Security ink compositions and machine-readable security features derived therefrom

Abstract

A security ink composition comprising at least one non-luminescent undoped Y3Fe5-xMxO12 based pigment wherein x satisfies the condition 0 < = x < = 1.25; m is selected from the group consisting of aluminum, gallium or calcium and mixtures thereof; and wherein upon drying and / or curing, at least one machine-readable security feature derived from the application of the security ink composition, preferably printing, has a comprehensive susceptibility of at least about 200 x 10-12 m3, and exhibits ferromagnetic resonance (FMR) characteristics for authentication purposes. A method for authenticating a machine-readable security feature derived from a security ink composition.

Description

Technical Field

[0001] The present invention relates to the field of ferromagnetic security inks suitable for printing detectable machine-readable security features on substrates, in particular on security documents and / or articles. Background Art

[0002] With the continued improvement in the quality of color copies and prints and attempts to protect security documents from counterfeiting, tampering or illegal copying, it has been conventional practice to introduce various security features into these documents, such as banknotes, value documents or cards, transportation tickets or cards, tax banderols and merchandise labels that do not have a reproducible effect.

[0003] Security features used, for example, in security documents can be categorized as "covert" and "explicit" security features. The protection provided by covert security features relies on the concept that such features are hidden, typically requiring specialized equipment and knowledge for their detection, whereas "explicit" security features are easily detectable with unaided human senses, e.g., such features may be visible and / or detectable via tactile senses, while still being difficult to produce and / or replicate.

[0004] Machine readable security inks, such as magnetic inks, luminescent inks and IR absorbing inks, have been widely used in the field of security documents, in particular for banknote printing, to give security documents additional hidden security features. The protection of security documents from counterfeiting and illegal copying provided by hidden security features relies on the concept that such features usually require specialized equipment and knowledge for their detection. In the field of security and protection of valuable documents and valuable goods or articles from counterfeiting, tampering and illegal copying, it is known in the art to apply machine readable security inks by different printing methods, including printing methods using high viscosity or paste inks, such as offset printing, letterpress printing and gravure printing (also known in the art as engraved steel molds or copperplate printing), printing methods using liquid inks, such as rotogravure printing, flexographic printing, screen printing and inkjet printing.

[0005] Magnetic detection methods are known in the art and provide covert detection of security documents and items. Paramagnetic detection methods have been described in WO 2020 / 245280 A1, US 4376264 or US2010 / 224819 A1. Another magnetic detection method relies on ESR / NMR detection technology, for example US 5986550. Magnetic resonance detection can be used for ferrimagnetic, ferromagnetic or paramagnetic security features.

[0006] Yet another magnetic detection method relies on ferromagnetism. Ferromagnetism is a mechanism by which certain materials form permanent magnets or are attracted to magnets. It is known in the art that ferromagnetism is the strongest kind of magnetism, and ferromagnetism detection methods provide a strong magnetic signal that can be used, for example, in ATMs or high-speed sorting (HSS) machines for fast and reliable magnetic detection.

[0007] In contrast, paramagnetic substances generally provide low intensity signals and require higher B fields and excitation frequencies for higher concentrations. Therefore, paramagnetic substances need to be included in security ink compositions at fairly high concentrations. This can lead to non-uniformity issues and add additional costs. NMR detection requires complex instrumentation and methods, which makes them impractical to incorporate into ATM and HSS machines. Therefore, ferromagnetic detection methods and security features based thereon provide practical and effective detection and authentication services for security documents and / or articles.

[0008] Additionally, modern machine-readable security features do not rely on just one specific security feature. Instead, it is common and indeed advantageous to incorporate multiple covert and / or explicit security features to make it difficult to counterfeit the security feature. Another advantage is the possibility of having multiple authentication techniques, which add layered or alternating covert and / or explicit security features to a security document or article. It is crucial that the multiple security features do not interfere with each other when it comes to detection and authentication.

[0009] However, some ferromagnetic components can interfere with the incorporation of other security features, particularly in terms of potential luminescence and / or IR absorption. This makes it particularly difficult to include luminescent and / or IR absorbing security features, as the sensing technology that identifies the features will ultimately suffer from interference from the ferromagnetic component itself. Therefore, there is a need to incorporate ferromagnetic pigments that are non-luminescent and / or show minimal or no IR absorption while maintaining the possibility of reliably authenticating security documents and / or articles.

