DE102022002099A1 - Method for producing optically variable elements and optically variable elements for producing a printing ink and/or a security feature - Google Patents

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 flat, have the same outer contour with a maximum lateral extent d and the following condition A: 0 ≤ (ρd/ d)2 < 0.2, where ρd 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 in such a way 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 can therefore be magnetically aligned.

Description

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

The optically variable elements are used for design purposes, but also in and/or as a feature of authenticity. Such an authenticity feature, also referred to as a security feature, can, for example, have a special optical representation depending on the viewing angle. For example, variable optical reproduction due to magnetic influence is known. Previous optically variable elements, which are known due to magnetic action, include platelet-shaped, optically variable mica pigments, which are encapsulated in a capsule with an enveloping liquid. When viewed from above without a magnetic field, a cloudy or inconsistent color impression is visible depending on the layers of the platelet-shaped pigments in the capsule. When a magnetic field is applied, these plates align themselves according to the magnetic field.

However, the contrast that can be achieved is low because the capsules are of different sizes and are sometimes filled with many pigments. These can lead to light scattering and thus to poor contrast. Furthermore, the pigments can block each other in the capsule, so that the desired orientation cannot be reproducibly provided by applying an external magnetic field. It has also been found that the printing ink contains many capsules that do not contain any pigments or that the pigments contained in the capsule are immobile and therefore cannot contribute to the effect described. Furthermore, the capsules produced have a large variance in diameter, so that very large capsules potentially clog the screen printing screen for applying the printing ink and small capsules can no longer contribute to the movement effect and contrast. Finally, the print layer has many defects, which further leads to low contrast. This can be caused, for example, by clogged openings in the screen during screen printing due to capsules that are too large.

Based on 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.

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

• - einen Pigmenterzeugungsschritt, in dem eine Mehrzahl von magnetischen Farbpigmenten so hergestellt werden, dass sie flach (bzw. plattenförmig) ausgebildet sind, eine gleiche Außenkontur mit einer maximalen lateralen Ausdehnung d aufweisen und die folgende Bedingung A erfüllen: 0 ≤ (ρ_d / d)² < 0,2, wobei ρ_d die Standardabweichung der Verteilung der maximalen lateralen Ausdehnung d ist, und
• - einen Verkapselungsschritt, in dem jeweils mindestens ein magnetisches Farbpigment so verkapselt wird, dass eine Mehrzahl von Kapseln mit fester Hülle und flüssigem Kern, in dem das mindestens eine magnetische Farbpigment schwimmt und somit magnetisch ausrichtbar ist, vorliegt.

The method according to the invention for producing optically variable elements can have the following steps:

• - a pigment production step in which a plurality of magnetic color pigments are produced in such a way that they are flat (or plate-shaped), have the same outer contour with a maximum lateral extent d and meet the following condition A: 0 ≤ (ρ _d / d ) ² < 0.2, where ρ _d 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 can therefore be magnetically aligned, are present.

An essential point in 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 extent d.

This can be achieved, for example, by using a laser writer to write 3D structures into a photoresist and then vaporizing them with color shift interference layers. This allows e.g. B. hexagonal pigments with a diameter of approximately 25 μm can be produced.

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

The capsules can be manufactured in the encapsulation step so that the shell of the capsules has an outer diameter D and the following condition B is satisfied: 0 ≤ (ρ _D / D) ² < 0.3, where ρ _D is the standard deviation of the distribution of the outer diameter D is.

In the pigment production step, the magnetic color pigments can be provided with an optically variable thin-film system.

The pigment production step and the encapsulation step can be carried out so that the following condition C is satisfied: 1 < D'/d < 2.0, where D' is the inner diameter of the capsule.

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

The magnetic color pigments can be produced in the pigment production step with a monodisperse pigment size distribution, with a single average value for the maximum lateral extent d satisfying condition A being present for all magnetic color pigments.

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

If there is a bi- or tri-modal pigment size distribution, 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 mono-modal pigment size distribution is then present.

The encapsulation step may include 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 can be made to repel each other.

• 0 ≤ (ρd / d)² < 0,2, wobei ρ_d die Standardabweichung der Verteilung der maximalen lateralen Ausdehnung d ist.

Optically variable elements are also provided for producing a printing ink and/or a security feature,
wherein the optically variable elements each comprise a capsule with a solid shell and a liquid core,
whereby at least one magnetic color pigment floats in the liquid core in each capsule and can therefore be aligned magnetically,
wherein the magnetic color pigments are flat, have the same outer contour with a maximum lateral extent d and are manufactured in such a way that the following condition A is fulfilled:

• 0 ≤ (ρd / d) ² < 0.2, where ρ _d is the standard deviation of the distribution of the maximum lateral extent d.

One to a maximum of five magnetic color pigments can be encapsulated in a capsule. Each capsule preferably contains fewer than four or three magnetic color pigments and particularly preferably each capsule contains exactly one magnetic color pigment.

• 0 ≤ (ρ_D / D)² < 0,3, wobei ρ_D die Standardabweichung der Verteilung des Außendurchmessers D ist.

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

• 0 ≤ (ρ _D / D) ² < 0.3, where ρ _D is the standard deviation of the distribution of the outer diameter D.

The capsules are preferably spherical.

The magnetic color pigments can have 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.

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

The magnetic color pigments can also have features that are disclosed in connection with the method according to the invention for producing optically variable elements (including its developments). In the same way, the method according to the invention for producing optically variable elements can have further process steps that are described in connection with the magnetic color pigments or are necessary in order to produce further features of the magnetic color pigments (including their developments).

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.

A security feature can, for example, be understood as a printing ink that includes a plurality of optically variable elements. Furthermore, the security feature can be designed, for example, as a transfer element or as a film or window with a film cover on the valuable element.

Furthermore, a data carrier, in particular a chip card, identification document and/or document of value (for example a banknote), with a security feature that includes a plurality of the optically variable elements is provided.

• ◯ Einsatz von magnetischen Interferenz-Pigmenten, die hohen Farbkontrast und hohe Brillanz/ Intensität aufweisen.
• ◯ Es sind prinzipiell alle bekannten ColorShift-Aufbauten denkbar.
• ◯ Symmetrischer Pigment-Aufbau:
  • Absorber - Dielektrikum - Reflektor - Magnetische Schicht - Reflektor - Dielektrikum - Absorber oder
  • Absorber - Dielektrikum - Magnetischer Reflektor - Dielektrikum - Absorber oder
  • Magnetischer Absorber - Dielektrikum - Magnetischer Reflektor - Dielektrikum - Magnetischer Absorber
• ◯ Es können zusätzliche Nanostrukturen durch das Prägen der Trennschicht (besonders beim Einsatz von wasserlöslichem UV-Lack oder Heißprägelack) auf das Pigment übertragen werden, wodurch sich zusätzliche Farbeffekte ergeben.

In particular, the following properties of the magnetic color pigments are possible. They can be designed as magnetic interference pigments. They can preferably also have the following details:

• ◯ Use of magnetic interference pigments that have high color contrast and high brilliance/intensity.
• ◯ In principle, all known ColorShift structures are conceivable.
• ◯ Symmetrical pigment structure:
  • Absorber - dielectric - reflector - magnetic layer - reflector - dielectric - absorber or
  • Absorber - dielectric - magnetic reflector - dielectric - absorber or
  • Magnetic absorber - dielectric - magnetic reflector - dielectric - magnetic absorber
• ◯ Additional nanostructures 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.

