Release coat formulation, method for producing pigments or foil security features

Abstract

The invention relates to a release coat formulation for producing a water-soluble release coat, in particular for the production of pigments or foil security features, comprising at least one binder selected from a polysaccharide, a polyvinyl alcohol, a polyethylene glycol, a polyacrylic acid and a combination thereof; and at least one solvent selected from water, an organic solvent and a combination thereof; wherein the release coat formulation is crosslinking-resistant and is free from crosslinking inhibitors. Furthermore, a method for producing pigments or foil security features is provided.

Description

[0001] Release coat formulation, process for creating pigment or film security features

[0002] The invention relates to a release coat formulation, a use thereof, a method for producing a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite or a release coat-carrier substrate-foil security material composite, a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite, a release coat-carrier substrate-foil security material composite, a method for producing a pigment, a ColourShift pigment, a foil security feature or a LEAD security strip, a pigment and a foil security feature.

[0003] Commercially available color-shifting pigments, also called color-shifting pigments, are typically based on solvent-based stripping processes. In this process, a pigment material is applied to a release layer, which is provided on a carrier film, and then removed by dissolving the release layer. Removing a release layer is also called stripping. The release layer, also called a release coat, is typically based on a solvent-soluble material. Examples of such materials are isobutyl methacrylate polymers or urea resins, which are dissolved during stripping with organic solvents (e.g., ethyl acetate). A color-shifting pigment can also be called a color-shifting thin-film element. A color-shifting thin-film element presents a different color impression to the viewer depending on the viewing angle.

[0004] In the production of typical foil security features, such as a lead security strip, a carrier film, particularly a coated one, is partially covered with a release coat, also known as a wash coating, as described, for example, in EP1310381 A2. The carrier film is first coated with a layer of UV varnish and then partially covered with the wash coating. The coated carrier film is then coated with a foil security material, for example, by vapor deposition of metal. The areas of the foil security material intended to be on the wash coating are washed off along with the wash coating during stripping. The carrier film, with the remaining areas of the foil security material and other layers, forms the foil security feature or a base for the foil security feature.

[0005] A colour-shift pigment or a foil security feature may, for example, contain an absorber material, a dielectric material, and / or a reflector material, as described, for example, in WO2022 / 083887 Al, WO2021 / 115628 Al, WO2019 / 057322 Al, and DE102022002099 Al.

[0006] If the stripping process for the production of pigments or film security features can be carried out with water, the process is more environmentally friendly and, due to the reduced risk of explosion, significantly safer than with organic solvents. An exemplary process for producing platelet-shaped pigments, in which the stripping process is carried out with water, is known from WO2022 / 083887 Al. However, in this process, a crosslinking inhibitor, such as a polymerization inhibitor or an antioxidant, is typically added to the material of the release layer to be removed with water, e.g., PVP (polyvinylpyrrolidone), to prevent undesired crosslinking, such as polymerization and / or bonding, of the release layer, which can be caused, for example, by radiation and / or high temperatures during the application and / or drying of the pigment material.Without a crosslinking inhibitor, when applying such a release coat, residues of the release coat may remain on the carrier film and / or in the pigment after washing or stripping with water. This can impair the quality of the film security feature or the pigment. Furthermore, this can lead to pigment agglomerates when the pigment dries, which complicate its use in a printing process, e.g., intaglio printing or screen printing. In addition, reproducible surface treatment of the pigment is often not possible. Typical crosslinking inhibitors are selected from a phenol derivative, in particular dibutylmethylphenol or...Butylhydroxytoluene (BHT), butylhydroxyanisole (BHA), 4-methoxyphenol (MEHQ), tert-butylmethoxyphenol or a thioether-functionalized phenol derivative, an aromatic amine, alkylated phenyl-alpha-naphthylamine, octylated diphenylamine, butylated diphenylamine, tris-(di-tert-butylphenyl)phosphite, 4-hydroxy-2,2,6,6-tetramethylpiperidinyloxyl (4-hydroxy-TEMPO), a tocopherol, in particular tocopherol acetate, beta-carotene, ubiquinone-10, glutathione, cysteine, thiolactic acid, melatonin, a gallate, in particular ethyl gallate, propyl gallate, octyl gallate or dodecyl gallate, ascorbic acid, ascorbyl palmitate, ascorbyl stearate, citric acid, a carotenoid, a polyphenolic compound, in particular a flavonoid, an anthocyanin or a phytoestrogen, or a mixture of two or more of the aforementioned substances.

[0007] The task is to provide a release coat formulation with a simple composition and good application behavior, especially in the production of pigments or film security features.

[0008] The invention is defined in the independent claims. The dependent claims relate to preferred embodiments.

[0009] One embodiment relates to a release coat formulation for producing a water-soluble release coat, in particular for the production of pigments or foil security features, containing

[0010] at least one binder selected from a polysaccharide, a polyvinyl alcohol, a polyethylene glycol, a polyacrylic acid and any combination thereof; and

[0011] at least one solvent selected from water, an organic solvent and any combination thereof;

[0012] the release coat formulation is crosslinking-resistant and free of crosslinking inhibitors.

