to improve the surface properties and generally protect the pigments from chemical attack. The improved properties are reflected in increased hydrophilicity, lipophilicity, amphiphilicity and / or additional reactive, organic, functional groups, such as acrylate groups or double bonds. The amount used depends on the amount of pigment used and is between 1 and 10%. < 5% is preferred. Dynasylan PTMO from Evonik Industries AG is mentioned as an example here. Following the addition of the coating material, the reaction mixture reacts in a reactor with continuous stirring or circulation for up to 8 hours. The reaction temperature is between 15 and 80 °C, preferably between 15 and 50 °C.

[0097] The surface can be activated with a hydrogen peroxide solution before the actual treatment step. The hydrogen peroxide content is between 1 and 15%, preferably < 10%.

[0098] Drainage 2

[0099] Before the pigments are finally dried, the reaction reagents used in the surface treatment must be separated from the pigment. The pigment is filtered again through a decanter centrifuge or a chamber filter press, and the filter cake or pigment slurry is obtained. Optionally, the pigment can be resuspended with a cleaning liquid (e.g., water), rinsed, and dewatered again. This produces a filter cake or pigment slurry with a solids content of greater than 5% and less than 95%, which can be separated from the filtrate.

[0100] Drying: To dry the pigment, the moist filter cake / pigment slurry is placed in a drying system. This can be a vacuum dryer, for example. The pigment is finally dried to a residual moisture content of less than 10%.

[0101] Sighting

[0102] Pigment fragments or pigment compounds may also arise during the pigment production process, e.g., due to mechanical stress or pigment bonding during surface treatment, dewatering, or drying. Cyclone classifiers and screening systems can be used to separate the upper and lower grains, i.e., to produce pigments of the desired size.

[0103] Capsules - definition and production

[0104] Definition / goals of encapsulation

[0105] Core-shell system:

[0106] - The pigment is mobile in a liquid core and encapsulated in a solid shell.

[0107] - The pigment floats in the liquid (preferably oil-containing) core

[0108] - The pigment is held in the center by chemical means

[0109] - The pigment is repelled from the capsule wall

[0110] - The capsule contains exactly one pigment or only a few pigments

[0111] The outer diameter of the capsule, D, and the thickness of the capsule shell, h, yield the diameter D' of the liquid capsule core: D' = D - 2h (which corresponds to the inner diameter of the capsule shell). The liquid capsule core is only slightly larger than the pigment:

[0112] 1 <(D - 2h) / d < 2.0, preferably 1.05 < (D - 2h) / d < 1.5, particularly preferably l,l < (D - 2h) / d < 1.4

[0113] The capsule has a precisely defined outer diameter with little fluctuation.

[0114] This fluctuation can be defined, for example, by the target value of the capsule outer diameter D and / or the polydispersity index (PDP):

[0115] 15 pm <= D <= 100 |im + / - 10 pm; preferably 15 gm <= D <= 50 gm + / - 5 gm; particularly preferred 24 |im <= D <= 35 gm + / - 3 gm

[0116] Capsule size distribution characterized as PDP with PDP = (ÖD / D) 2 , where ÖD is the standard deviation of the capsule outer diameter distribution:

[0117] 0 <= PDP < 0.3; preferred 0 <= PDP < 0.2; particularly preferred 0 <= PDP < 0.1

[0118] The capsule distribution can be monomodal (there is exactly one mean capsule outer diameter) or can have, for example, two or three mean capsule outer diameters with the above size distribution (bi- or tri-modal distribution).

[0119] Each capsule contains only a few pigments, preferably fewer than 6, 5, 4, or 2 pigments. Particularly preferably, a capsule contains exactly 1 pigment. Encapsulation processes are used that favor an extremely narrow size distribution of the capsules. The following processes can be used, for example: o Microfluidics

[0120] Use of two or more fluids in a single-stage process Use of two or more fluids in a multi-stage process Step emulsification reactors Co-flow reactors

[0121] Flow-Focusing Reactors

[0122] Microchannel emulsification o co-extrusion

[0123] Use of monocentric or concentric nozzles

[0124] Use of two or more fluids in a single-stage process Use of two or more fluids in a multi-stage process Drop formation by vibration

[0125] Drop formation via periodic pressure fluctuations of the continuous / external phase

[0126] • Description of capsule production by microfluidics

[0127] The capsules can be manufactured using microfluidics. Microfluidics is able to safely handle the small volume of liquid within the capsule. Typically, volumes in the range of 1(E 9 to IO 18Liters processed. Numbering up allows larger volumes to be used and processed. Microdroplets are required to produce the microcapsules. Microdroplets can be generated using T- and Y-shaped cross-flow geometries, co-flow geometries, flow-focusing geometries, microchannel emulsification geometries, and step emulsification geometries. Combinations of the basic geometries mentioned have also proven suitable. Preferred geometries must be capable of processing at least two fluids. These fluids must be immiscible and can differ in their polarities, viscosities, and compositions. The diameters of the structures are on the order of the required droplet sizes, d < 100 μm. Inflow and outflow ports of all fluids can be larger. Furthermore, the structures must be capable of achieving the required polydispersity index values.