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

To produce the magnetic pigments, it is possible to use water-soluble or water-swellable UV embossing varnish/hot embossing varnish and various embossing structures, e.g. plateaus or bars, as well as using washing ink to remove the pigments.

The maximum lateral extent 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 extent d is also referred to below as the pigment diameter d.

The outer contour can be chosen so that the following condition is met: 10 µm <= d <=50 µm; preferably 15 µm <= d <= 40 µm; particularly preferably 20 µm <= d <= 30 µm.

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

• 0 <= PDI < 0,2; bevorzugt 0 <= PDI < 0,01; besonders bevorzugt 0 <= PDI < 0,003

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

• 0 <= PDI <0.2; preferably 0 <= PDI <0.01; particularly preferably 0 <= PDI < 0.003

The pigment size distribution has two or three average pigment diameters with the above size distribution (bi- or tri-modal distribution). This can be done e.g. B. achieve well-defined pigments by mixing.

The magnetic pigments are preferably produced in such a way that there is a defined pigment thickness of 0.5 μm to 4 μm, preferably 0.7 μm to 3 μm, particularly preferably 0.8 μm to 2 μm.

• Es ist eine Beschichtung mit Silan- oder Phosphonsäure-Derivaten in nasschemischen Verfahren möglich.

The following additional process steps or features can be specified for pigment coating:

• It is possible to coat with silane or phosphonic acid derivatives using wet chemical processes.

The silanes can be described with the general molecular formula SiXR ₁ R ₂ R ₃ . Where X is an alkyl radical with hydrophobic properties and R ₁ , R ₂ and R ₃ are organic or inorganic radicals. The alkyl radical X consists of 3 <= n =< 16 carbon atoms, preferably of 6 <= n =< 9 carbon atoms. The radicals R ₁ , R ₂ and R ₃ 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 radicals that consist of 1 <= m <= 4 carbon atoms.

The silanes can be described with the general molecular formula SiXYR ₁ R ₂ . Where X and Y are alkyl radicals with hydrophobic properties and R ₁ and R ₂ 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 carbons. The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms. The radicals R ₁ and R ₂ 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 carbons. The alkoxy groups consist of 1 <= m <= 4 carbon atoms.

The silanes can be described with the general molecular formula SiZR ₁ R ₂ R ₃ . Where Z is an organic radical with hydrophobic properties and R ₁ , R ₂ and R ₃ are organic or inorganic radicals. The radicals R ₁ , R ₂ and R ₃ 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 carbons. The alkoxy groups consist of 1 <= m <= 4 carbon atoms. The organic radical Z can be described with the general molecular formula NXA ₁ A ₂ A ₃ A ₄ . Where N represents a primary, secondary, tertiary or quaternary amine, A ₁ , A ₂ , A ₃ and A ₄ correspond to hydrogen atoms or organic alkyl radicals and X represents 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 carbons. The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms.

The silanes can be described with the general molecular formula SiWR ₁ R ₂ R ₃ . Where W is an organic radical with hydrophilic, ionic and non-ionic properties and R ₁ , R ₂ and R ₃ are organic or inorganic radicals. The ionic, organic radical 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 radical 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 applies. The radicals R ₁ , R ₂ and R ₃ 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 carbons. The alkoxy groups consist of 1 <= m <= 4 carbon atoms.

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

The phosphonic acid derivatives can be described with the general molecular formula ZPO(OH) ₂ . Where Z is an organic residue with hydrophobic properties. The organic radical Z can be described with the general molecular formula NXA ₁ A ₂ A ₃ A ₄ . N is a primary, secondary, tertiary or quaternary amine, A ₁ , A ₂ , A ₃ and A ₄ are respectively hydrogen atoms or organic alkyl radicals 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 carbons. The alkyl radicals contain 3 <= n =< 16 carbon atoms, preferably 6 <= n =< 9 carbon atoms.

The phosphonic acid derivatives can be described with the general molecular formula ZPO(OH) ₂ . Where Z is an organic residue with hydrophilic, ionic and non-ionic properties. The ionic, organic radical 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 radical 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 applies.

• - Eisen-Silicium-Legierungen mit den Zusammensetzungen Fe_xSi_y und den Schichtdicken 0,03 bis 0,7 µm
• - Magnetische Schichten aus Eisen (Fe), Cobalt (Co) oder Nickel (Ni) und ihren Legierungen mit den Zusammensetzungen Fe_xNi_y, Fe_xCo_y und Ni_xCo_y
• - Aluminiumhaltige (Al) Legierungen mit den Zusammensetzungen Fe_xAl_y, Co_xAl_y und Ni_xAl_y in den Schichtdicken 0,03 bis 1,0 µm
• - Chromhaltige (Cr) Legierungen und Oxide mit den Zusammensetzungen Fe_xCr_y, Al_xFe_yCr_z, CrO₂, Co_xAl_yCr_z und Ni_xAl_yCr_z in den Schichtdicken 0,03 bis 1,0 µm

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

• - Iron-silicon alloys with the compositions Fe _x Si _y and the layer thicknesses 0.03 to 0.7 µm
• - 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
• - Aluminum-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 µm
• - Chromium-containing (Cr) alloys and oxides with the compositions Fe _x Cr _y , Al _x Fe _y Cr _z , CrO ₂ , Co _x Al _y Cr _z and Ni _x Al _y Cr _z in layer thicknesses of 0.03 to 1.0 µm

• - Vereinzelung über Dissolver
• - Vereinzelung durch Dispergieranlagen, die nach dem Rotor-Stator-Prinzip arbeiten.
• - Vereinzelung durch Einsatz von Dispergieranlagen, die Pigmente durch Vakuum oder Unterdruck vereinzeln.
• - Vereinzelung über ein rotierendes Magnetfelderfolgen, wodurch sich Pigmente die übereinander Konglomerate bilden, vom Magnetfeld induziert auseinander bewegen.
• - Einsatz eines rotierenden Permanentmagneten
• - Einsatz eines mehrpoligen Elektromagneten und elektronische Erzeugung eines Drehfeldes beliebiger Frequenz
• - Vereinzelung über Ultraschall
• - Vorherige Entmagnetisierung mittels abklingenden Magnetfeld und anschließende Vereinzelung durch eine der genannten Methoden
• - Vorherige Entmagnetisierung durch Durchströmen mehrerer elektrisch erzeugter, gekoppelter Drehfelder mit abnehmenden Feldstärken und anschließende Vereinzelung durch eine der genannten Methoden
• - Vorherige Entmagnetisierung durch Erhitzen der Pigmente über ihre Curie-Temperatur und anschließendes Abkühlen. Die Vereinzelung erfolgt mittels einer der genannten Methoden.
• - Kombination der beschriebenen Methoden.