[0013] Surprisingly, the release coat formulation enables excellent solubility of the resulting release coat in water, even without the addition of a crosslinking inhibitor. The combination of the binder and solvent in the release coat formulation alone provides a high degree of crosslinking resistance for both the formulation and the resulting release coat. This is particularly true when the release coat formulation is used to produce a release coat in the manufacture of pigments or film security features. The excellent solubility of the release coat produced with the formulation in water is maintained, due to its crosslinking resistance, even after coating, vapor deposition, and / or metallization, especially after exposure to temperature and / or radiation.The release coat formulation can be used to manufacture a security feature or pigment because, after washing or stripping, no residue remains on the carrier film of the security feature or in the pigment itself. This improves the quality of the security feature or pigment produced using the release coat formulation. In particular, the pigment can be produced in good, reproducible quality for intaglio, gravure, or screen printing applications. Using the release coat formulation in pigment production prevents the formation of pigment agglomerates during drying. This facilitates the use of the pigment in a printing process. Furthermore, it enables reproducible surface treatment of the pigment.Furthermore, the release coat formulation exhibits excellent processing properties, particularly when applying the release coat formulation to a carrier film or substrate, e.g., by a printing process.

[0014] The crosslinking resistance of the release coat formulation can include resistance to polymerization and / or clumping of the resulting release coat. Furthermore, the dried release coat can be block-free under dry conditions at room temperature.

[0015] The term "containing" can, in variations of the foregoing embodiment, be understood as "consisting of". The pigments can have any shape, e.g., be platelet-shaped. The binder can be a derivative of the polysaccharide, polyvinyl alcohol, polyethylene glycol, and / or polyacrylic acid. Modified starches can be derivatives of the polysaccharide starch, modified, for example, with phosphate groups and / or carboxyl groups.

[0016] The polysaccharide may be selected from a modified wheat starch, gum arabic, a modified potato starch, carboxymethylcellulose, or any combination thereof. The modified wheat starch may be selected from Crespotec 1408, Crespotec 1409, and / or Crespotec 1414 (all manufactured by Crespel & Deiters), or any combination thereof. The gum arabic may be Worlee gum arabic. The carboxymethylcellulose may be selected from Ambergum 1221 and / or Ambergum 3021 (both manufactured by Ashland), or any combination thereof. The modified potato starch may be selected from Sobotex 5305 NN, Sobotex AM, Sobex 222, or any combination thereof, or any combination thereof. The polyvinyl alcohol may be Poval 5-74 (manufactured by Kuraray).The polyethylene glycol may contain or be PEG4000 (manufacturer Sigma-Aldrich). The polyacrylic acid may contain or be Sokalan PA 20 (manufacturer BTC). The latter is an acrylic acid homopolymer.

[0017] The binder can be present in the release coat formulation in an amount of 2 to 90 wt.%, preferably 5 to 80 wt.%, more preferably 10 to 20 wt.%. These ranges can be understood as the solids content of the release coat formulation. The binder can be a natural, renewable and / or at least partially biodegradable material.

[0018] The solvent can be present in the releasecoat formulation in an amount of 10 to 98 wt.%, preferably 20 to 95 wt.%, more preferably 80 to 90 wt.%.

[0019] The organic solvent may be miscible with water, at least to a limited extent. The organic solvent contained in the release coat formulation may be selected, for example, from an alcohol, a carboxylic acid ester, a ketone, a glycol ether, an ether, or any combination thereof. In particular, a cyclic form of one or more of the aforementioned organic solvents may be selected. The alcohol may be selected from ethanol, 1-propanol, 2-propanol, ethylene glycol, propylene glycol, 1-butanol, 2-butanol, 2-methyl-1-propanol, or any combination thereof.

[0020] If the release coat formulation contains an alcohol or an alcohol mixture as an organic solvent with a content in the range of 3 to 25 wt.%, contamination of the release coat formulation can be avoided by reducing or eliminating the use of biocides and / or an improvement in the flow of the release coat formulation can be achieved when applying it with a pressure process.

[0021] The release coat formulation can be completely water-soluble, in particular at least 98 to 100% water-soluble. The binder content of the release coat formulation and / or the release coat produced therewith can be substantially completely water-soluble, in particular at least 98 to 100% water-soluble. The release coat formulation can have a viscosity in the range of 30 to 400 mPas, preferably 50 to 250 mPas, at a shear rate in the range of 2 to 2500 1 / s and a binder content of less than 40 wt.%, preferably less than 30 wt.%, more preferably less than 20 wt.%. The aforementioned shear rate can be achieved, for example, during the filling and / or emptying of the cells of a gravure printing cylinder when applying the release coat to the substrate in a gravure printing process.

[0022] The release coat formulation can be shear-thinning at shear rates above 1000 1 / s, preferably above 500 1 / s. The term "shear-thinning" can be understood to mean that the viscosity decreases with increasing shear rate. The viscosity of the release coat formulation can decrease by more than 10%, preferably 10% to 50%, and more preferably 10% to 30% with increasing shear rates from 1000 to 2500 1 / s, preferably 500 to 2500 1 / s. The aforementioned properties of the release coat formulation result in particularly favorable processing behavior, especially when applying the formulation to a carrier film or substrate, e.g., by a printing process. The viscosity of the release coat formulation can decrease with increasing shear rates from 2 to 2500 1 / s, particularly continuously.

[0023] The release coat formulation can become increasingly shear-thinning with increasing shear rates, the higher the binder content. Conversely, the viscosity of the release coat formulation can decrease more significantly with increasing shear rates, the higher the binder content.

[0024] The viscosity of the release coat formulation can decrease by less than 30%, preferably by 10% to 30%, with increasing shear rates from 2 to 1000 1 / s, preferably from 2 to 500 1 / s. The viscosity of the release coat formulation can decrease by 10% to 50%, preferably by 10% to 40%, with increasing shear rates from 2 to 2500 1 / s.