[0128] In its simplest form, this method requires two different fluids for microdroplet or microcapsule formation. One fluid, A, represents the dispersive phase to be dropped into drops. The other fluid is the continuous phase B. The disperse phase A contains the pigments, additives, and dissolved, crosslinkable polymers. The disperse phase is generally non-polar and oleophilic. The continuous phase is more hydrophilic and contains, in addition to additives, a dissolved crosslinker. Additives include all chemicals that change the interfacial properties, rheological properties, density, or optical properties. The crosslinked polymer can come from the group of polyurethanes, polyacrylates, polymethacrylates, polyamides, polyacrylonitriles, polycarbonates, melamine resins, or polyesters. The polymer must only be soluble in the dispersive phase B.The crosslinker, on the other hand, must only be soluble in the continuous phase A. During the dropletization process, droplet formation occurs, which is caused by the different hydrophilic and lipophilic nature of the fluids and the desire to minimize surface area. The use of additives significantly increases the stability of the formed droplets. At the interface between the discontinuous and continuous phases, a reaction occurs between the crosslinkable polymer and the crosslinker. Depending on the reaction time, a polymer skin or wall forms. By varying the fluid pressures or volume flows, the quantity of capsules formed and their diameter can be directly influenced.

[0129] The reaction can start without external influence or be initiated by changing the temperature, changing the pH value or IR / UV radiation.

[0130] Droplet and capsule formation can also occur by swapping the two phases and their properties. Careful consideration of the materials and equipment is essential in this case.

[0131] The separation of filled and empty capsules can be achieved using a static or dynamic, magnetic, or electric field. Separation and sorting using the Lorentz force is also possible. Another option for separation and classification is the use of spiral-shaped structures. These structures enable the separation of the capsules due to their different flow properties.

[0132] Finally, the formed capsules are separated from the continuous phase and dried.

[0133] In more complex encapsulation arrangements, three or more fluids can be used. This involves at least one pigment-containing, dispersed phase, a similarly dispersed phase that forms the future capsule shell, and a continuous phase that separates the formed droplets. The capsule shell phase can consist of a prepolymer or polymer solution and can either react with one of the other fluids or form the capsule wall through IR / UV radiation or temperature changes.

[0134] The formation of a capsule from more than three fluids can be based on one or more microfluidic processes.

[0135] Droplet and capsule formation can also occur by swapping the two phases and their properties. Careful consideration of the materials and equipment is essential in this case.

[0136] In order to achieve a high capsule fill rate and avoid a high number of empty capsules, it can be advantageous to support the advance of the magnetic pigments with the disperse phase A using a moving magnetic field. In a preferred embodiment, similar to a linear motor with an electromagnetically excited stator, the poles of an at least two-phase arrangement of electromagnets are arranged alternately along the feed of phase B. As with a stepper motor, the phases of the electromagnets are controlled with a phase offset, so that a moving magnetic field is formed along the feed channel of phase A, which transports the pigments individually at the appropriate speed to the position of drop formation. The control frequency of the at least two-phase electromagnet is varied according to the conveyor speed to be set.

[0137] The pressure p used to convey the continuous phase can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. By suitable placement and design selection of the microfluidic structures, the conveyance of the continuous phase can be dispensed with and a beaker or other container filled with the continuous phase can be used. This container functions as part of the droplet formation and at the same time as a possibility for storing, saving or temporarily storing formed droplets or capsules. Use as a curing bath is also conceivable. The continuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver or a pump.

[0138] The pressure p used to convey the dispersed phase can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. The discontinuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver, or a pump.

[0139] All liquids used as disperse or continuous phases have a processing temperature between -15 and +60 °C, preferably between 0 and 45 °C and particularly preferably between 15 and 35 °C.

[0140] All liquids used as a disperse or continuous phase have a solidification temperature below 0 °C, preferably below -15 °C, and particularly preferably below -25 °C. Furthermore, they have a boiling point above 105 °C, preferably above 150 °C, and particularly preferably above 250 °C. All liquids used as a disperse or continuous phase have a viscosity between 0.2 and 150 mPa*s, preferably between 10 and 100 mPa*s. Changing the viscosity through the addition of rheological additives, temperature changes, or partial polymerization is possible. Reversible increasing and / or reducing the viscosity, for example, through guar gum and its derivatives and with the aid of temperature, time, and pH changes, is also possible.