To produce the magnetic pigments, it may be necessary to carry out pigment separation. This can be realized, for example, as follows:

• - Separation via dissolver
• - Separation by dispersion systems that work according to the rotor-stator principle.
• - Separation by using dispersing systems that separate pigments using vacuum or negative pressure.
• - Separation occurs via a rotating magnetic field, whereby pigments that form conglomerates on top of each other move apart induced by the magnetic field.
• - Use of a rotating permanent magnet
• - Use of a multi-pole electromagnet and electronic generation of a rotating field of any frequency
• - Separation via ultrasound
• - Previous demagnetization using a decaying magnetic field and subsequent separation using one of the methods mentioned
• - Previous demagnetization by flowing through several electrically generated, coupled rotating fields with decreasing field strengths and subsequent isolation using one of the methods mentioned
• - Previous demagnetization by heating the pigments above their Curie temperature and then cooling them. Separation is carried out using one of the methods mentioned.
• - Combination of the methods described.

• In dem Herstellungsprozess können drei verschiedene Strukturen zur Erzeugung der Pigmente eingesetzt werden. Jeder der Strukturen setzt sich aus regelmäßigen, geometrischen Substrukturen zusammen. Diese Substrukturen können z.B. rund (beispielsweise kreisförmig, oval, etc.), polygonförmig, (z.B. dreieckig, viereckig, fünfeckig, sechseckig, siebeneckig, achteckig, etc.), sternförmig (z.B. mit 4, 5, 6, 7, 8 oder mehr Zacken) sein. Bevorzugt werden quadratische oder hexagonale Substrukturen verwendet, wobei die hexagonale Substrukturen besonders bevorzugt sind. Die Pigmentgröße ist direkt proportional zur Größe der geometrischen Substrukturen.

Embossing molds can be used to produce the magnetic pigments, which can be produced, for example, as follows:

• In the manufacturing process, three different structures can be used 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, square, pentagonal, hexagonal, heptagonal, octagonal, etc.), star-shaped (e.g. with 4, 5, 6, 7, 8 or more be spikes). 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 type of structure can, for example, include hexagons that touch each other 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 their arrangement, this type of structure is referred to below as a “plateau structure”.

The second type of structure also includes hexagons for illustrative purposes. In this type, the individual polygons also border each other at the edges, but there is a distance between all edges. All hexagons are essentially at the same height. The spacing has a trench-like appearance and has a U, V, semicircular or square profile in cross section. The trench has a depth t of a maximum of 6 µm, or 0.5 < t ≤ 6 µm and a width b of 0.5 < b ≤ 6 µm. The structure type is hereinafter referred to as a “trench structure”.

The third type of structure also includes hexagons for illustration. In this type, the individual polygons also border each other at the edges, but there is a distance between all edges. All hexagons are essentially at the same height. The spacing has a ridge-like appearance and has an inverted U, V, semicircle or square profile in cross section. The comb has a height h _k of a maximum of 6 µm, or 0.5 < h _k ≤ 6 µm and a width b of 0.5 < b ≤ 6 µm. The structure type is referred to below as a “comb structure”.

The (hexagonal) base areas can be slightly offset in height or slightly tilted relative to the base area.

The second and third structure types can be inverse to each other.

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

For structure types two and three, the spacing can be continuous or interrupted. In this way, the efficiency of the predetermined breaking point can be influenced.

• 0° ≤ α < 90°. Bevorzugt sind α < 45° und besonders bevorzugt α < 20°.

In all three structure types, the surfaces are tilted by the angle α. They are therefore not necessarily parallel to the surface and can also be tilted towards each other. The following applies to the angle α:

• 0° ≤ α < 90°. α <45° is preferred and α <20° is particularly preferred.

The three structure types are written lithographically into a polymer matrix, which is then galvanically molded and reproduced. 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.

A water-removable, structurable release coat (UV/hot stamping/wash ink) can be used.

Out of DE 10 2021 004 984 a method for producing pigments of a defined shape and a defined size is known, comprising providing a carrier substrate, coating the carrier substrate with an embossing varnish that hardens using UV radiation and can be removed after UV curing with an aqueous solution, and introducing defined structures into the embossing varnish using embossing technology , which determine the defined shape and size of the pigments to be produced, UV curing of the embossing varnish, coating the embossing varnish with a layer of pigment material, treating the resulting layer structure with an aqueous solution in order to remove the embossing varnish in this way and the for the ready to release individual pigments suitable pigment material layer and to recover the pigments obtainable from the pigment material layer, whereby mechanical stress is optionally exerted on the pigment material layer.

A carrier substrate (e.g. PET film, optionally pre-treated for printing) is optionally treated with corona and coated with an embossing varnish in which the defined structures are embossed. In addition to the embossed predetermined breaking points that define the pigment size and shape, structures that determine the surface structure of the pigments can optionally be embossed. These structures can change the physical and optical properties of the pigments or serve as a forensic feature. The structures can be nanostructures, hologram grids or microstructures. Typically, the height of these surface structures is smaller than that of the embossed predetermined breaking structures so that they do not function as such. The surface structures embossed into the paint are transferred to the pigment.

After or at the same time as the embossing of the embossing varnish, the UV hardening of the UV embossing varnish takes place or the hardening takes place using a heating roller in the case of using a hot embossing varnish. After curing, the embossed lacquer layer can be removed with water (water-soluble or water-swellable). It is very advantageous for water removability if the embossing lacquer layer is not completely cured.

The degree of curing of the UV embossing lacquer layer in the embossing process could be influenced using the following parameters: Type of UV emitter (conventional (iron-doped) mercury medium-pressure emitter or UV LED emitter), amount of suitable photoinitiators (wavelength-dependent), temperature input during the embossing process, addition of chain carriers.

Suitable raw materials for the UV embossing varnish are prepolymers and/or reactive diluents, such as polyethylene glycol diacrylate, ethoxylated trimethylolpropane triacrylate, acryloylmorpholine (see, for example, the 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 optionally Additives.

• ◯ 75-90% Photomer 4159 (IGM)
• ◯ 5-20% ACMO
• ◯ 0,5-3% Polysiloxan-Tensid
• ◯ 2-7% Omnirad 2100 oder
• ◯ 75-93% Photomer 4056 (IGM)
• ◯ 5-20 % Photomer 4054
• ◯ 2-7% Omnirad 2100

Recipe examples for a water-swellable UV embossing varnish:

• ◯ 75-90% Photomer 4159 (IGM)
• ◯ 5-20% ACMO
• ◯ 0.5-3% polysiloxane surfactant
• ◯ 2-7% Omnirad 2100 or
• ◯ 75-93% Photomer 4056 (IGM)
• ◯ 5-20% Photomer 4054
• ◯ 2-7% Omnirad 2100

• Rezeptur z.B:
  • ◯ 95 % Laromer 8983 + 5 % Irgacure 819 DW
  • ◯ 75 % Laromer 8983 + 20 % Laromer 9005 + 5 % Irgacure 819 DW

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

• Recipe e.g.:
  • ◯ 95% Laromer 8983 + 5% Irgacure 819 DW
  • ◯ 75% Laromer 8983 + 20% Laromer 9005 + 5% Irgacure 819 DW

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 carried out in the thermoplastics before optional UV curing.

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 detachment of the well-formed pigments in the later washing process or, in the case of the insoluble UV varnish, makes it possible.