[0010] Other aspects that need to be considered are uniform incorporation of the ferromagnetic pigment into the ink composition, thereby providing stability and the ability to incorporate the pigment into a variety of ink compositions and backward compatibility with standard magnetic readers. There is also a need to provide detection and authentication capabilities at low cost using standard off-the-shelf magnetic detection means and the ability to perform detection and authentication operations at long distances and high speeds.

[0011] Thus, there remains a need for stable and reliable security ink compositions that provide strong magnetic detection and authentication capabilities while minimally interfering with the incorporation of additional security features.

[0012] It is therefore an object of the present invention to overcome the drawbacks of the prior art. Summary of the invention

[0013] In one aspect, the present invention relates to a security ink composition comprising at least one non-luminescent undoped Y 3 Fe 5-x M x O 12 Pigments,

[0014] Where x satisfies the following conditions: 0≤x≤1.25;

[0015] M is selected from the group consisting of aluminum, gallium, calcium, and mixtures thereof; and

[0016] wherein after drying and / or curing, at least one machine-readable security feature derived from the application, preferably printing, of the security ink composition has a -12 m 3 The integrated magnetic susceptibility of the material is measured and exhibits ferromagnetic resonance (FMR) characteristics for authentication purposes.

[0017] In another aspect, the invention relates to a machine-readable security feature comprising at least one security ink composition as described herein.

[0018] In yet another aspect, the invention relates to a security document or article comprising at least one machine-readable security feature as described herein.

[0019] In another aspect, the present invention relates to a method for authenticating a security document or article, comprising the steps of:

[0020] a) providing a security document or article comprising at least one machine-readable security feature as described herein;

[0021] b) defining, for the purpose of FMR signal detection, at least one area of ​​the security document or article containing the at least one machine-readable security feature;

[0022] c) detecting and recording an FMR spectrum of at least one machine-readable security feature to provide a recorded FMR spectrum containing sufficient data points to establish at least one FMR characteristic;

[0023] d) parameterizing or directly using the recorded FMR spectra to establish at least one regionally defined FMR characteristic;

[0024] e) comparing the at least one regionally defined FMR characteristic established from step d) with at least one predefined or expected FMR characteristic;

[0025] f) determining the authenticity of the security document or article based on the comparison operation performed under step e). BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The parameterized FMR spectrum (ie the FMR characteristics) in terms of two parameters, line width (at half protrusion) and line center field, is shown. DETAILED DESCRIPTION

[0027] The following definitions may be used to clarify the meaning of terms discussed in the specification and / or defined in the claims.

[0028] As used herein, the indefinite article "a" means one as well as more than one and does not necessarily limit its designated noun to the singular.

[0029] As used herein, the term "about" means that the amount or value in question can be the specified value or some other value nearby. The phrase is intended to convey that similar values ​​within the range of ±5% of the indicated value produce equivalent results or effects according to the present invention.

[0030] As used herein, the term "and / or" or "or / and" means that all or only one of the elements of the group may be present. For example, "A and / or B" should mean "only A, or only B, or both A and B".

[0031] As used herein, the term "at least one" is intended to define one or more than one, for example one or two or three.

[0032] The term "secure document or article" refers to a document or article, respectively, that is typically protected against counterfeiting or fraud by at least one security feature. Examples of secure documents include, but are not limited to, valuable documents and valuable commodities.

[0033] As used herein, the term "undoped" is intended to define the absence of lanthanides from the periodic table. For the sake of clarity, the word "absence" does not exclude the inevitable residual content of lanthanides in negligible amounts.

[0034] As used herein, the term "non-emissive" is intended to define the absence of luminescence of any kind in the visible and IR range in the composition so defined.

[0035] As used herein, a "ferromagnetic resonance (FMR) spectrum" is a recorded spectrum obtained after detecting a signal of at least one security ink (composition) containing ferromagnetic pigments as described herein by suitable magnetic detection means in at least one defined region of a sample. The spectrum may be recorded at a given radio frequency in a magnetic field scan or at a given magnetic field in a radio frequency scan. It is not necessary to detect and record the FMR spectrum over the entire possible range of the field or frequency scan. Therefore, the FMR spectrum of a selected portion of the range may also be recorded, as long as the recorded spectrum provides sufficient data points for establishing at least one FMR characteristic as described herein.