[0141] All liquids used as disperse or continuous phase must have a density between 500 and 5000 kg / m3 , preferably between 800 and 3400 kg / m 3 This density can be changed by dilution or concentration. A change in density by changing the temperature or pH is conceivable. The density can be increased, for example, by dissolving sodium polytungstate. The addition of additives such as tungsten carbide to further increase the density is possible.

[0142] The liquids used as the dispersed or continuous phase can be organic, inorganic, or mixed. Mixtures of organic and inorganic liquids are conceivable in any chemically and physically possible ratio. These substances are defined in more detail below.

[0143] In the narrower sense, organic liquids include natural and artificial triglycerides and other esters of saturated and mono- or polyunsaturated fatty acids. These also include triglycerides and esters consisting of saturated and mono- or polyunsaturated fatty acids, and mixtures of triglycerides and esters consisting of saturated and mono- or polyunsaturated fatty acids. Fatty acids are considered to be aliphatic monocarboxylic acids with at least six carbon atoms. The corresponding esters can be formed with simple or polyhydric alcohols and glycerin. The esterification of the alcohol or organic acid does not have to be complete. Examples include sunflower oil, soybean oil, and peanut oil.

[0144] The use of mono- or dicarboxylic acids that are monounsaturated or polyunsaturated is also conceivable. Esters and triglycerides, as well as amides of the aforementioned acid types, are also possible. Examples include stearic acid, caprylic acid, and butyric acid.

[0145] The use of linear, branched, cyclic, aromatic, saturated and unsaturated mono- and polyols, such as propanediol and hexanol, is conceivable.

[0146] Other organic liquids that can be used include mixed and / or pure, aliphatic and / or aromatic, branched and / or unbranched, and n- and / or iso-hydrocarbons and their mixtures. White spirits are examples of this.

[0147] Water is one of the inorganic liquids.

[0148] Other inorganic liquids include aqueous solutions of inorganic salts and gases in all possible concentrations and mixtures. For example, aqueous polytungstate solutions can be used.

[0149] Aqueous solutions of organic salts such as sodium dodecyl sulfate and solutions of organic, water-soluble compounds such as acetic acid and ethanol are considered mixed-nature liquids. Silicone oils also fall into this group.

[0150] Description of capsule production by co-extrusion

[0151] The process is divided into extrusion and co-extrusion. The difference lies in the number of fluids used. In extrusion, only one fluid is used. The materials used and process parameters are described after the description of the manufacturing process.

[0152] There are basically two methods for forming droplets. The first method involves exciting a nozzle to cause it to vibrate. The amplitude and frequency have a significant influence on droplet formation. The prediction can be made, for example, using the Rayleigh instability. This method is known as vibration technology. Droplet formation can be achieved by deliberately pulsing the liquid. The second method involves deliberately breaking off a droplet by a fluid flowing past. This can be either a liquid or a gas; accordingly, the method is called the airjet or flow focusing process. One influencing factor here is, for example, the ratio of the flow velocities to one another. Both methods enable a very narrow droplet size distribution.

[0153] During extrusion, a liquid is formed into droplets using the methods mentioned above. This liquid contains not only the pigment but also surface additives and a reactive prepolymer. The prepolymer can be crosslinked, for example, by IR / UV radiation, a gas, or a curing bath. Curing can then occur in free fall by IR / UV radiation or gas, or in the curing bath by a crosslinking component, UV radiation, or temperature changes. The curing bath and the pigment-containing liquid must be immiscible. The curing time determines the hardness and thickness of the capsule wall.

[0154] In co-extrusion, two or more liquids flow through a concentric nozzle, forming a multi-layered fluid jet. The liquids are immiscible. Droplet formation occurs either by the outermost liquid flowing past, by pulsing one or more liquids, or by vibration. The outermost liquid is the continuous phase, while the other liquids form the discontinuous phase. The capsule wall can be created in several ways. It can occur through interfacial polymerization at the interface between the continuous and discontinuous phases. One phase contains the prepolymer and the other the crosslinker. Another method is for the continuous phase to be cured in free fall by IR / UV radiation, a gas, a bath, or a combination thereof.The third method is curing one of the outer, dispersed phases using IR / UV radiation or an immiscible curing bath. A gas could also be used for curing if the concentration and residence time are sufficient. Combinations of the processes are also possible here.

[0155] The capsules produced in this way can additionally be cross-linked or surface treated.