• Nach der Härtung des Prägelacks wird die gehärtete Prägelackschicht metallisiert. Die Pigmentmaterialschicht ist eine optisch wirksame Funktionsschicht mit zusätzlicher magnetischer Schicht, vorzugsweise ein farbkippendes Dünnschichtsystem mit der Schichtenfolge Absorber/ Dielektrikum/ Reflektor/ magnetische Schicht/ Reflektor/ Dielektrikum/ Absorber oder Absorber/Dielektrikum/Magnetischer Reflektor/Dielektrikum/ Absorber. Das Dünnschichtsystem kann dabei durch Elektronenstrahlverdampfer oder andere gängige PVD-Systeme aufgebracht werden.

Metallization can be carried out as follows:

• After the embossing varnish has hardened, the hardened embossing varnish 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 evaporators or other common PVD systems.

If washing ink is used, the metallization takes place after the embossing varnish has been printed with the corresponding washing ink.

• In einem Rolle-zu-Rolle Prozess wird das beschichtete bzw. metallisierte Substrat durch ein (gegebenenfalls heißes) Wasserbad gefahren und somit (gegebenenfalls mithilfe mechanischer Prozesse, wie Bürsten im Wasserbad oder über eine Rolle vor dem Wasserbad) die mit Wasser ablösbare Prägelackschicht aufgelöst oder gequollen, oder die Schicht der Waschfarbe an- oder aufgelöst, sodass die aufgedampfte Metallisierung gewissermaßen abgesprengt wird und die wohlgeformten, plättchenförmigen Effektpigmente gewonnen werden. Wenn der Prägelack wasserlöslich ist, werden die Pigmente abgetrennt (z.B. durch Dekantieren) und gewaschen. Wenn der Prägelack wasserquellbar ist, werden die Pigmente von gegebenenfalls im Wasser schwimmenden Prägelackstücken, die sich vom Trägersubstrat abgelöst haben, abgetrennt (z.B. durch Dekantieren, oder evtl. durch Abtrennen aufgrund von magnetischen Eigenschaften der Pigmente). Das Ablösen erfolgt mit Wasser, vorzugsweise in basischer Wasserlösung (Verseifung und Rückbildung der Carbanionen). Die Basizität kann über NaOH, Ammoniak, Amine und in wässriger Lösung basisch reagierende Salze, wie beispielsweise Alkalicarbonate erzeugt werden.

Optional washing can be done as follows:

• In a roll-to-roll process, the coated or metallized substrate is passed through a (possibly hot) water bath and thus (if necessary with the help of mechanical processes, such as brushing in the water bath or using a roller in front of the water bath) the water-removable embossing varnish layer is dissolved or swollen, or the layer of washing color dissolves or dissolves, so that the vapor-deposited metallization is, so to speak, blasted off and the well-formed, platelet-shaped effect pigments are obtained. If the embossing varnish is water-soluble, the pigments are separated (e.g. by decanting) and washed. If the embossing varnish is water-swellable, the pigments are separated from any pieces of embossing varnish floating in the water that have detached from the carrier substrate (for example by decanting, or possibly by separating due to the magnetic properties of the pigments). The removal is carried out with water, preferably in a basic water solution (saponification and regression of the carbanions). The basicity can be generated via NaOH, ammonia, amines and salts that react basicly in aqueous solution, such as alkali metal 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, optionally pre-printed), the trench structures are embossed and hardened. This paint has properties that reduce the adhesion of the metallization. Hot stamping varnishes with corresponding properties are also conceivable for this. This film is vapor-coated with one of the layer structures mentioned using the PVD process.
A second carrier film (e.g. PET, optionally pre-treated for printing) is printed with a preferably water-soluble, adhesive varnish. Both rolls are laminated on top of each other so that the print layers lie on top of each other. After a rest period of up to seven days, the films are separated. The raised, metallized hexagons are transferred to the sticky film. Individual pigments are obtained by washing the preferably water-soluble, adhesive varnish.

Drainage 1

Optionally, a dewatering step can be implemented before the surface treatment of the pigments if the pigment content in the washing medium is very low (see point “Washing”) in order to concentrate the pigment in the washing medium. This can be accomplished, for example, with a decanter centrifuge or a chamber filter press. A filter cake or a pigment slurry with a solids content of greater than 5% and less than 95% can be achieved, which can be separated from the filtrate.

Surface treatment

The surface treatment can be carried out using wet chemical processes.

The dewatered, moist pigments are suspended, for example, in a solvent with the weight proportion w, which can be between 5 and 75%. The solvent is liquid in the application range between 5 and 95 °C and can be either organic or inorganic. Suitable solvents include water, lower alcohols up to six carbon atoms, alkanes from five carbon atoms, toluene, xylenes, organic carbonates, DMSO, ketones up to eight carbon atoms, cyclic and acyclic ethers from two carbon atoms, aldehydes up to six carbon atoms and carboxylic acids up to six carbon atoms.

The pH value is adjusted by adding an acid or base that is soluble in the solvent. The acids include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, carbonic acid, citric acid, methanoic acid, ethanoic acid, oxalic acid, succinic acid or tartaric acid. The bases include ammonia and its organic derivatives from the group of amines, where one, two or three hydrogen atoms of ammonia can be substituted by organic radicals, and aqueous solutions of ammonia, lithium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide. pH-changing salts made from the acids and bases mentioned can also be used. The desired pH value is between pH = 2 and pH = 11. The acid or base or salt used must be miscible with the solvent in the amount used and must not enter into any reactions, side reactions or form separate phases.

The reaction mixture is completed by adding an organic silane or phosphonic acid derivative. Both classes of compounds are intended to improve surface properties and generally protect the pigments from chemical attacks. 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. The 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.

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%.

Drainage 2

Before the final drying of the pigments, the reaction reagents of the surface treatment must be separated from the pigment. Here, the pigment is filtered again using 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. A filter cake or a pigment slurry with a solids content of greater than 5% and less than 95% can be achieved, which can be separated from the filtrate.

drying

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

sighting

Alternatively, pigment fragments or pigment composites arise in the pigment production process, e.g. due to mechanical stress or sticking of the pigment during surface treatment, dewatering or drying. In order to sift the upper and lower grains, i.e. to separate them from pigments of the desired size, cyclone sifters and sieve systems can be used.

Capsules - definition and production

Definition/goals of encapsulation

• - Das Pigment wird in einem flüssigen Kern beweglich, in einer festen Hülle verkapselt.
• - Das Pigment schwimmt im flüssigen (bevorzugt ölhaltigen) Kern
• - Das Pigment wird mit chemischen Mitteln im Zentrum gehalten
• - Das Pigment wird von der Kapselwand abgestoßen
• - Die Kapsel enthält genau ein Pigment oder nur wenige Pigmente

Core-shell system:

• - The pigment becomes mobile in a liquid core and encapsulated in a solid shell.
• - The pigment floats in the liquid (preferably oily) core
• - The pigment is held in the center using chemical means
• - The pigment is expelled from the capsule wall
• - The capsule contains exactly one pigment or only a few pigments

From the capsule outer diameter D and the thickness of the capsule shell h, the diameter D' for the liquid capsule core results in: D' = D - 2h (thus corresponds to the inside diameter of the capsule shell).