[0025] Another embodiment relates to the use of a release coat formulation according to the preceding embodiment or variations thereof for the manufacture of a pigment, a color shift pigment, a security feature, an EEAD security strip, a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite, or a release coat-carrier substrate-security feature composite. In all embodiments and variations thereof, the pigment material and / or the security feature may comprise at least one material selected from an absorber material, a dielectric material, a reflector material, a magnetic reflector material, and any combination thereof. The magnetic reflector material may be configured as a magnetic reflector assembly.The release coat-support substrate-pigment material composite and / or the release coat-support substrate-foil safety material composite can have the absorber material, the dielectric material, the reflector material, and / or the magnetic reflector material as one or more layers.

[0026] In all embodiments, the absorber material can be selected from aluminum, chromium, copper, iron, nickel, cobalt, silver, gold, or alloys of the aforementioned metals, particularly in thin and / or semi-transparent layers, e.g., with a thickness of 2–10 nm. The dielectric material can be selected from SiCh, MgF₂, T₂O₂, and / or ZnS. The reflector material can be selected from aluminum, chromium, copper, iron, nickel, cobalt, silver, gold, or alloys of the aforementioned metals, particularly in thick and / or reflective layers, e.g., with a thickness of 30–70 nm. The magnetic reflector material can be selected from FeSi, particularly alloys of iron and silicon, iron, cobalt, nickel, and alloys of iron, cobalt, and / or nickel. The magnetic reflector material can be selected from aluminum-containing (Al) alloys, particularly with the compositions FexAly, CoxAly, and NixAly.The magnetic reflector material can be selected from chromium-containing (Cr) alloys and oxides, in particular with the compositions FexCry, AlxFeyCrz, CrO2, CoxAlyCrz and NixAlyCrz. A magnetic reflector assembly can include at least one of the magnetic reflector materials in a layered structure, e.g. a sandwich layered structure with, for example, aluminum interlayers.

[0027] One embodiment relates to a method for producing a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite, or a release coat-carrier substrate-film safety material composite, comprising at least partial application of a layer of a release coat formulation according to the preceding embodiment or a modification thereof onto a carrier substrate, in particular a coated carrier substrate, and formation of a water-soluble release coat. The formation of the water-soluble release coat may include drying it. The method may include a step for providing the carrier substrate. The carrier substrate may be a carrier film, e.g., a continuous film. The carrier substrate material may contain at least one element selected from polyethylene terephthalate (PET), polyethylene (PE), polymethyl methacrylate (PMMA), and polycarbonate (PC), and any combination thereof.The process for producing a release coat-support substrate composite can also be called a process for producing a water-soluble release coat.

[0028] At least one layer, and in particular at least five layers, of one or more pigment materials or one or more foil safety materials can be applied to the release coat. An absorber material, a dielectric material, a reflector material, a dielectric material, and an absorber material can each be applied to the release coat as at least one layer, in that order. Alternatively, an absorber material, a dielectric material, materials of a magnetic reflector assembly, a dielectric material, and an absorber material can each be applied to the release coat as at least one layer, in that order. The at least one layer can be applied to the entire surface of the substrate or to the already coated substrate.The substrate can be at least partially coated with at least one UV varnish and / or at least one thermoplastic before the release coat formulation is applied. The UV varnish can be selected, for example, from Lumogen OVD Varnish 311® (BASF) and / or Lumogen OVD Varnish 312® (BASF). Other materials can be included, and / or additional or alternative layers of other materials can be applied, such as other thermoplastics like PET or PMMA. These layers can be applied to the release coat with a thickness of 1–5 µm.

[0029] In further embodiments, a release coat-support substrate composite, a release coat-support substrate-pigment material composite, a release coat-support substrate-foil safety material composite, or a water-soluble release coat is provided, obtained, or made available by a method according to the preceding embodiment or a modification thereof. The release coat-support substrate composite, the release coat-support substrate-pigment material composite, or the release coat-support substrate-foil safety material composite can have at least seven layers arranged one above the other in the following order: support substrate, release coat, absorber, dielectric, reflector, dielectric, and absorber; or in the following order: support substrate, release coat, absorber, dielectric, magnetic reflector assembly, dielectric, and absorber. In a composite with a pigment material, the release coat can be provided over the entire surface of the support substrate.In combination with a foil safety material, the release coat can be applied to the substrate in certain areas.

[0030] One embodiment specifies a method for producing a pigment, a ColourShift pigment, a foil security feature or a LEAD security strip, comprising the steps

[0031] - at least partially applying a layer of a release coat formulation according to the preceding embodiment or a modification thereof to a carrier substrate, in particular to a coated carrier substrate, and forming a water-soluble release coat; - covering the carrier substrate at least partially provided with the release coat with a pigment material or foil security material; and

[0032] - Washing off the release coat with water from the carrier substrate.

[0033] The formation of the water-soluble release coat may involve drying it.

[0034] In the step of covering the carrier substrate, which is at least partially coated with the release coat, with a pigment material or a security film material, at least one layer, and in particular at least five layers, of one or more pigment materials or one or more security film materials can be applied. An absorber material, a dielectric material, a reflector material, a dielectric material, and an absorber material can each be applied to the release coat as at least one layer, in that order. Alternatively, an absorber material, a dielectric material, materials of a magnetic reflector assembly, a dielectric material, and an absorber material can each be applied to the release coat as at least one layer, in that order. The at least one layer can be applied to the entire surface of the carrier substrate or to the already coated carrier substrate.The substrate can be at least partially coated with at least one UV varnish and / or at least one thermoplastic before the release coat formulation is applied. The UV varnish can be, for example, Lumogen OVD Varnish 311® (BASF) and / or Lumogen OVD Varnish 312® (BASF). Other materials can be included, and / or additional or alternative layers of other materials can be applied, such as other thermoplastics like PET or PMMA. These layers can be applied to the release coat with a thickness of 1–5 µm.