[0156] The finished capsules are dried.

[0157] In the final step, the capsules are sorted according to functionality and dispersity. Functional capsules can be separated using a magnetic or electromagnetic field. Sieve or flow classification can be used to separate the desired capsule sizes.

[0158] The nozzle vibrates at a frequency f between 0 and 20,000 Hz and preferably between 500 and 5,000 Hz. The vibration follows a sine wave.

[0159] The flow ratio of continuous and discontinuous phases to each other is < 2:1, preferably < 5:1 and particularly preferably < 10:1.

[0160] The surface additives used can be nonionic, anionic, cationic, or amphoteric surfactants. Nonionic surfactants include polyalcohols, ethers, and their combinations in the form of ethoxylates. Anionic and cationic surfactants used include carboxylates, sulfonates such as sodium dodecylbenzylsulfonate, sulfates such as sodium dodecyl sulfate, and quaternary ammonium compounds. Zwitterionic surfactants include betaines such as cocoamidopropyl betaine and sultaines.

[0161] The pressure p used to convey the continuous phase can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. By appropriately positioning the microfluidic structures, the conveyance of the continuous phase can be dispensed with and a beaker or other container filled with the continuous phase can be used. This container functions as part of the droplet formation and at the same time as a possibility for storing, saving or temporarily storing formed droplets or capsules. Use as a curing bath is also conceivable. The continuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver or a pump.

[0162] The pressure p used to convey the dispersed phase can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. The discontinuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver, or a pump.

[0163] All liquids used as disperse or continuous phase have a processing temperature between -15 and +60 °C, preferably between 0 and 45 °C and particularly preferably between 15 and 35 °C.

[0164] All liquids used as a disperse or continuous phase have a solidification temperature below 0 °C, preferably below -15 °C, and particularly preferably below -25 °C. Furthermore, they have a boiling temperature above 105 °C, preferably above 150 °C, and particularly preferably above 250 °C.

[0165] All liquids used as a disperse or continuous phase must have a viscosity between 0.2 and 150 mPa*s, preferably between 10 and 100 mPa*s. Viscosity can be altered by adding rheological additives, temperature changes, or partial polymerization. Reversible viscosity increases and / or decreases, for example, using guar gum and its derivatives and by adjusting temperature, time, and pH, are also possible. All liquids used as a disperse or continuous phase must have a density between 500 and 5000 kg / m³. 3 , preferably between 800 and 3400 kg / m 3This density can be changed by dilution or concentration. A change in density by changing the temperature or pH is conceivable. The density can be increased, for example, by dissolving salts such as sodium polytungstate. The addition of additives such as tungsten carbide to further increase the density is possible.

[0166] The liquids used as the dispersed or continuous phase can be organic, inorganic, or mixed. Mixtures of organic and inorganic liquids are conceivable in any chemically and physically possible ratio. These substances are defined in more detail below.

[0167] In the narrower sense, organic liquids include natural and artificial triglycerides and other esters of saturated and mono- or polyunsaturated fatty acids. These also include triglycerides and esters consisting of saturated and mono- or polyunsaturated fatty acids, and mixtures of triglycerides and esters consisting of saturated and mono- or polyunsaturated fatty acids. Fatty acids are considered to be aliphatic monocarboxylic acids with at least six carbon atoms. The corresponding esters can be formed with mono- or polyunsaturated alcohols and glycerol. The esterification of the alcohol or organic acid does not have to be complete. Examples include sunflower oil, soybean oil, and peanut oil.

[0168] The use of mono- or dicarboxylic acids that are monounsaturated or polyunsaturated is also conceivable. Esters and triglycerides, as well as amides of the aforementioned acid types, are also possible. Examples include stearic acid, caprylic acid, and butyric acid.

[0169] The use of linear, branched, cyclic, aromatic, saturated and unsaturated mono- and polyols, such as propanediol and hexanol, is conceivable.

[0170] Other organic liquids that can be used include mixed and / or pure, aliphatic and / or aromatic, branched and / or unbranched, and n- and / or iso-hydrocarbons and their mixtures. White spirits are examples of this.

[0171] Water is one of the inorganic liquids.

[0172] Other inorganic liquids include aqueous solutions of inorganic salts and gases in all possible concentrations and mixtures. For example, aqueous polytungstate solutions can be used.

[0173] Aqueous solutions of organic salts such as sodium dodecyl sulfate and solutions of organic, water-soluble compounds such as acetic acid and ethanol are considered mixed liquids. Silicone oils also fall into this group.