The liquid capsule core is only slightly larger than the pigment: $$\begin{array}{l}1<\left(\text{D}-2\text{H}\right)/\text{d}<\mathrm{2.0,}\text{preferred 1}\text{,05}<\left(\text{D}-2\text{H}\right)/\text{d}<1.5\text{particularly preferred}\\ \text{1}\text{,1}<\left(\text{D}-2\text{H}\right)/\text{d}<1.4\end{array}$$

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

This fluctuation can be defined, for example, via the target value of the capsule outer diameter D and/or the polydispersity index (PDI'): $$\begin{array}{l}15\mathrm{\mu }\text{m}<=\text{D}<=100\mathrm{\mu }\text{m}+/-10\mathrm{\mu }\text{m; preferred}15\mathrm{\mu }\text{m}<=\text{D}<=50\mathrm{\mu }\text{m}+/-5\mathrm{\mu }\text{m;}\\ \text{particularly preferred}24\mathrm{\mu }\text{m}<=\text{D}<=35\mathrm{\mu }\text{m}+/-3\mathrm{\mu }\text{m}\end{array}$$

Capsule size distribution characterized as PDI' with PDI' = (σ _D /D) ² , where σ _D is the standard deviation of the capsule outside diameter distribution: $$\begin{array}{l}0<=\text{PDI}\text{'}<0.3;\text{preferred}0<=\text{PDI}\text{'}<0.2;\\ \text{particularly preferred}0<=\text{PDI}\text{'}<0.1\end{array}$$

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

Each capsule contains only a few pigments, preferably less than 6, 5, 4 or 2 pigments. One capsule particularly preferably contains exactly 1 pigment.

• ◯ Mikrofluidik
  • - Einsatz von zwei oder mehr Fluiden in einem einstufigen Prozess
  • - Einsatz von zwei oder mehr Fluiden in einem mehrstufigen Prozess
  • - Step-Emulsification-Reaktoren
  • - Co-Flow-Reaktoren
  • - Flow-Focusing-Reaktoren
  • - Microchannel-Emulsification
• ◯ Co-Extrusion
  • - Einsatz monozentrischen oder konzentrischen Düsen
  • - Einsatz von zwei oder mehr Fluiden in einem einstufigen Prozess
  • - Einsatz von zwei oder mehr Fluiden in einem mehrstufigen Prozess
  • - Tropfenbildung mittels Vibration
  • - Tropfenbildung über periodische Druckschwankungen der kontinuierlichen/ äußeren Phase
• • Beschreibung der Kapsel-Herstellung durch Mikrofluidik

Encapsulation processes are used that promote an extremely narrow size distribution of the capsules. The following methods can be used, for example:

• ◯ Microfluidics
  • - Use of two or more fluids in a one-step process
  • - Use of two or more fluids in a multi-stage process
  • - Step emulsification reactors
  • - Co-flow reactors
  • - Flow focusing reactors
  • - Microchannel emulsification
• ◯ Co-extrusion
  • - Use of monocentric or concentric nozzles
  • - Use of two or more fluids in a one-step process
  • - Use of two or more fluids in a multi-stage process
  • - Drop formation using vibration
  • - Drop formation via periodic pressure fluctuations in the continuous/outer phase
• • Description of capsule production using microfluidics

The capsules can be produced using microfluidics. Microfluidics is able to safely handle the small volume of liquid within the capsule. Typically, volumes in the range of 10 ^-9 to 10 ^-18 liters are processed in microfluidics. Larger volumes can also be used and processed through numbering-up.

Microdrops are required to produce the microcapsules. Microdroplets can be created by T- and Y-shaped cross-flow geometries, co-flow geometries, flow-focusing geometries, microchannel emulsification geometry and step emulsification geometries. Combinations of the basic geometries mentioned have also proven to be suitable. Preferred geometries must be able to process at least two fluids. These fluids must not be miscible and may differ in their polarities, viscosities and compositions. The diameters of the structures are in the Magnitude of the required drop sizes, d < 100 µm. Inflows and outflows of all fluids can be larger. In addition, the structures must be able to achieve the required polydispersity index values.

In the simplest structure, this methodology requires two different fluids for the formation of microdrops or microcapsules. One fluid A represents the dispersive phase to be dripped. The other fluid is the continuous phase B. The disperse phase A contains the pigments, additives and dissolved, crosslinkable polymers. Overall, the disperse phase has a non-polar, oleophilic character. The continuous phase has a more hydrophilic character and, in addition to additives, also contains a dissolved crosslinker. All chemicals that change the interface properties, rheological properties, density or optical properties are summarized as additives. The crosslinked polymer can come from the group of polyurethanes, polyacrylates, polymethacrylates, polyamides, polyacrylonitriles, polycarbonates, melamine resins or polyesters. The polymer may only be soluble in the dispersive phase B. The crosslinker, on the other hand, may only be soluble in the continuous phase A. During the dripping process, droplets form, which is caused by the different hydrophilic and lipophilic character of the fluids and the attempt to minimize surface area. By using the additives, the stability of the droplets formed is significantly increased. At the interface between the discontinuous and continuous phase, a reaction occurs between the crosslinkable polymer and the crosslinker. Depending on the reaction time, a polymer skin or wall is formed. By varying the fluid pressures or volume flows, the amount of capsules formed and their diameter can be directly influenced.

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

Droplet and capsule formation can also occur by exchanging the two phases and their properties. Care must be taken in the selection of materials and equipment.

The separation of filled and empty capsules can be done using a static or dynamic, magnetic or electric field. Separation and sorting using the Lorentz force is possible. Another option for separation and classification is the use of helical structures. These structures enable the capsules to be separated due to their different flow properties.

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

In more complex encapsulation arrangements, three or more fluids may be used. There is at least one pigment-containing, disperse phase, a likewise disperse phase that later forms the capsule shell and a continuous phase that separates the formed drops from one another. 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.

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

Droplet and capsule formation can also occur by exchanging the two phases and their properties. Care must be taken in the selection of materials and equipment. In order to achieve a high filling rate of the capsules 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 supply 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 where the droplets are formed. The control frequency of the minimum two-phase electromagnet is varied according to the conveying speed to be set.

The pressure p, which is used to promote the continuous phase, can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. Through appropriate placement and design selection of the microfluidic structures, the continuous phase can be dispensed with and a beaker or other container filled with the continuous phase can be used. This container acts as part of the drop formation and at the same time as a way to store, store or temporarily store formed drops or capsules. Its use as a hardening bath is also conceivable. The continuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver or a pump.

The pressure p, which is used to promote the disperse 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.

All liquids that are used as a 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.

All liquids that are 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 which is above 105 °C, preferably above 150 °C and particularly preferably above 250 °C.

All liquids that are 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 by adding rheological additives, temperature changes or partial polymerization is possible. It is also possible to reversibly increase and/or reduce the viscosity, for example through guar gum and its derivatives and with the help of temperature, time and pH value changes.

All liquids that are used as a disperse or continuous phase must have a density between 500 and 5000 kg/m ³ , preferably between 800 and 3400 kg/m ³ . This density can be changed by diluting or concentrating. A change in density by changing the temperature or pH value 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.

The liquids that are used as a disperse or continuous phase can be organic, inorganic and mixed in nature. Mixtures of organic and inorganic liquids are conceivable in every chemical-physically possible ratio. The substances are defined in more detail below.

In a narrower sense, organic liquids include natural and artificial triglycerides and other esters of saturated and mono- or polyunsaturated fatty acids. This also includes triglycerides and esters, which consist of saturated and mono- or polyunsaturated fatty acids, and mixtures of triglycerides and esters, which consist 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 glycerol. The esterification of the alcohol or organic acid does not have to be complete. Sunflower oil, soybean oil and peanut oil should be mentioned here.