[0035] In the foregoing embodiment, a release coat-support substrate composite, particularly according to one of the foregoing embodiments or variations thereof, can be formed by the step of applying the layer of the release coat formulation and forming the water-soluble release coat. Furthermore, a release coat-support substrate composite, a release coat-support substrate-pigment material composite, or a release coat-support substrate-security material composite, particularly according to one of the foregoing embodiments or variations thereof, can be formed by the step of applying the layer of the release coat formulation and forming the water-soluble release coat and / or by the step of covering the support substrate provided with the release coat with a pigment material or security film material.

[0036] In all embodiments of the manufacturing process, the application of the release coat formulation layer can be achieved by a printing process, e.g., gravure printing, flexographic printing, or doctor blade application. Formation of the release coat may involve drying the release coat formulation layer. Removing the release coat can also be called washing or stripping.

[0037] The carrier substrate can be uncoated or coated, particularly before the application of the release coat formulation. For the production of a pigment or a ColourShift pigment, the carrier substrate can be uncoated, e.g., an uncoated carrier film. For the production of a foil security feature or a LEAD security stripe, the carrier substrate can be coated with at least one layer, e.g., a carrier substrate coated with at least one UV lacquer and / or at least one thermoplastic, in particular a carrier film. For the production of a pigment, a ColourShift pigment, a foil security feature, or a LEAD security stripe, the pigment material can comprise at least one material selected from Cr, Al, SiCh, and any combination thereof.To create a foil security feature or a lead security strip, the foil security material may contain at least one material that is part of a foil security feature, e.g., a metal and / or magnetic ink. The pigment material and / or the foil security material may each contain at least one layer of one or more of the aforementioned materials.

[0038] The pigment production process may include at least one of the following additional steps: dewatering the pigment, grinding the pigment, re-dewatering the pigment, and drying the pigment. The pigment may exist as a plurality of pigment particles. The pigment may be suspended in water after washing and before drying.

[0039] The process for manufacturing a foil security feature can include the following steps: covering the substrate, particularly the coated substrate, in predetermined areas with the release coat formulation; and covering, e.g., by vapor deposition, the release coat-free areas and the release coat-covered areas of the substrate with the foil security material. The foil security material can contain a metal, e.g., a Cr / Al or Cr / SiCh / Al layer system. The foil security material applied to the release coat can be washed off along with the release coat, also known as wash paint. In the manufacturing of a foil security feature, the substrate, together with the areas of the foil security material remaining after washing, can form an intermediate product or the final product of the foil security feature.

[0040] Another embodiment relates to a pigment, in particular a ColourShift pigment, obtained or obtainable by a process comprising the steps of the process according to the preceding embodiment or variations thereof. A further embodiment relates to the use of a pigment according to the preceding embodiment or variations thereof in a printing ink. One embodiment relates to a foil security feature, in particular a LEAD security strip, obtained or obtainable by a process comprising the steps of the process according to the preceding embodiment or variations thereof.

[0041] The advantages mentioned with reference to the releasecoat formulation or variations thereof apply accordingly to the use of the same, to the method for producing a releasecoat-carrier substrate composite, to the releasecoat-carrier substrate composite, to the method for producing a pigment, a ColourShift pigment, a foil security feature or a LEAD security stripe, to the pigment and to the foil security feature.

[0042] Further features of the invention can be found in the claims, the figures and the figure description.

[0043] The invention is explained in more detail below with reference to exemplary embodiments and the accompanying schematic drawings, which also disclose essential features of the invention. These exemplary embodiments serve only for illustration and are not to be interpreted as limiting. For example, a description of an exemplary embodiment with a plurality of elements or components is not to 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 exemplary embodiments may be combined with one another unless otherwise specified. Modifications and variations described for one of the exemplary embodiments may also be applicable to other exemplary embodiments.To avoid repetition, identical or corresponding elements in different figures are designated with the same reference symbols and are not explained multiple times. The figures show:

[0044] Fig. 1 shows an IR analysis of a comparative example V;

[0045] Fig. 2 shows an IR analysis of example 6;

[0046] Fig. 3a schematically shows a method for producing a release coat-carrier substrate composite; Fig. 3b schematically shows a method for producing a pigment, a ColourShift pigment, a foil security feature, or a LEAD security strip; Fig. 4a shows a scanning electron micrograph of the comparative example;

[0047] Fig. 4b Results of a gel permeation chromatography investigation for the comparative example V;

[0048] Fig. 5 is a diagram showing the results of rheological investigations of release coat formulations of examples 1 to 9 and of comparison example V; and Fig. 6 is a diagram showing the results of rheological investigations of the release coat formulations of examples 1 to 9 and of comparison example V.

[0049] When describing value ranges, specifying a broad range with narrower alternative or preferred ranges also reveals ranges that can be formed by any combination of specified lower range limits with specified upper range limits.

[0050] Examples

[0051] Release coat formulations were prepared containing the following exemplary binders: polyvinyl alcohol, polyethylene glycol, polysaccharide, or polyacrylic acid. In one example, Poval 5-74 was used as the polyvinyl alcohol. PEG4000 was used as an example of polyethylene glycol. Polysaccharides used included a modified wheat starch, gum arabic, a modified potato starch, or carboxymethylcellulose. Cre-spotec 1408 was used as an example of a modified wheat starch. In one example, gum arabic from Worlee was used. Three different modified potato starches were used: Sobotex 5305 NN, Sobotex AM, and Sobex 222. Ambergum 1221 was used as an example of a carboxymethylcellulose. Sokalan PA 20 was used as an example of a polyacrylic acid.Furthermore, as a comparative example V, a release coat formulation containing polyvinylpyrrolidone (PVP) as a binder, namely Sokalan K30P, was produced. The formulations of the examples and comparative example V were each produced with a high and a low binder content, as can be seen in Table 1.