[0174] The temperature of the curing bath can be between -15 and +60 °C, preferably between 0 and 45 °C, and most preferably between 15 and 35 °C. Isocyanates such as TDI and MDI, glutaraldehyde, and formaldehyde can be used as curing components in the curing bath. The use of dicarboxylic acids is also conceivable. Post-curing can be carried out with the same chemicals, if necessary.

[0175] The prepolymer can be acrylates or methacrylates, more precisely epoxy acrylates, polyester acrylates, polyether acrylates, urethane acrylates.

[0176] The curing time can be up to 48 h, preferably < 24 h, most preferably < 1 h.

[0177] The finished capsules are dried at < 200 °C, preferably < 150 °C.

[0178] If the formation of the capsule wall occurs through cooling and the resulting solidification of one or more phases, then the melting temperature of this phase(s) is at least 150 °C, preferably 200 °C and most preferably 250 °C.

[0179] • Description of other encapsulation methods for narrow monomodal distribution

[0180] In the following, further processes are named which are generally suitable for the formation of droplets with a narrow size distribution.

[0181] Electrostatic droplet deposition: Applying a voltage to the liquid being deposited and the liquid being deposited creates an electrostatic force. This helps overcome the adhesion force. This process is suitable for producing droplets with sizes between 300 μm and 5 mm in very narrow size distributions. In experiments, droplet sizes were reduced to approximately 50 μm in diameter. Curing of the pigment-containing disperse phase would again occur through an immiscible curing bath or during free fall with IR / UV radiation, a gas, and / or a combination. Curing by temperature variation is also possible.

[0182] Jet Cutter Process: In the jet cutter process, a laminar liquid jet is forced through a nozzle at high speed. Directly below the nozzle is a rotating disc, which uses thin wires to cut cylindrical segments from the jet. Surface tension then causes the cylinders to form spherical droplets. Droplet formation is based on the mechanical impact of the liquid jet on the cutting wire. This impact causes a cut, creating the cylindrical section and a cutting loss. Cutting loss can be considered, as a first approximation, to be a cylinder with the height of the wire diameter. This cylinder is projected outward, where it is collected and recovered. Droplet formation is solely due to the mechanical cutting and surface tension.The viscosity of the fluid has no direct influence, which means that even highly viscous liquids can be processed. The droplet sizes range from a few hundred micrometers to several millimeters. The most important influencing factors are the nozzle diameter, the flow rate at the nozzle, the number of cutting wires, and the rotation speed of the cutting tool. To achieve a narrow size distribution, the flow through the nozzle must be even. The pumps used must therefore operate without pulsation. In addition, the cutting tool must have a constant rotation speed. The tool itself must also meet certain requirements. The wires must be evenly spaced from one another and they must always be taut. The thinner these wires, which are usually made of stainless steel or, increasingly, polymer fibers, are, the less cutting loss occurs.Here, too, curing of the pigment-containing, dispersed phase can occur either in the gas phase by IR / UV radiation, a gas, and / or in an immiscible curing bath. Curing by temperature variation is also possible.

[0183] Hydrophobization of the pigments can be advantageously used to significantly improve stability and separation in non-polar carrier liquids.

[0184] Furthermore, experiments have shown that the settling stability of dispersions in oils and paraffin oils improves significantly with the length of the alkyl residues in the surface treatments. The best results are obtained with C8 and C16 alkyl residues.

[0185] It has been shown that monodisperse capsules do not pose a problem, whether they have a liquid core or are fully hardened. The targeted coating / encapsulation of solid particles is also possible. There is work in microbiology in which human egg cells (d = 200 gm) and liver cells (d = 70 gm) are individually encapsulated. In this technology, spherical nanoparticles are packaged in capsules of the same size for use in display technology. The current status is that particles and suspensions of a similar size to the present invention (± one order of magnitude) can be packaged in monodisperse capsules. What is new is that flat particles, which are almost two-dimensional, are encapsulated. Biological cells and nanoparticles, on the other hand, are almost spherical.

[0186] The combination of well-formed pigments with a precisely defined diameter, together with one of the described microencapsulation processes, which enables a very narrow size distribution of the capsules, leads to the desired result: the encapsulation of a pigment with a precisely defined outer contour and size in a capsule of precisely defined size. This combination also offers the advantage of realizing a brilliant, interactive magnetic security feature with a clearly visible color change.