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

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

Mixed and/or pure, aliphatic and/or aromatic, branched and/or unbranched and n- and/or iso-hydrocarbons and their mixtures can be used as further organic liquids. Examples include white spirits.

Water is an inorganic liquid.

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

The 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 to be liquids of mixed nature. Silicone oils are also included in this group.

Description of capsule production by co-extrusion

The process is divided into extrusion and co-extrusion. The difference lies in the number of liquids used. Only a liquid is used during extrusion. The description of the materials used and process parameters follows the description of the manufacturing process.

There are basically two methods for forming the drops. The first method is to vibrate a nozzle by stimulating it. The amplitude and frequency have a significant influence on the formation of drops. The prediction can be made, for example, via the Rayleigh instability. This method is called vibration technique. Drop formation through targeted pulsation of the liquid is conceivable. The second method is the targeted tearing off of a drop by a fluid flowing past. This can be either a liquid or a gas, which is why the method is called AirJet or Flow Focusing. One influencing factor here is, for example, the relationship between the flow velocities. Both methods enable a very narrow size distribution of the drops.

During extrusion, a liquid is dripped using the methods mentioned. In addition to the pigment, this also contains surface additives and a reactive prepolymer. The prepolymer can be crosslinked, for example, by IR/UV radiation, with a gas or a curing bath. Curing can then take place in free fall using IR/UV radiation or gas or in the curing bath using a crosslinking component, UV radiation or temperature changes. The hardening bath and the pigment-containing liquid must not be miscible. The curing time determines the hardness and thickness of the capsule wall.

In co-extrusion, two or more liquids flow through a concentric nozzle, forming a multi-layered fluid jet. The liquids are not miscible. Drop formation occurs either through the outermost liquid flowing past, through pulsation of one or more liquids, or through 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 take place through interfacial polymerization at the interface of continuous and discontinuous phases. The prepolymer is in one phase and the crosslinker is in the other. Another way is that the continuous phase is 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, disperse 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 process are also possible here.

The capsules produced in this way can also be cross-linked or surface-treated.

The finished capsules are dried.

In the final step, the capsules are sorted according to functionality and dispersity. The functional capsules can be separated using a magnetic or electromagnetic field. The desired capsule sizes can be separated by sieve or flow classification.

The nozzle vibrates at a frequency f between 0 and 20,000 Hz and preferably between 500 and 5000 Hz. The vibration follows a sine wave.

The flow ratio of the continuous and discontinuous phases to one another is <2:1, preferably <5:1 and particularly preferably <10:1.

The surface additives used can be nonionic, anionic, cationic or amphoteric surfactants. Non-ionic surfactants include polyalcohols, ethers and their combination in the form of ethoxylates. The anionic and cationic surfactants used include carboxylates, sulfonates such as sodium dodecyl benzyl sulfonate, sulfates such as sodium dodecyl sulfate and quaternary ammonium compounds. Among the zwitterionic surfactants, betaines such as cocoamidopropyl betaine and sultaine should be mentioned.

The pressure p, which is used to promote the continuous phase, can be between 0 and 7000 mbar, preferably between 0 and 2000 mbar, particularly preferably between 0 and 1500 mbar. By appropriate placement of the microfluidic structures, the continuous phase can be dispensed with and a beaker or other container filled with the continuous phase can be used. This container acts as part of the drop formation and at the same time as a way to store, store or temporarily store formed drops or capsules. Its use as a hardening bath is also conceivable. The continuous phase is continuously homogenized or circulated during the process by a stirrer, a dissolver or a pump.

The pressure p, which is used to promote the disperse 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.

All liquids that are used as a 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.

All liquids that are 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 which is above 105 °C, preferably above 150 °C and particularly preferably above 250 °C.

All liquids that are 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 by adding rheological additives, temperature changes or partial polymerization is possible. It is also possible to reversibly increase and/or reduce the viscosity, for example through guar gum and its derivatives and with the help of temperature, time and pH value changes.

All liquids that are used as a disperse or continuous phase must have a density between 500 and 5000 kg/m ³ , preferably between 800 and 3400 kg/m ³ . This density can be changed by diluting or concentrating. A change in density by changing the temperature or pH value 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.

The liquids that are used as a disperse or continuous phase can be organic, inorganic and mixed in nature. Mixtures of organic and inorganic liquids are conceivable in every chemical-physically possible ratio. The substances are defined in more detail below.

In a narrower sense, organic liquids include natural and artificial triglycerides and other esters of saturated and mono- or polyunsaturated fatty acids. This also includes triglycerides and esters, which consist of saturated and mono- or polyunsaturated fatty acids, and mixtures of triglycerides and esters, which consist 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 multiple alcohols and glycerol. The esterification of the alcohol or organic acid does not have to be complete. Sunflower oil, soybean oil and peanut oil should be mentioned here.

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

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

Mixed and/or pure, aliphatic and/or aromatic, branched and/or unbranched and n- and/or iso-hydrocarbons and their mixtures can be used as further organic liquids. Examples include white spirits.

Water is an inorganic liquid.

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

The 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 to be liquids of mixed nature. Silicone oils are also included in this group.

The temperature of the curing bath can be between -15 and +60 °C, preferably between 0 and 45 °C and particularly preferably between 15 and 35 °C.

Isocyanates such as TDI and MDI, glutaraldehyde and formaldehyde can be used as the curing component in the curing bath. The use of dicarboxylic acids is also conceivable. Post-curing may be carried out using the same chemicals.

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

The curing time can be up to 48 hours, preferably <24 hours, most preferably <1 hour.

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

• • Beschreibung sonstiger Verkapselungsverfahren für enge monomodale Verteilung

If the capsule wall is formed by 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 very preferably 250 ° C.

• • Description of other encapsulation methods for narrow monomodal distribution

Further methods are named below that are generally suitable for the formation of drops with a narrow size distribution.

Electrostatic dripping: By applying a voltage to the liquid to be dripped and the liquid to be absorbed, an electrostatic force is created. This helps to overcome the adhesion force. The process is suitable for producing drops with sizes between 300 µm and 5 mm in very narrow size distributions. In experiments, the droplet size was reduced to a diameter of around 50 µm. The hardening of the pigment-containing disperse phase would again take place using an immiscible hardening bath or during free fall with IR/UV radiation, a gas and/or a combination. Hardening by changing temperature is also possible.

Jet Cutter Process: In the Jet Cutter process, a laminar jet of liquid is forced through a nozzle at high speed. Directly below the nozzle there is a rotating disk that uses thin wires to cut cylindrical segments from the jet. The surface tension then causes spherical drops to be formed from the cylinders. Droplet generation is based on the mechanical impact of the liquid jet on the cutting wire. The impact causes cutting, resulting in the cylindrical section and cutting loss. In a first approximation, the cutting loss can be assumed to be a cylinder with the height of the wire diameter. This cylinder is thrown outwards where it is collected and recovered. Only the mechanical cut and surface tension are responsible for the formation of drops. 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 have a narrow size distribution To maintain the flow, the nozzle must flow evenly. The pumps used must therefore work 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 and 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, the pigment-containing, disperse phase can be hardened either in the gas phase using IR/UV radiation, a gas and/or in an immiscible hardening bath. Hardening by changing temperature is also possible.