[0036] As used herein, a "ferromagnetic resonance (FMR) characteristic" is a characteristic representation of a recorded FMR spectrum. The recorded FMR spectrum itself can be used directly for authentication purposes, i.e., the recorded spectrum can be used as an FMR characteristic. Alternatively, the FMR spectrum can be parameterized by at least one suitable method. In other words, the FMR spectrum can be used to establish at least one low-dimensional parameter representation, which is derived from a mathematical estimate of the definition parameters of the FMR spectrum for the purpose of authentication. In an exemplary form, the FMR characteristic can be simplified to only 2 parameters, i.e., the line width and line center field of the spectrum mode. For more complex spectra, another suitable FMR characteristic can be obtained by projecting the spectrum onto, for example, a suitable function basis (e.g., by principal component analysis through GramSchmidt orthogonal normalization of several spectra) . As described herein, at least one regionally defined FMR characteristic established is an authentication means for at least one machine-readable security feature, and the at least one regionally defined FMR characteristic established is the FMR spectrum itself or any parameterized form thereof.

[0037] The security ink composition or security ink as described herein comprises at least one non-luminescent undoped Y 3 Fe 5-x M x O 12 The invention relates to a pigment, wherein x satisfies the following conditions: 0≤x≤1.25; and M is selected from the group consisting of aluminum, gallium or calcium and a mixture thereof.

[0038] Y 3 Fe 5-x M x O 12 Yttrium iron garnet pigments are also known in the art as YIG pigments. In the presence of the element M, the pigment may be correspondingly referred to as a YI(M)G pigment. For example, in the presence of aluminum, the pigment is referred to as a YI(Al)G garnet pigment. YI(M)G pigments have a specific crystal structure composition, which is affected by the presence or absence of the element M. These changes in the crystal structure give the pigment different magnetic properties, depending on the value of the element M and x.

[0039] The element M can be freely selected from aluminum, gallium or calcium and mixtures thereof. The choice of a particular M element does not significantly change Y 3 Fe 5-x M x O 12 The FMR characteristic is the detected ferromagnetic distribution of the pigment, ie the pigment is capable of providing at least one characteristic and unique regionally defined FMR property for authentication purposes, independently of the selected element M. In a preferred embodiment, the element M is aluminum.

[0040] Although Y 3 Fe 5-xM x O 12 The pigment may not contain any element M (x=0), but advantageously the pigment contains at least a certain amount of the element M (value of x=0.01). Thus, in the crystal structure, preferably at least a certain amount of Fe is replaced by the element M. Even small amounts of the element M replacing Fe ions in the pigment result in a favorable signal-to-noise ratio and make the detection and authentication of the at least one regionally defined FMR property of the applied, preferably printed, at least one machine-readable security feature easier.

[0041] In a preferred embodiment, Y 3 Fe 5-x M x O 12 The value of x in the system pigment is 0.01≤x≤1.25, more preferably 0.10≤x≤1.25. In an even more preferred embodiment, the value of x is in the range of 0.25≤x≤1.00. The presence of the element M in the above range provides an optimal signal-to-noise ratio and FMR detectability profile for the derived at least one machine-readable security feature.

[0042] Y 3 Fe 5-x M x O 12 The corresponding measure of the replacement of Fe by element M in a pigment can also be described in terms of the mol% replacement of Fe ions by ions of element M in the crystal structure. For example, if the value of x is 0.01, this would translate into a 0.2 mol% replacement of Fe ions by ions of element M in the pigment crystal structure. Considering the maximum value of x = 1.25, this would correspond to a 25 mol% replacement of Fe ions. Thus, in the case of Y 3 Fe 5-x M x O 12 In the pigment system, Fe ions can be advantageously replaced by up to 25 mol%. The higher the substitution amount of element M for Fe, the worse the performance, especially the comprehensive magnetic susceptibility. In a preferred embodiment, the substitution of element M for Fe is between 2 mol% and 20 mol%, or between 5 mol% and 20 mol%.