[0187] Printing ink and printing - definition and production

[0188] High area coverage of functional capsules (optically variable elements according to the invention): o The densest sphere packing in one and two layers is aimed for o > 80% of the capsules are functional o Preferred: > 90% of the capsules are functional o Magnetic sorting of the capsules before color production

[0189] • Drying oxidatively or radiation-induced o UV drying o Electron beam drying o Cross-linking between capsule material and binder advantageous

[0190] • Resistance of the ink layer and capsules to the usual chemical and physical banknote resistance tests

[0191] • Insertion in hybrid windows or in the classic BN window (Euro) • Print layer thickness < 100 μm, preferably < 60 μm, particularly preferred <= 40 μm

[0192] • Printing process: gravure, intaglio, screen printing, preferably screen printing

[0193] Design - Easier recognition of the security feature

[0194] Through clever design, the recognition and verification of the security feature is made easier, thus increasing security.

[0195] • Increased contrast by

[0196] Dark or black background print

[0197] Coloring of the binder in a shift color of the ColorShift pigment

[0198] Coloring the background print in a shift color of the ColorShift pigment

[0199] • Strengthening the recognition effect

[0200] Completion of previously only partially recognizable information, e.g. a currency symbol or a value

[0201] Revealing concealed information, e.g., through split printing of fixed capsules or a very similar color and functional capsules. The concealed information is then revealed by the movement of a magnet beneath the security element, creating a dynamic color effect that visually differentiates the functional capsules from the fixed area.

[0202] The capsules and color systems according to the invention can also be used to protect branded goods against product piracy and for authenticating ID documents. The invention is explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also disclose features essential to the invention. These exemplary embodiments are for illustrative purposes only and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components should not be interpreted as meaning that all of these elements or components are necessary for implementation. Rather, other exemplary embodiments may also contain alternative elements and components, fewer elements or components, or additional elements or components.Elements or components of different embodiments may be combined with one another unless otherwise stated. Modifications and variations described for one of the embodiments may also be applicable to other embodiments. To avoid repetition, identical or corresponding elements in different figures are designated by the same reference numerals and are not explained more than once. The figures show:

[0203] Fig. 1 a value document 4 with a security feature 2;

[0204] Fig. 2 is an enlarged partial sectional view taken along section line AA in Fig. 1;

[0205] Fig. 3 is an enlarged partial sectional view of Fig. 2 with a local magnetic field applied;

[0206] Fig. 4 is an enlarged partial sectional view of Fig. 2 with a local magnetic field applied which has a different orientation than in Fig. 3;

[0207] Fig. 5 is a flow chart explaining the generation of the security feature 2 in Fig. 1;

[0208] Fig. 6 is a flow chart for explaining the process section G1 in Fig. 5; Fig. 7 is a flow chart for explaining the process section G3 in Fig. 5, and

[0209] Fig. 8 is a flow chart explaining process section G5 in Fig. 5.

[0210] In the embodiment shown in Fig. 1, the optically variable elements 1 according to the invention are provided as a component of a printing ink as a security feature 2 on a top side 3 of a valuable document 4 (such as a banknote). To better explain the invention, the optically variable elements 1 are not drawn to scale but are shown significantly enlarged and schematically.

[0211] As can be seen in particular from the enlarged partial sectional view in Fig. 2, each optically variable element 1 comprises a capsule 5 with a solid shell 6 and a liquid core 7. Within the shell 6 and thus in the liquid core 7 floats a magnetic color pigment 8 which is flat or plate-shaped and here has a circular outer contour (Fig. 1) with a diameter d (maximum lateral extent d) (Fig. 2).

[0212] Since the capsule 5 is spherical with an outer diameter D and an inner diameter D' that is greater than the maximum lateral extent d of the magnetic color pigment 8, the magnetic color pigment 8 is provided so as to be freely rotatable in the capsule 5. As can be seen from the enlarged sectional view in Fig. 2, the magnetic color pigments 8 are aligned parallel to the upper side 3 or randomly distributed without the application of a local external magnetic field, so that a viewer looking at the upper side 3 perceives the color of the magnetic color pigments 8 in a first form. If a local external magnetic field is now provided in the area of ​​the security feature 2 by means of the magnet 9 shown schematically in Fig. 3, the magnetic color pigments 8 will align themselves along the magnetic field lines (shown schematically as dotted lines), as shown in Fig. 3.In this case, a viewer looking at the top side 3 of the value document 4 will essentially perceive the area of ​​the top side 3 below the security feature 1.

[0213] Of course, it is possible to vary the orientation of the local magnetic field and thus the alignment of the magnetic color pigments 8 within the capsules 5, as schematically shown in Fig. 4. In this case, the magnetic color pigments 8 are inclined by approximately 45° relative to the upper side 3.