[0052] The release coat formulations in the examples and the comparison example V did not contain any crosslinking inhibitor. As explained above, crosslinking inhibitors prevent polymerization, crosslinking, and / or caking within the release coat in the prior art. Table 1 shows the specifications of the respective release coat formulations with the binders used. The viscosity of the release coat formulations was measured at various shear rates, as shown in Table 1, using a Modular Compact Rheometer MCR 302, manufactured by Anton Paar, measuring system CP50-1, at 23°C.

[0053] In the examples and in comparative example V, release coats were produced using the respective release coat formulations. In each case, a layer of the respective release coat formulation was applied to a carrier substrate in a single step, forming a water-soluble release coat, as schematically illustrated in Fig. 3a. A 15 µm thick PET film carrier substrate (RPK film, Mitsubishi Polyester Film GmbH) was used in each case. A release coat layer with a wet thickness of 40 µm and a dry basis weight of 2 g / m² was then applied to this substrate. 2 The black, k Control Coater coating (Erichsen) was applied and dried using a spiral doctor blade. The dry basis weight can range from 2 to 20 g / m². 2The release coat layer was applied at room temperature. It was then dried at 80 °C on a hot plate for one minute. In this way, each release coat-substrate composite was created.

[0054] The release coats applied to the film substrate were then exposed to electromagnetic radiation similar to that emitted during vapor deposition with the pigment material SiCh (silicon dioxide), without actually coating the release coats with the material. This was achieved using electron beam evaporation in a Pfeiffer BoxCoater Classic 580 at a chamber pressure of approximately 5 x 10 5mbar, a voltage of 5 keV, and a current of 100 mA. The amount of SiCh deposited onto a dummy film had a layer thickness of 40 pm. The release coat layers exposed to the radiation were located at a comparable distance from the radiation source as the dummy film, but not within the deposition area. The advantage of SiCh was that the IR spectrum would have revealed if S1O2 had indeed been deposited onto the release coat, and if so, how much. In alternative examples, Cr (chromium) and / or Al (aluminum) can be used as the pigment material, allowing for optical inspection to determine whether Cr and / or Al were deposited or whether the release layer was merely exposed to radiation. In each example and in the comparison example, the release coat of the substrate covered with the irradiated release coat was removed using TESA4964 double-sided adhesive tape from [Company Name].The TESA adhesive tape, which itself does not exhibit characteristic IR bands that overlapped with the characteristic IR bands of the binders, was removed, and the solubility of the respective release coat in water was verified by IR analysis, as described below. For this purpose, the double-sided adhesive tape was applied with its first adhesive side to a glass microscope slide and with its second adhesive side to the release-coated side of the generated film. The applied release-coated film was cut to the size of the microscope slide and further perforated with a needle to allow water penetration. After perforation, the microscope slide with the applied film was placed in deionized water at a temperature of approximately 50 °C for 15 minutes. The film was then removed from the adhesive tape. The adhesive tape remaining on the microscope slide was then washed again with water for 60 minutes at approximately 50 °C.

[0055] IR analysis was performed using a Smart iTX Thermo Fisher Scientific iS 10 IR spectrometer. The measurement was carried out using the ATR (attenuated total reflection) method with a diamond crystal. For this purpose, the washed adhesive tape, affixed to the microscope slide, was dried in a convection oven at 60 °C for 60 minutes, then placed on the ATR crystal, and the IR spectrum was then measured in the range of 400 to 4000 cm⁻¹. 1 measured.

[0056] Table 1 lists the observed washability, i.e., the solubility of the release coat in water, for each example and for the comparison example V. Only comparison example V showed incomplete solubility of the release coat in water. This was evident after washing the corresponding adhesive tape, which was then tested using IR analysis by detecting the presence of the carbonyl band at approximately 1660 cm⁻¹. 1, which is characteristic of PVP. Fig. 1 shows, as an example for comparison example V, the results of the IR analysis of the water-washed adhesive tape (three measurement curves) and demonstrates the poor washability of PVP. In contrast, the release coats of examples 1 to 9 were completely removed with water, as can be seen in the respective IR analysis after washing the adhesive tape by the absence of IR bands characteristic of the respective release coat material. Fig. 2 shows exemplary IR spectra for example 6 with the binder gum arabic. In IR spectrum 10, a broad band at approximately 1050 cm⁻¹ is visible before washing the adhesive tape with water. 1, which is characteristic of the gum arabic used. After washing, this IR band disappeared in the IR analysis (two measurement curves), i.e., in IR spectra 12 and 14. The IR spectra of examples 1 to 9 each corresponded to the spectrum of the double-sided adhesive tape after washing.

[0057] The solubility behavior of the release coats described in the examples and the comparative example was also observed for the release coats covered with a pigment or dye layer during the production of dye platelets, e.g., a ColourShift ThinFilm pigment, also called ColourShift pigment and / or CS pigment, and during the production of a foil security feature.

[0058] The production of the CS pigment and the security feature each comprised the following steps, as schematically illustrated in Fig. 3b: In step S1, a layer of the respective release coat formulation was applied, at least partially, and in particular at least in certain areas, to the aforementioned PET carrier substrate, forming a release coat. Step S1 included drying the applied release coat at 80 °C. For the production of the ColourShift pigment, the uncoated PET carrier substrate was used. For the production of the security feature, the PET carrier substrate coated with a UV varnish was used. In step S1, a release coat-carrier substrate composite was formed in each case. In step S2, the carrier substrate, at least partially coated with the release coat, was covered with the CS pigment material or the security feature material using PVD.In this process, three layers of materials, either the pigment or the security feature, were applied to the release coat. In step S2, this resulted in a release coat-carrier substrate-pigment material composite or a release coat-carrier substrate-security feature composite. In step S3, the release coat was washed off the carrier substrate with water.