[0043] Y 3 Fe 5-x M x O 12 The pigment may be incorporated into the security ink composition described herein at up to 40 wt %, up to 30 wt %, or preferably up to 20 wt %, or even up to 15 wt %. Due to the easy detectability of the pigment, only a small amount of the pigment is sufficient to be included in the security ink composition, depending on the type of security ink being formulated.

[0044] In addition, due to the low intrinsic visible color of the pigment itself, the Y 3 Fe 5-x M x O 12 The use of color pigments provides the flexibility to add other color pigments and adjust the color profile of the security ink composition while maintaining detectability and authentication features.

[0045] Y 3 Fe 5-x M x O 12 The pigments can be obtained by synthesis methods known to those skilled in the art, such as mechanical alloying, emulsion coprecipitation, solid state sintering, spray pyrolysis, microwave hydrothermal synthesis and sol-gel synthesis. One of the commonly used synthesis methods is also to calcine a single oxide at high temperature.

[0046] The security ink composition is applied, preferably printed, to provide at least one machine-readable security feature having, after drying and / or curing, a width of at least about 200×10 -12 m 3 The integrated magnetic susceptibility of the material is measured and exhibits ferromagnetic resonance (FMR) characteristics for authentication purposes.

[0047] A minimum level of integrated magnetic susceptibility is important to ensure rapid and reliable detection of security features in, for example, ATM or HSS machines and to provide detectability by common magnetic detectors. When the value of x is between the previously defined ranges, the pigment provides the required integrated magnetic susceptibility characteristics for detection of at least one machine-readable security feature printed, while keeping the amount of pigment used at a fairly small level. This provides the benefit of reduced cost and process efficiency, particularly compared to paramagnetic pigments. When x>1.25, the integrated magnetic susceptibility may not be high enough to ensure reliable detection.

[0048] Authentication of at least one machine-readable security feature comprising a security ink composition is performed by at least one regionally defined FMR characteristic. The FMR characteristic may take the form of a spectrum itself, or alternatively may take the form of at least one mathematically derived parameterization. For the purpose of authenticating at least one machine-readable security feature comprising a single pigment or a blend of pigments, as described herein, it is not necessary that the at least one regionally defined FMR characteristic established is identical to or exactly matches at least one FMR characteristic that is statistically expected or previously recorded. As long as at least one FMR characteristic meets an industry acceptable or minimum confidence / tolerance threshold, the at least one machine-readable security feature may be classified as authentic.

[0049] When a single pigment as described herein is included in a security ink composition, at least one specific and unique FMR characteristic can be derived for the pigment from the recorded FMR spectrum, depending on the element M and its substitution amount. In one form, the FMR characteristic can be parameterized in terms of two parameters, line width and line center field. For example, if the value of x is 1 and the element M is aluminum, then Y 3 Fe 5-x M x O 12 The pigment will have the formula Y 3 Fe 4 AlO 12 . With respect to at least one unique FMR characteristic defined by separate values ​​of line width and line center field, the specific pigment and thereby the derived machine readable security feature can be characterized. However, it is to be noted that this parameterization represents one way of establishing an FMR characteristic for authentication purposes. Other ways of parameterizing the recorded FMR spectrum can also be used, i.e. more than 2 parameters can be derived to establish the FMR characteristic, depending on the parameterization method or different parameterization methods can be used. It is also possible to use multiple parameterization methods in combination with each other. This allows the possibility to develop a set of complex characteristics for at least one machine readable security feature, thereby broadening the set for authentication purposes.

[0050] In another embodiment, 2 kinds of pigments as described herein, i.e., blends, can be included in the security ink composition. In this case, 2 kinds of pigments will provide 2 separate FMR spectra. 2 spectra can be combined into a commonly recorded FMR spectrum, representing the blend of pigments. The individual characteristics of the mixture and thus the common FMR spectrum depend on the substituted element M, the substitution amount x in each pigment and the amount of pigment in the mixture. As mentioned above for a single pigment, the recorded common FMR spectrum itself or at least one parameterized form of the FMR spectrum can be further used. As long as the FMR characteristics of the blend are different from the characteristics of the individual pigments, it can be used as the basis for authentication purposes.