[0214] Thus, any angle of inclination of the magnetic color pigments 8 relative to the top side 3 can be set by aligning the local magnetic field. If the magnetic color pigments 8 have not just a simple color layer, but, for example, a color-shifting coating (e.g., a corresponding interference structure with, e.g., a reflector dielectric, a partially reflective cover layer), these color-shifting effects can be generated for a viewer of the top side 3 by changing the angle at which the magnetic color pigments 8 are oriented to the top side 3. By moving the magnet accordingly, dynamic, high-contrast color effects can then be observed, underscoring the special security character of the novel security element.

[0215] The magnetic color pigments 8 all have the same outer contour. This can be, for example, round (circular, oval, etc.), polygonal (e.g., triangular, square, rectangular, hexagonal, octagonal), or star-shaped (e.g., with four, five, six, seven, eight, or more points).

[0216] The maximum lateral dimension d can be greater than or equal to 10 μm and less than or equal to 50 μm. In particular, the variation of the maximum lateral dimension d is relatively small. Thus, a polydispersity index PDI = (δd / d) 2 , where oa is the standard deviation of the distribution of the maximum lateral extent d, greater than or equal to 0 and less than 0.2, preferably less than 0.01, particularly preferably less than 0.003.

[0217] The thickness of the magnetic color pigments 8 can be in the range of 0.5 to 4 gm, preferably in the range of 0.7 to 3 gm and particularly preferably in the range of 0.8 to 2 gm.

[0218] The liquid core 7 can, in particular, be a preferably oil-containing core. Furthermore, the magnetic color pigment 8 and the capsule wall are designed such that the magnetic color pigment 8 is repelled by the capsule wall. The inner capsule diameter D' results from the outer diameter D of the capsule 5 less twice the thickness h of the capsule shell. The inner diameter D' of the capsule 5 is preferably only slightly larger than the maximum lateral extent d of the magnetic color pigment 8. In particular, the following condition can be met: 1 < D' / d < 2.0, preferably 1.05 < D' / d < 1.5 and particularly preferably 1.1 < D' / d < 1.4.

[0219] The outer diameter D of the capsule 5 can, for example, be greater than or equal to 15 μm and less than or equal to 100 μm with a tolerance of + / - 10 μm. Preferably, the outer diameter D can be greater than or equal to 15 μm and less than or equal to 50 μm with a tolerance of + / - 5 μm, and particularly preferably, the capsule outer diameter D can be greater than or equal to 24 μm and less than or equal to 35 μm with a tolerance of + / - 3 μm.

[0220] A polydispersity index PDE = (ÖD / D) 2 for the outer diameter D of the capsules 5, where ÖD is the standard deviation of the capsule outer diameter distribution, can satisfy the following condition: 0 < PDE < 0.3, preferably 0 < PDE < 0.2 and particularly preferably 0 < PDE < 0.1.

[0221] Each capsule 5 preferably contains only a few color pigments 8, in particular each capsule 5 contains one to five color pigments 8. Preferably each capsule 5 contains fewer than four color pigments 8 and particularly preferably each capsule 5 contains exactly one color pigment 8.

[0222] The process steps for producing the optically variable elements 1 and for generating the security feature 2 are described below as examples.

[0223] In order to produce the optically variable elements 1, the magnetic color pigments 8 are produced in a process step Gl (Fig. 5).

[0224] In a process step G2, the magnetic color pigments 8 thus produced are dispersed in the core liquid for the liquid cores 7.

[0225] In a subsequent process step G3, the magnetic color pigments 8 dispersed in the core liquid are then encapsulated.

[0226] In process step G4, the optically variable elements 1 thus produced are then sorted and / or quality tested. In order to be able to produce the desired security element 2, a corresponding printing ink with the optically variable elements 1 is produced in a subsequent process step G5.

[0227] In process step G6, the desired security feature 2 is then printed on the top side 3 of the value document 4 using the printing ink from process step G5.

[0228] Process steps G1, G3, and G5 are described in more detail below. In process step G1, an embossing mold for producing the color pigments 8 is produced in a first step S1.

[0229] In step S2, a lacquer is applied, which is then embossed in step S3 using the embossing mold from step S1. In an optional step S4, a wash ink can be applied. In step S5, metallization is performed, followed by a washing step (step S6) and an initial dewatering step (step S7). This is followed by a surface treatment (step S8) and dewatering and drying (step S9).

[0230] For encapsulation of the pigments according to process section G3, a separate transport of the pigments in the core fluid can be carried out in step S10. In step SH, the pigments are stabilized in the core center.

[0231] In step S12, droplet and interfacial formation occurs, followed by capsule formation / interfacial polymerization in step S13. To produce the printing ink, the capsules 5 are dispersed in a binder (step S14). This is followed by ink formulation with a drying system (e.g., oxidative, UV, radiation-curing, etc.) in step S15. Quality assurance, such as a rheological measurement, can then be performed in step S16.