[0059] In CS pigment production, the entire support substrate was covered with the release coat formulation, and the process included the following additional steps: dewatering the pigment, milling the pigment, optional second dewatering, and drying. In step S2, the pigment material was deposited onto the release coat using PVD, creating a Cr / SiCh / Al layer system. Chromium (Cr) was applied as an absorber layer, silicon dioxide (SiCh) as a dielectric layer, and aluminum (Al) as a reflector layer. In the present examples, the Cr layers were produced with a thickness of 4 nm and can be applied with thicknesses ranging from 4 to 10 nm. The SiCh layers were produced with a thickness of 300 nm in the present example and can be applied with thicknesses ranging from 200 to 1000 nm.In this example, the Al layers were produced with a thickness of 40 nm and can be applied with thicknesses ranging from 30 to 60 nm. The resulting CS pigments can have total thicknesses of 0.4 to 3 pm. The CS pigment was produced as described in WO2022 / 083887 Al.

[0060] In the production of the foil security feature, the UV-coated substrate was covered with the release coat formulation in predetermined areas. The PET substrate was printed with the UV varnish Lumogen OVD Varnish 311® (BASF) using gravure printing, as described in EP1310381 A2. The release coat-free areas of the printed substrate and the release coat provided in the predetermined areas of the aforementioned PET substrate were vapor-deposited with at least one metal, in the present examples with a Cr / SiCh / Al layer system, with Cr layer thicknesses of 4 to 10 nm, SiCh layer thicknesses of 200 to 1000 nm, and Al layer thicknesses of 30 to 70 nm. Chromium (Cr) was applied as an absorber layer, silicon dioxide (SiCh) as a dielectric layer, and aluminum (Al) as a reflector layer. The metallized areas on the release coat, i.e. the wash color, were washed off along with the wash color.Unlike the pigment, the film with the remaining metallized areas is the product of the manufacturing process; the washed-off release coat is waste. The production of the security feature was carried out as described by way of example in EP1310381 A2.

[0061] The key advantage of the release coat formulations in Examples 1 to 9 arises from the effect described above: the release coats produced do not crosslink during the respective vapor deposition processes with pigment material or the material of the security feature (i.e., PVD of Al, Cr, or SiCh) and therefore remain water-soluble. This results in a reduced amount of wash water required during the stripping process to remove the coated release coat, even at high machine speeds of up to 120 m / min. In contrast, when using PVP as the release coat, crosslinking of the release coat during the application of the pigment material or the security feature material often prevents it from being washed off, even with very large quantities of water.

[0062] In the final step of CS pigment production, the pigment is dried in a vacuum dryer. Undesirable agglomerations of the pigment and residues of the respective release coat were not detectable after drying when using the formulations of Examples 1 to 9. However, when using the release coat formulation of Comparative Example V, agglomerations and residues of the PVP release coat were observed, as explained below, rendering such pigments unsuitable for printing applications.

[0063] The particle size distribution of the CS pigment after the drying process was checked using a laser diffraction analyzer (Mastersizer 3000 from Malvern Panalytical) with an Aero S dry dispersion unit. Agglomerates with sizes ranging from 100 to 2000 pm were detected in the samples of comparison example V. No agglomerates were formed when the CS pigment was produced using the formulations of examples 1 to 9. In these cases, the particle size distribution previously established by milling, with a D90 of 1 to 100 pm, was maintained even after the drying process.

[0064] Additionally, the presence of release coat residues in the CS pigment and the resulting agglomeration / clumping of the CS pigment in the release coat formulation of comparison example V were demonstrated using scanning electron microscopy (SEM) images. These images were acquired using the JSM-6390 (SEM + EDX) MP141100065 instrument from JEOL GmbH Germany in secondary electron imaging mode and with an accelerating voltage of 10 kV. An exemplary SEM image for comparison example V is shown in Fig. 4a. The agglomerations of the CS pigment and the release coat residues are clearly visible. These results were confirmed for comparison example V using gel permeation chromatography (GPC). Fig. 4b shows exemplary results of the GPC using a fresh PVP release coat formulation with 2 wt% PVP in water and its measurement curve 20 of Fig.4b, as well as based on a water sample of the wash water containing approximately 0.5 wt.% PVP after milling the CS pigment produced with a 35 wt.% PVP release coat formulation and its measurement curve 22 of Fig. 4b. The x-axis represents the molar mass in the form of a polyethylene oxide equivalent molar mass. The y-axis represents the percentage distribution over the molar mass. These investigations showed a significant increase in the mean molar mass of the PVP and thus a cross-linking of the PVP through the CS pigment production processes.

[0065] In the comparative example, the cause of the pigment particle agglomeration was identified as residues of the PVP release coat. During the drying process, the PVP is heated to its glass transition state. If PVP remains on the pigment particles, it can melt and cause them to clump together. Furthermore, because the pigment surfaces are coated with PVP, a reproducible surface treatment of the pigment is not possible.