[0051] In yet another embodiment, the additional non-emissive undoped Y 3 Fe 5-x M x O 12 A further pigment may be included in the security ink composition, wherein x satisfies the following conditions: 0≤x≤5, preferably 0≤x≤4.99, and M is selected from the group consisting of: aluminum, gallium or calcium and mixtures thereof. The further pigment also exhibits at least one FMR property specific to itself, the at least one FMR property being characteristic of the further pigment. As previously mentioned, at least one regionally defined FMR property for authentication purposes of such a mixture may also be derived.

[0052] Y 3Fe 5-x M x O 12 The pigments can be incorporated into a variety of ink compositions. Therefore, the pigments provide a wide range of flexibility for incorporation into many types of ink compositions. Since the pigments provide a strong signal, they can be incorporated in lower amounts and will not negatively affect the uniformity and applicability of the security ink composition.

[0053] Although the security ink composition may be applied in methods other than printing (e.g. coating, spraying, extrusion), the security ink described herein is particularly suitable for application to substrates such as those described herein by a printing method selected from the group consisting of an offset printing method, a gravure printing method, a screen printing method, a rotogravure printing method, a flexographic printing method and an inkjet printing (particularly flexographic inkjet printing) method, more preferably selected from the group consisting of a gravure printing method and a screen printing method.

[0054] The safety ink described herein is an oxidative drying safety ink, a UV-Vis curable safety ink, a thermal drying safety ink or a combination thereof. However, the skilled person can well formulate the pigment into other kinds of ink compositions.

[0055] Oxidative drying safety inks dry by oxidation in the presence of oxygen, particularly in the presence of atmospheric oxygen. During the drying process, the oxygen combines with one or more components of the ink to convert the ink into a solid state. The oxidative drying gravure inks described herein contain one or more desiccants (also referred to in the art as catalysts, siccatives, siccative agents, desiccatives or dessicators) to accelerate the oxidation process. Examples of desiccants include inorganic or organic salts of one or more metals, metal soaps of organic acids, metal complexes and metal complex salts. Suitable salts of one or more metals include salts containing cobalt, calcium, copper, zinc, iron, zirconium, manganese, barium, zinc, strontium, lithium, vanadium and potassium as one or more cations, and halides, nitrates, sulfates, carboxylates such as acetates, ethylhexanoates, octoates and naphthenates, or acetylacetonates as one or more anions, such as, for example, ethylhexanoates of cobalt, manganese and zirconium. Suitable examples of metal complexes and metal complex salts include manganese, vanadium and iron compounds (i.e., manganese complexes, manganese complex salts, vanadium complexes, vanadium complex salts, iron complexes and iron complex salts). When present, one or more driers for the oxidatively drying intaglio inks described herein are preferably present in a total amount of about 0.01 wt % to about 10 wt %, more preferably in a total amount of about 0.1 wt % to about 5 wt %, the weight percentages being based on the total weight of the oxidatively drying intaglio ink.

[0056] It is known in the art that oxidative drying offset printing security inks require high viscosity. Typically, security inks suitable for oxidative drying offset printing processes are heated to 40°C and 1000s -1 The compositions have viscosities in the range of about 2.5 to about 25 Pa s; viscosities measured on a Haake Roto-Visco RV1 with a 2 cm, 0.5° cone.

[0057] As is generally known in the art, the oxidative drying safe ink comprises one or more varnishes. The term "varnish" is also referred to in the art as a resin, a binder or an ink carrier. The drying varnish described herein is preferably present in the oxidative drying safe ink described herein in an amount of about 10 to about 90% by weight, the weight percentage being based on the total weight of the oxidative drying safe ink. As is generally known in the art, one or more varnishes used for the oxidative drying safe ink described herein are preferably selected from the group consisting of polymers comprising unsaturated fatty acid residues, saturated fatty acid residues and mixtures thereof. Preferably, the one or more varnish oxidative drying safe inks described herein comprise unsaturated fatty acid residues to ensure air drying properties. Particularly preferred oxidative drying varnishes are resins comprising unsaturated acid groups, and even more preferred are resins comprising unsaturated carboxylic acid groups. However, the resin may also comprise saturated fatty acid residues. Preferably, the varnish oxidative drying safe ink described herein comprises acid groups, i.e. the oxidative drying varnish is selected from acid-modified resins. The oxidative drying varnish described herein may be selected from the group consisting of alkyd resins, vinyl polymers, polyurethane resins, hyperbranched resins, rosin-modified maleic resins, rosin-modified phenolic resins, rosin esters, petroleum resin-modified rosin esters, petroleum resin-modified alkyd resins, alkyd resin-modified rosin / phenolic resins, alkyd resin-modified rosin esters, acrylic-modified rosin / phenolic resins, acrylic-modified rosin esters, urethane-modified rosin / phenolic resins, urethane-modified rosin esters, urethane-modified alkyd resins, epoxy-modified rosin / phenolic resins, epoxy-modified alkyd resins, terpene resins, nitrocellulose resins, polyolefins, polyamides, acrylic resins, and combinations or mixtures thereof. Polymers and resins are used interchangeably herein.