Hydrophobization can advantageously be used on the pigments in order to significantly improve stability and separation in non-polar carrier liquids.

Furthermore, tests have shown that the settling stability of dispersions improves significantly with the alkyl residue length of the surface treatments in oils and paraffin oils. The best results are obtained with C8 and C16 alkyl radicals.

It has been shown that monodisperse capsules do not represent an obstacle. Neither with a liquid core nor completely hardened. The targeted coating/encapsulation of solid particles is also possible. There are works from microbiology in which human egg cells (d = 200 µm) and liver cells (d = 70 µm) are individually encapsulated. In technology, spherical nanoparticles are packed into 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 (± a power of ten) can be packed into monodisperse capsules. The new thing is that flat particles that are approximately two-dimensional are encapsulated. Biological cells and nanoparticles, on the other hand, are approximately spherical.

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

Printing ink and printing - definition and production

• ◯ Es wird die dichteste Kugelpackung ein- und zweilagig angestrebt
• ◯ > 80 % der Kapseln sind funktionsfähig
• ◯ Bevorzugt: > 90 % der Kapseln sind funktionsfähig
• ◯ Magnetsortierung der Kapseln vor der Farbherstellung
  • • Trocknung oxidativ oder Strahlungsinduziert
• ◯ UV-Trocknung
• ◯ Elektronenstrahl-Trocknung
• ◯ Vernetzung zwischen Kapselmaterial und Bindemittel vorteilhaft
  • • Beständigkeit der Farbschicht und der Kapseln gegenüber den üblichen chemischen und physikalischen Banknoten Beständigkeitstests
  • • Einbringung in Hybrid-Fenster oder im klassischen BN-Fenster (Euro)
  • • Druckschichtdicke < 100 µm, bevorzugt < 60 µm, besonders bevorzugt <= 40 µm
  • • Druckverfahren: Tiefdruck, Stichtiefdruck, Siebdruck, bevorzugt Siebdruck

High area coverage of functional capsules (optically variable elements according to the invention):

• ◯ The densest packing of spheres in one and two layers is sought
• ◯ > 80% of the capsules are functional
• ◯ Preferred: > 90% of the capsules are functional
• ◯ Magnetic sorting of the capsules before color production
  • • Drying is oxidative or radiation-induced
• ◯ UV drying
• ◯ Electron beam drying
• ◯ Networking between capsule material and binder is advantageous
  • • Resistance of the ink layer and the capsules to the usual chemical and physical banknote resistance tests
  • • Installation in hybrid windows or in the classic BN window (Euro)
  • • Print layer thickness <100 µm, preferably <60 µm, particularly preferably <= 40 µm
  • • Printing process: gravure printing, intaglio printing, screen printing, preferably screen printing

Design - Easier recognition of the security feature

• • Kontrasterhöhung durch
  • - Dunklen oder schwarzen Untergrunddruck
  • - Einfärbung des Bindemittels in einer Kippfarbe des ColorShift-Pigmentes
  • - Einfärbung des Untergrunddrucks in einer Kippfarbe des ColorShift-Pigmentes
• • Verstärkung des Erkennungseffektes
  • - Vervollständigung einer zuvor nur teilweise erkennbaren Information, z.B. eines Währungssymbols oder einer Wertzahl
  • - Auftauchen einer verdeckten Information, z.B. durch geteilten Druck von feststehenden Kapseln oder einer sehr ähnlichen Farbe und funktionalen Kapseln. Die verdeckte Information wird anschließen durch die Bewegung eines Magneten unter dem Sicherheitselement sichtbar gemacht, indem sich ein dynamischer Farbeffekt der funktionalen Kapseln vom feststehenden Bereich optisch differenziert.

A clever design makes it easier to recognize and verify the security feature, thereby increasing security.

• • Contrast increase through
  • - Dark or black background print
  • - Coloring the binder in a color shift of the ColorShift pigment
  • - Coloring the background print in a tipping color of the ColorShift pigment
• • Enhancement of the recognition effect
  • - Completion of previously only partially recognizable information, e.g. a currency symbol or a value number
  • - Emergence of hidden information, e.g. through split printing of fixed capsules or a very similar color and functional capsules. The hidden information is then made visible by moving a magnet under the security element, with a dynamic color effect of the functional capsules visually differentiating it from the fixed area.

The capsules and color systems according to the invention can also be used to protect branded products against product piracy and to detect the authenticity of ID documents.

• 1 ein Wertdokument 4 mit einem Sicherheitsmerkmal 2;
• 2 eine vergrößerte Teilschnittansicht entlang der Schnittlinie A-A in 1;
• 3 die vergrößerte Teilschnittansicht gemäß 2 mit angelegtem lokalem Magnetfeld;
• 4 die vergrößerte Teilschnittansicht gemäß 2 mit angelegtem lokalem Magnetfeld, das eine andere Orientierung aufweist als in 3;
• 5 ein Ablaufdiagramm zur Erläuterung der Erzeugung des Sicherheitsmerkmals 2 in 1;
• 6 ein Ablaufdiagramm zur Erläuterung des Verfahrensabschnitts G1 in 5;
• 7 ein Ablaufdiagramm zur Erläuterung des Verfahrensabschnitts G3 in 5, und
• 8 ein Ablaufdiagramm zur Erläuterung des Verfahrensabschnitts G5 in 5.

The invention will be explained in more detail below using exemplary embodiments with reference to the accompanying drawings, which also reveal features essential to the invention. These embodiments are for illustrative purposes only and are not to be construed as limiting. For example, a description of an embodiment including a plurality of elements or components should not be construed to mean that all of these elements or components are necessary for implementation. Rather, other 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 specified. Modifications and variations described for one of the embodiments may also be applicable to other embodiments. To avoid repetition, the same or corresponding elements in different figures are designated with the same reference numerals and are not explained more than once. Show in the figures:

• 1 a valuable document 4 with a security feature 2;
• 2 an enlarged partial sectional view along section line AA in 1 ;
• 3 the enlarged partial sectional view according to 2 with applied local magnetic field;
• 4 the enlarged partial sectional view according to 2 with an applied local magnetic field that has a different orientation than in 3 ;
• 5 a flowchart to explain the generation of the security feature 2 in 1 ;
• 6 a flowchart to explain the process section G1 in 5 ;
• 7 a flowchart to explain the process section G3 in 5 , and
• 8th a flowchart to explain the process section G5 in 5 .

At the in 1 In the embodiment shown, the optically variable elements 1 according to the invention are provided as part of a printing ink as a security feature 2 on a top side 3 of a document of value 4 (such as a bank note). To better explain the invention, the optically variable elements 1 are not true to scale but are clearly enlarged and shown schematically.

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

Since the capsule 5 is spherical with an outer diameter D and an inner diameter D 'that is larger than the maximum lateral extent d of the magnetic color pigment 8, the magnetic color pigment 8 is freely rotatable in the capsule 5. Like the enlarged sectional view in 2 As can be seen, the magnetic color pigments 8 are aligned parallel to the top 3 or randomly distributed without the presence of a local external magnetic field, so that a viewer, who looks at the top 3, perceives the color of the magnetic color pigments 8 in a first form. If a local external magnetic field is now created using the in 3 Schematically shown magnets 9 are provided in the area of the security feature 2, the magnetic color pigments 8 will align themselves with the magnetic field lines (shown schematically as dotted lines), as in 3 is shown. In this case, a viewer who looks at the top 3 of the document of value 4 will essentially perceive the area of the top 3 below the security feature 1.