[0066] Figures 5 and 6 show rheological investigations of the release coat formulations of Examples 1 to 9 and the comparative example V, where the measurement curves of Examples 1 to 9 are labeled 1 to 9 and the comparative example V. Both figures represent the viscosity as a function of the shear rate. Figure 5 shows the rheological properties of the examples listed in Table 1 and the comparative example with a low binder content, as specified in Table 1, and with relatively low viscosities. Figure 6 shows the rheological properties of the examples listed in Table 1 and the comparative example with a high binder content, as specified in Table 1, and with relatively high viscosities.Among the non-crosslinking formulations of Examples 1 to 9, those release coat formulations that exhibit shear-thinning behavior at high shear rates above 1000 s⁻¹ or above 500 s⁻¹ are characterized by particularly good processability, especially printability. This applies especially to release coat formulations whose viscosity decreases by more than 10.0% with increasing shear rates in the range of 1000 s⁻¹ to 2500 s⁻¹ or 500 s⁻¹ to 2500 s⁻¹.

[0067] The following advantages arise for the production of security features and pigments when using the releasecoat formulation of these embodiments: The resulting releasecoat remains essentially completely water-soluble even after coating processes, particularly vapor deposition processes, in which pigment material or security material is applied to the releasecoat. Very good printing properties are achieved with a very thin releasecoat layer, e.g., with a layer thickness of 200–400 nm. This results in fewer disturbances, e.g., interference between the SiCh control and the reflection signal of the SiCh layer, during vapor deposition with a security material or pigment material, and higher color consistency of the layer thus produced. An increase in the speed of the stripping process, e.g., to 120 m / min, becomes possible while still ensuring complete washing off of the releasecoat.A reduction in the amount of water used in the stripping process of, for example, approximately 5 m³. 3 / h to approx.

[0068] 1.5 m 3 Furthermore, the release coat formulation of various embodiments utilizes a natural, renewable, and biodegradable raw material as a binder. This biodegradability allows for the trouble-free reprocessing of stripping water in conventional wastewater treatment plants. During pigment production, no agglomeration of the pigments occurs during the drying process. This enables reproducible and complete surface treatment of the pigments. The pigments can be used in various printing processes (e.g., intaglio, screen printing, gravure).

[0069] The following advantages are observed with this release coat formulation: The dried release coat produced with this formulation is non-blocking under dry conditions at room temperature. This allows for longer storage of the dried release coat. If the release coat formulation contains an alcohol or an alcohol mixture as an organic solvent with a concentration between 3 and 25% by weight, microbial contamination of the release coat formulation can be prevented, the use of biocides can be reduced or avoided, and the flow of the release coat formulation can be improved when applied using a pressure method. Table 1

[0070] Solvent content

[0071] Viscosity of the release coat formulation

[0072] sungsBinBindemittel demit Waschbarmittel der

[0073] Information about the Re- e Release- spi (Water leasecoats el

[0074] coat- [Weight

[0075] No. and / [mPas] with water Formu- %]

[0076] or after loading steaming shear shear shear shear shear rate rate rate rate rate rate

[0077] 1000 2500

[0078] 21 / s 5001 / s 7501 / s

[0079] 1 / s 1 / s

[0080] Poval 5- 12.0% 97.0 89.7 89.0 87.4 83.1

[0081] 74

[0082] 1 Water completely (Company

[0083] Kuraray) 16.0% 489.5 461.7 452.8 435.0 369.1

[0084] PEG4000 Water - 40.0% 51.8 47.8 47.7 47.5 47.5

[0085] (Sig Ethanol- 2 completely ma- mixture)

[0086] Aldrich) (1:1) 50.0% 94.1 91.6 91.4 91.1 90.7 Crespotec

[0087] 1408 10.0% 979.4 59.2 50.3 46.2 34.9

[0088] (Cre-3 Water completely spel &

[0089] Deiters 15.0% 2073.4 169.6 148.5 135.4 101.4

[0090] GmbH)

[0091] Sobex 222 Water - 11.7% 74.0 63.9 61.7 60.0 53.3

[0092] (Company SüdEthanol- 4 complete strength mixture)

[0093] GmbH) (8:1) 15.9% 234.4 193.2 175.3 167.9 142.0

[0094] Amber- 8.0% 97.1 78.1 77.1 76.1 71.1

[0095] gum 1221

[0096] 5 Water complete (Ashland company) 15.0% 1360.9 868.9 802.1 750.9 573.2

[0097] Gum Water- 6 20.8% 36.7 36.3 36.3 36.3 36.2 completely Arabic Ethanol-

[0098]

[0099] (Wor- Mixture company)

[0100] lee) (5:1) 29.4% 146.0 111.8 112.1 112.2 110.7

[0101] Delivery form (45

[0102] 100.0% 544.5 519.9 515.0 513.6 500.0

[0103] Sokalan % Fest7 PA 20 body) complete (BTC company)

[0104] 20%

[0105] 80% 85.1 84.0 84.0 84.0 84.0

[0106] Water

[0107] Sobotex

[0108] 20.0% 56.2 45.7 44.6 43.7 40.6

[0109] AM

[0110] 8 (Company SüdWasser full strength)

[0111] 40.0% 2072.4 787.7 722.9 679.2 506.5

[0112] GmbH)

[0113] Sobotex

[0114] 31.0% 92.6 33.5 30.5 28.6 23.4

[0115] 5305 NN

[0116] 9 (Company SüdWasser full strength)

[0117] 36.0% 2122.5 899.2 774.7 690.2 472.2

[0118] GmbH)

[0119] VerSokalan K

[0120] 25.0% 61.3 62.7 62.0 61.5 61.4

[0121] equal- 30 P incomplete- ethanol

[0122] Example (PVP; Company: dig V BASF) 35.0% 243.8 248.9 248.0 247.3 239.7

[0123]

Claims

Patent claims 1. Release coat formulation for producing a water-soluble release coat, in particular for the manufacture of pigments or film security features, comprising at least one binder selected from a polysaccharide, a polyvinyl alcohol, a polyethylene glycol, a polyacrylic acid and any combination thereof; and at least one solvent selected from water, an organic solvent and any combination thereof; the release coat formulation is crosslinking-resistant and free of crosslinking inhibitors.