[0058] Saturated and unsaturated fatty acid compounds can be obtained from natural and / or artificial sources. Natural sources include animal and / or plant sources. Animal sources can include animal fat, milk fat, fish oil, lard, liver fat, tuna oil, sperm whale oil and / or beef and sheep oil. Plant sources can include oils, such as vegetable oils and / or non-vegetable oils. Examples of vegetable oils include, but are not limited to, bitter melon, Borage, Marigold, rapeseed (canola), castor, Chinese wood, coconut, conifer seeds, corn, cottonseed, dehydrated castor, linseed, grape seeds, jacaranda seeds, linseed oil, palm, palm kernel, peanut, pomegranate seeds, rapeseed, safflower, snake melon, soybean (bean), sunflower, tall, tung oil and wheat germ. Artificial sources include distilled tall oil (tail oil) and / or chemical or biochemical synthesis methods. Suitable fatty acids also include myristic acid (C 14 H 26 O 2 , CAS No. 544-64-9), palmitic acid (C 16 H 30 O 2 , CAS No. 373-49-9), oleic acid (C 18 H 34 O 2 , CAS No. 112-80-1), α-eleostearic acid (C 18 H 30 O 2 , CAS No. 506-23-0), licanic acid (C 18 H 28 O 3 , CAS No. 623-99-4), linoleic acid (C 18 H 32 O 2 , CAS No. 60-33-3), linolenic acid (C 18 H 30 O 2 , CAS No. 463-40-1), linoleic acid (C 18 H 28 O 2 , CAS No. 20290-75-9), arachidonic acid (C 20 H 32 O 2 , CAS No. 506-32-1), ricinoleic acid (C 18 H 34 O 3 , CAS No. 141-22-0), erucic acid (C 22 H 42 O 2, CAS No. 112-86-7), gadoleic acid (C 20 H 38 O 2 , CAS No. 29204-02-2), clupanodonic acid (C 22 H 34 O 2 , CAS No. 24880-45-3), nisinic acid (C 24 H 36 O 2 , CAS No. 68378-49-4) and mixtures thereof. Those fatty acids are usually used in the form of mixtures of fatty acids derived from natural or synthetic oils.

[0059] The oxidative drying safety ink described herein may further comprise one or more antioxidants, such as those known to those skilled in the art. Suitable antioxidants include, but are not limited to, alkylphenols, hindered alkylphenols, alkylthiomethylphenols, eugenol, secondary amines, thioethers, phosphites, phosphonites, dithiocarbamates, gallates, malonates, propionates, acetates and other esters, carboxamides, hydroquinones, ascorbic acid, triazines, benzyl compounds, and tocopherol and terpene analogs. Such antioxidants are commercially available, for example, from sources disclosed in WO 02 / 100 960. Hindered alkylphenols are phenols having at least one or two alkyl groups ortho to the phenolic hydroxyl group. One, preferably two alkyl groups ortho to the phenolic hydroxyl group are preferably secondary or tertiary alkyl groups, most preferably tertiary alkyl groups, particularly tert-butyl, tert-amyl or 1,1,3,3-tetramethylbutyl. Preferred antioxidants are hindered alkylphenols, and in particular 2-tert-butyl-hydroquinone, 2,5-di-tert-butyl-hydroquinone, 2-tert-butyl-p-cresol and 2,6-di-tert-butyl-p-cresol. When present, one or more antioxidants are present in an amount of about 0.05 to about 3 weight percent, the weight percent being based on the total weight of the oxidatively drying safe ink.