[0232] List of reference symbols

[0233] 1 optically variable element 2 security feature

[0234] 3 Top

[0235] 4 Valuable document

[0236] 5 capsules

[0237] 6 solid shell 7 liquid core

[0238] 8 magnetic color pigment

[0239] 9 Magnet

Claims

Patent claims 1. Method for producing optically variable elements, comprising a pigment production step in which a plurality of magnetic color pigments (8) are produced such that they are flat, have the same outer contour with a maximum lateral extent d and satisfy the following condition A: 0 < (pa / d) 2 < 0.2, where pa is the standard deviation of the distribution of the maximum lateral extent d, and an encapsulation step in which at least one magnetic color pigment (8) is encapsulated such that a plurality of capsules (5) with a solid shell (6) and a liquid core (7) in which the at least one magnetic color pigment (8) floats and is thus magnetically alignable are present.

2. Method according to claim 1, wherein in the encapsulation step one to a maximum of five magnetic color pigments (8) are encapsulated in each capsule (5).

3. A method according to claim 1 or 2, wherein in the encapsulation step the capsules (5) are produced such that the shell (6) of the capsules (5) has an outer diameter D and the following condition B is met: 0 < (pD / D) 2 < 0.3, where po is the standard deviation of the distribution of the outer diameter D.

4. Method according to one of the above claims, wherein in the pigment production step the magnetic color pigments (8) are provided with an optically variable thin-film system.

5. Method according to claim 4, wherein the liquid core (7) of the capsules (5) and / or the solid shell (6) of the capsules (5) is colored in a color that can be produced by the optically variable thin-film system of the magnetic color pigments (8).

6. Method according to any of the above claims, wherein the pigment production step and the encapsulation step are carried out such that the following condition C is satisfied: 1 < D' / d < 2.0, where D' is the inner diameter of the capsule (5).

7. Method according to one of the above claims, wherein in the pigment production step the magnetic color pigments (8) are produced with a thickness of greater than or equal to 0.5 gm and less than or equal to 4 gm and a maximum lateral extent d of greater than or equal to 0.5 gm and less than or equal to 50 gm.

8. Method according to one of the above claims, wherein in the pigment production step the magnetic color pigments (8) are produced with a monodisperse pigment size distribution, wherein for all magnetic color pigments (8) there is an average value for the maximum lateral extent d that satisfies condition A.

9. Method according to any one of claims 1 to 7, wherein in the pigment production step the magnetic color pigments (8) are produced with a bi- or trimodal pigment size distribution, wherein for the magnetic color pigments (8) there are two or three mean values ​​for the maximum lateral extent d that satisfy condition A.

10. Optically variable elements for producing a printing ink and / or a security feature, wherein the optically variable elements (1) each comprise a capsule (5) with a solid shell (6) and a liquid core (7), wherein in each capsule (5) at least one magnetic color pigment (8) floats in the liquid core and is thus magnetically alignable, wherein the magnetic color pigments (8) are flat, have the same outer contour with a maximum lateral extent d and are produced such that the following condition A is satisfied: 0 < (pa / d) 2< 0.2, where pa is the standard deviation of the distribution of the maximum lateral extent d.

11. Optically variable elements according to claim 10, wherein one to a maximum of five magnetic color pigments (8) are encapsulated in a capsule (5).

12. Optically variable elements according to claim 10 or 11, wherein the capsules (5) are manufactured such that the shell (6) of the capsules (5) has an outer diameter D and the following condition B is satisfied: 0 < (pD / D) 2 < 0.3, where po is the standard deviation of the distribution of the outer diameter D.

13. Optically variable elements according to one of claims 10 to 12, wherein the magnetic color pigments (8) comprise an optically variable thin-film system.

14. Optically variable elements according to claim 13, wherein the liquid core (7) of the capsules (5) and / or the solid shell (6) of the capsules (5) are in a optically variable thin-film system of magnetic color pigments (8) produceable color are colored / is.

15. Optically variable elements according to any one of claims 10 to 14, wherein the following condition C is satisfied: 1 < D' / d < 2.0, where D' is the inner diameter of the capsule (5).

16. Optically variable elements according to any one of claims 10 to 15, wherein the magnetic color pigments (8) have a thickness greater than or equal to 0.5 µm and less than or equal to 4 gm and a maximum lateral extent d of greater than or equal to 0.5 gm and less than or equal to 50 gm.

17. Security feature for arrangement on a value element, in particular a value document, wherein the security feature comprises a plurality of optically variable elements according to any one of claims 10 to 16.

18. Data carrier, in particular chip card, identity document and / or security document, with a security feature according to claim 17.

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