2. Releasecoat formulation according to claim 1, wherein the polysaccharide is selected from a modified wheat starch, a gum arabic, a modified potato starch, a carboxymethylcellulose and any combination thereof.

3. Releasecoat formulation according to any one of the preceding claims, wherein the modified potato starch is selected from Sobotex 5305 NN, Sobotex AM, Sobex 222 and any combination thereof.

4. Releasecoat formulation according to any one of the preceding claims, wherein the binder is present in an amount of 2 to 90 wt.%, preferably 5 to 80 wt.%, more preferably 10 to 20 wt.%; and / or where the binder is a natural, renewable and / or biodegradable material.

5. Releasecoat formulation according to any one of the preceding claims, wherein the solvent is present in an amount of 10 to 98 wt.%, preferably 20 to 95 wt.%, more preferably 80 to 90 wt.%.

6. Releasecoat formulation according to any one of the preceding claims, wherein the organic solvent is selected from an alcohol, a carboxylic acid ester, a ketone, a glycol ether, an ether and any combination thereof, in particular a cyclic form of one or more of the aforementioned organic solvents; and / or wherein the alcohol is selected from ethanol, 1-propanol, 2-propanol, ethylene glycol, propylene glycol, 1-butanol, 2-butanol, 2-methyl-l-propanol and any combination thereof.

7. Releasecoat formulation according to any one of the preceding claims, wherein the release coat formulation is completely water-soluble; and / or wherein the binder component of the release coat formulation and / or the release coat produced thereby is completely water-soluble, in particular at least 98 to 100% water-soluble; and / or wherein the release coat formulation, at a shear rate in the range of 2 to 25001 / s and a binder content of less than 40 wt.%, preferably less than 30 wt.%, more preferably less than 20 wt.%, has a viscosity in the range of 30 to 400 mPas, preferably 50 to 250 mPas.

8. Releasecoat formulation according to any one of the preceding claims, where the release coat formulation is shear-thinning at shear rates above 10001 / s; and / or wherein the viscosity of the release coat formulation decreases by more than 10%, preferably 10% to 50%, more preferably 10% to 30% with increasing shear rates from 1000 to 25001 / s; and / or wherein the viscosity of the release coat formulation decreases with increasing shear rates from 2 to 25,000 l / s, preferably from 10,000 l / s, particularly continuously; and / or wherein the release coat formulation is shear-thinning with increasing shear rates the higher the binder content; and / or the viscosity of the release coat formulation decreases more sharply with increasing shear rates the higher the binder content; and / or wherein the viscosity of the release coat formulation decreases by less than 30%, preferably by 10% to 30%, with increasing shear rates from 2 to 10001 / s; and / or wherein the viscosity of the release coat formulation decreases by 10 to 50%, preferably by 10 to 40%, with increasing shear rates from 2 to 25001 / s.

9. Use of a release coat formulation according to any of the preceding claims for the manufacture of a pigment, a ColourShift pigment, a foil security feature, a LEAD security strip, a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite or a release coat-carrier substrate-foil security material composite.

10. Method for producing a release coat-carrier substrate composite, a release coat-carrier substrate-pigment material composite or a release coat-carrier substrate-film safety material composite, with - at least partially applying a layer of a release coat formulation according to one of claims 1 to 8 to a support substrate, in particular to a coated support substrate, and forming a water-soluble release coat (SO).

11. Method according to claim 10, wherein at least one layer, in particular at least five layers, of one or more pigment materials or one or more film safety materials are applied to the release coat; and / or wherein an absorber material, a dielectric material, a reflector material, a dielectric material and an absorber material are applied to the release coat in that order, each as at least one layer; and / or wherein an absorber material, a dielectric material, materials of a magnetic reflector assembly, a dielectric material and an absorber material are applied to the release coat in that order, each as at least one layer; and / or wherein the carrier substrate is or is coated with at least one UV varnish and / or at least one thermoplastic before the application of the releasecoat formulation.

12. Releasecoat-support substrate composite, releasecoat-support substrate-pigment material composite or releasecoat-support substrate-film safety material composite, obtained using a method according to claim 10 or 11.

13. Release coat-support substrate composite, release coat-support substrate-pigment material composite or release coat-support substrate-film safety material composite according to claim 12, comprising at least seven layers arranged one above the other in a sequence according to substrate, release coat, absorber, dielectric, reflector, dielectric and absorber or in a sequence according to substrate, release coat, absorber, dielectric, magnetic reflector assembly, dielectric and absorber.

14. Method for producing a pigment, a ColourShift pigment, a foil security feature or a LEAD security strip, comprising the steps - at least partially applying a layer of a release coat formulation according to one of claims 1 to 8 to a carrier substrate, in particular to a coated carrier substrate, and forming a water-soluble release coat (Sl); - Covering the carrier substrate, which is at least partially coated with the release coat, with a pigment material or foil safety material (S2); and - Washing off the release coat with water from the carrier substrate (S3).

15. Method according to claim 14, wherein, by the step of applying the layer of the releasecoat formulation and forming the water-soluble releasecoat (S1) and / or by the step of covering the carrier substrate provided with the releasecoat with a pigment material or foil security material (S2), a releasecoat-carrier substrate composite, a releasecoat-carrier substrate-pigment material composite or a releasecoat-carrier substrate-foil security material composite, in particular according to claim 12 or 13, is formed.

16. Pigment, in particular ColourShift pigment, or foil security feature, in particular LEAD security strip, obtained by a method comprising the steps of the method according to claim 14 or 15.

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