[0060] The oxidatively drying safety ink described herein may further comprise one or more waxes preferably selected from the group consisting of synthetic waxes, petroleum waxes and natural waxes. Preferably, the one or more waxes are selected from the group consisting of microcrystalline waxes, paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, Fischer-Tropsch waxes, silicone oils, beeswax, candelilla wax, montan wax, carnauba wax and mixtures thereof. When present, the one or more waxes are preferably present in an amount of about 0.1 to about 15 weight percent, the weight percent being based on the total weight of the oxidatively drying safety ink.

[0061] According to one embodiment, the oxidatively drying security ink described herein is an oxidatively drying gravure security ink, wherein the oxidatively drying gravure security ink comprises one or more driers described herein, one or more varnishes described herein and optional additives or ingredients described herein.

[0062] At least one machine-readable security feature described herein can preferably be prepared by an intaglio printing method (also known in the art as engraved copperplate printing and engraved steel mold printing), which is capable of depositing a sufficiently high amount of machine-readable material on a substrate to allow its detection and sensing. An intaglio printing method refers to a printing method and process particularly used in the field of valuable documents. The intaglio printing method is known to be the most consistent and high-quality printing method for producing fine tapered lines, and is therefore the printing technology selected for fine designs in the field of security documents, especially banknotes and stamps. In particular, one of the distinguishing features of the intaglio printing method is that the layer thickness of the ink transferred to the substrate can vary from a few microns to tens of microns by using corresponding shallow or deep engravings on the intaglio printing device. As described above, therefore, the layer thickness of the intaglio printing security feature allows a sufficiently high amount of material on the substrate for its detection and sensing.

[0063] It is known in the art that gravure inks or in particular oxidative drying gravure security inks require high viscosity. Typically, security inks suitable for (oxidative drying) gravure printing processes are tested at 40°C and 1000 s using a Haake Roto-Visco RV1 rotational rheometer. -1 The rotational rheometer used a cone-plate having a diameter of 20 mm and a 0.5° geometry, cut off at 25 μm, with a viscosity in the range of about 3 to about 60 Pa s.

[0064] The oxidative drying gravure printing security ink described herein may further comprise one or more surfactants, in particular hydrophilic macromolecular surfactants, such as those described in EP 0 340 163 B1. The role of the optional surfactant is to help wipe off the excess ink present on the printing cylinder immediately before the printing cylinder contacts the substrate. The process of wiping off the excess ink is part of any high-speed industrial gravure printing process and is carried out using a paper towel or paper roll ("calico") or a polymer wiping the cylinder and a clean aqueous solution ("wiping solution"). In this case, the optional surfactant is used to emulsify the excess ink in the cleaning solution. The surfactant may be a nonionic, anionic or cationic and zwitterionic surfactant. In the case of a hydrophilic macromolecular surfactant, the functional group is, for example, a carboxylic acid group or a sulfonic acid group, a hydroxyl group, an ether group, or a primary, secondary, tertiary or quaternary amino group. The acid group can be neutralized with an amine, an alcanolamine or preferably an inorganic base or a combination thereof. The primary, secondary and tertiary amino groups can be neutralized with inorganic or organic acids such as sulfonic acid, formic acid, acetic acid, trifluoroacetic acid, etc. Particularly preferred are anionic macromolecular surfactants (AMS), such as those described in EP 2014 729 A1.

[0065] The UV-Vis curable safety ink is composed of a safety ink that can be cured under UV-Vis light radiation. The UV-Vis curable safety ink described herein contains about 0.1 wt % to about 20 wt % of one or more photoinitiators, and preferably about 1 wt % to about 15 wt %, the weight percentages being based on the total weight of the UV-Vis curable safety ink.