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

This means that any angle of inclination of the magnetic color pigments 8 relative to the top 3 can be set by aligning the local magnetic field. If the magnetic color pigments 8 not only have a simple color layer, but, for example, a color-shifting coating (for example a corresponding interference structure with, for example, a reflector dielectric, partially reflective cover layer), these color-shifting effects can be achieved by changing the angle at which the magnetic color pigments 8 are oriented towards the top 3, are generated for a viewer of the top 3. By moving the magnet accordingly, dynamic, high-contrast color effects can be observed, which underline the special security character of the new security element.

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

The maximum lateral extent 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 extent d is relatively small. Thus, a polydispersity index PDI = (σ _d /d) ² , where σ _d 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 be 0.003.

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

The liquid core 7 can in particular be a core that preferably contains oil. Furthermore, the magnetic color pigment 8 and the capsule wall are designed such that the magnetic color pigment 8 is repelled from the capsule wall. The inner capsule diameter D' results from the outer diameter D of the capsule 5 minus 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.

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 outer diameter of the capsule D can be greater than or equal to 24 µm and less than or equal to 35 µm with a tolerance of +/- 3 µm.

A polydispersity index PDI' = (σ _D / D) ² for the outer diameter D of the capsules 5, where σ _D is the standard deviation of the capsule outer diameter distribution, can satisfy the following condition: 0 ≤ PDI'< 0.3, preferably 0 ≤ PDI'< 0.2 and particularly preferably 0 ≤ PDI'< 0.1.

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

The method steps for producing the optically variable elements 1 and for producing the security feature 2 are described below as examples.

In order to produce the optically variable elements 1, in a process section G1 ( 5 ) the magnetic color pigments 8 are produced.

In a process section G2, the magnetic color pigments 8 produced in this way are dispersed in the core liquid for the liquid cores 7.

In a subsequent process section G3, the magnetic color pigments 8 dispersed in the core liquid are then encapsulated.

In process section G4, the optically variable elements 1 produced in this way are then sorted and/or quality checked.

In order to be able to produce the desired security element 2, a corresponding printing ink is generated with the optically variable elements 1 in a subsequent process section G5.

In process section G6, the desired security feature 2 is then printed on the top side 3 of the valuable document 4 using the printing ink from process section G5.

The process sections G1, G3 and G5 are described in more detail below. In process section G1, an embossing mold for producing the color pigments 8 is produced in a first step S1.

In step S2, a lacquer is applied, which is then embossed in step S3 with the embossing mold from step S1. In an optional step S4, a wash color can be applied. In step S5, metallization is carried out, followed by a washing step (step S6) and a first dewatering (step S7). This is then followed by surface treatment (step S8) and dewatering including drying (step S9).

For the encapsulation of the pigments according to process section G3, individual transport of the pigments in the core liquid can be carried out in a step S10. In step S11, the pigments in the core center are stabilized.

In step S12, droplet and interface formation occurs, followed by capsule formation/interface polymerization in step S13.

To produce the printing ink, the capsules 5 are dispersed in a binder (step S14). This is then followed by a color formulation with a drying system (for example oxidative, UV, radiation-crosslinking, etc.) in step S15. In step S16, quality assurance can then be carried out, such as. B. a rheological measurement.

Reference symbol list

1

optically variable element

2

Security feature

3

Top

4

document of value

5

capsule

6

solid cover

7

liquid core

8th

magnetic color pigment

9

magnet

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102021004984 [0060]
• EP 3230795 B1 [0064]

Claims (16)

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 flat, have the same outer contour with a maximum lateral extent d and meet the following condition A: 0 ≤ (ρ _d / d) ² <0.2, where ρ _d 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 in such a way 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 can therefore be magnetically aligned, are present. Procedure according to Claim 1 , in which one to a maximum of five magnetic color pigments (8) are encapsulated in each capsule (5) in the encapsulation step. Procedure according to Claim 1 or 2 , in which in the encapsulation step the capsules (5) are produced in such a way that the shell (6) of the capsules (5) has an outer diameter D and the following condition B is met: 0 ≤ (ρ _D / D) ² < 0.3 , where ρ _D is the standard deviation of the distribution of the outside diameter D. Method according to one of the above claims, in which in the pigment production step the magnetic color pigments (8) are provided with an optically variable thin-film system. Method according to one of the above claims, in which the pigment production step and the encapsulation step are carried out so that the following condition C is satisfied: 1 < D'/d < 2.0, where D' is the inner diameter of the capsule (5). Method according to one of the above claims, in which in the pigment production step the magnetic color pigments (8) have a thickness of greater than or equal to 0.5 µm and less than or equal to 4 µm and a maximum lateral extent d of greater than or equal to 0.5 µm and less or equal to 50 µm. Method according to one of the above claims, in which, in the pigment production step, the magnetic color pigments (8) are produced with a monodisperse pigment size distribution in which there is an average value for the maximum lateral extent d that meets condition A for all magnetic color pigments (8). Procedure according to one of the Claims 1 until 6 , in which, in the pigment production step, the magnetic color pigments (8) are produced with a bi- or tri-modal pigment size distribution, in which there are two or three mean values for the maximum lateral expansion d for the magnetic color pigments (8) that fulfill condition A. Optically variable elements for producing a printing ink and/or a security feature, the optically variable elements (1) each comprising a capsule (5) with a solid shell (6) and a liquid core (7), in each capsule (5) at least one magnetic color pigment (8) floats in the liquid core and can therefore be magnetically aligned, the magnetic color pigments (8) being flat, having the same outer contour with a maximum lateral extent d and being produced in such a way that the following condition A is fulfilled : 0 :9 (ρ _d / d) ² < 0.2, where ρ _d is the standard deviation of the distribution of the maximum lateral extent d. Optically variable elements Claim 9 , with one to a maximum of five magnetic color pigments (8) being encapsulated in a capsule (5). Optically variable elements Claim 9 or 10 , wherein the capsules (5) are manufactured in such a way that the shell (6) of the capsules (5) has an outer diameter D and the following condition B is met: 0 ≤ (ρ _D / D) ² < 0.3, where ρ _D is the standard deviation of the distribution of the outside diameter D. Optically variable elements according to one of the Claims 9 until 11 , wherein the magnetic color pigments (8) have an optically variable thin-film system. Optically variable elements according to one of the Claims 9 until 12 , whereby the following condition C is met: 1 <D' / d < 2.0, where D' is the inner diameter of the capsule (5). Optically variable elements according to one of the Claims 9 until 13 , wherein the magnetic color pigments (8) have a thickness of greater than or equal to 0.5 µm and less than or equal to 4 µm and a maximum lateral extent d of greater than or equal to 0.5 µm and less than or equal to 50 µm. Security feature for arrangement on a value element, in particular a value document, the security feature comprising a plurality of optically variable elements according to one of Claims 9 until 14 includes. Data carrier, in particular chip card, identification document and/or valuable document, with a security feature Claim 15 .

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