[0066] Preferably, the UV-Vis curable security ink described herein comprises one or more UV curable compounds, which are monomers and oligomers selected from the group consisting of free radical curable compounds and cationic curable compounds. The security ink described herein may be a mixed system and comprises a mixture of one or more cationic curable compounds and one or more free radical curable compounds. Cationic curable compounds are cured by a cationic mechanism, which generally includes activation by irradiation of one or more photoinitiators, which release cationic substances such as acids, which in turn initiate curing so as to react and / or crosslink the monomers and / or oligomers, thereby curing the security ink. Free radical curable compounds are cured by a free radical mechanism, which generally includes activation by irradiation of one or more photoinitiators, thereby generating free radicals, which in turn initiate polymerization, so that the security ink is cured.

[0067] Preferably, the UV-Vis curable security ink described herein comprises one or more oligomers (also referred to as prepolymers in the art) selected from the group consisting of: oligomeric (meth)acrylates, vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, oxetanes, tetrahydrofurans, lactones, cyclic thioethers, vinyl and propenyl thioethers, hydroxyl-containing compounds and mixtures thereof. More preferably, the binder of the UV-Vis curable security ink described herein is prepared from an oligomer selected from the group consisting of: oligomeric (meth)acrylates, vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, oxetanes, tetrahydrofurans, lactones and mixtures thereof. Typical examples of epoxides include, but are not limited to, glycidyl ethers, β-methyl glycidyl ethers of aliphatic or cycloaliphatic diols or polyols, glycidyl ethers of diphenols and polyphenols, glycidyl esters of polyphenols, 1,4-butanediol diglycidyl ether of phenol formaldehyde novolac, resorcinol diglycidyl ethers, alkyl glycidyl ethers, copolymers containing acrylic esters (e.g., styrene-glycidyl methacrylate or methyl methacrylate-acrylic acid esters), The present invention relates to glycidyl ethers of bisphenol A and bisphenol F epoxy resins. ...Examples of vinyl ethers include, but are not limited to, triethylene glycol divinyl ether, 1,4-cyclohexanedimethanol divinyl ether, 4-hydroxybutyl vinyl ether, propenyl ether of propylene carbonate, dodecyl vinyl ether, tert-butyl vinyl ether, tert-amyl vinyl ether, cyclohexyl vinyl ether, 2-ethylhexyl vinyl ether, ethylene glycol monovinyl ether, butanediol monovinyl ether, hexanediol monovinyl ether, 1,4-cyclohexanedimethanol monovinyl ether, diethylene glycol monovinyl ether, ethylene glycol divinyl ether, ethylene glycol butyl ...butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl The present invention relates to hydroxyl-containing compounds, such as hydroxyl-containing compounds, vinyl ethers, butane-1,4-diol divinyl ether, hexanediol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, triethylene glycol methyl vinyl ether, tetraethylene glycol divinyl ether, pluriol-E-200 divinyl ether, polytetrahydrofuran divinyl ether-290, trimethylolpropane trivinyl ether, dipropylene glycol divinyl ether, octadecyl vinyl ether, (4-cyclohexyl-methyleneoxyethylene)-methyl glutarate and (4-butoxyethylene)-iso-phthalate. Examples of hydroxyl-containing compounds include, but are not limited to, polyester polyols, such as, for example, polycaprolactones or polyester adipate polyols, glycols and polyether polyols, castor oil, hydroxyl-functional vinyl and acrylic resins, such as cellulose esters such as cellulose acetate butyrate and phenoxy resins. Further examples of suitable cationic curable compounds are disclosed in EP 2125713 B1 and EP 0119425 B1.

[0068] According to one embodiment of the present invention, the UV-Vis curable security ink described herein comprises one or more free radical curable oligomeric compounds selected from (meth)acrylates, preferably selected from the group consisting of epoxy (meth)acrylates, (meth)acrylated oils, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, silicone (meth)acrylates, amino (meth)acrylates, acrylic (meth)acrylates and mixtures thereof. The term "(meth)acrylate" in the context of the present invention refers to acrylates as well as the corresponding methacrylates. The components of the UV-Vis curable security inks described herein can be prepared with additional vinyl ethers and / or monomer acrylates, such as, for example, trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PTA), tripropylene glycol diacrylate (TPGDA), dipropylene glycol diacrylate (DPGDA), hexanediol diacrylate (HDDA) and their polyethoxylated equivalents, such as, for example, polyethoxylated trimethylolpropane triacrylate, polyethoxylated pentaerythritol triacrylate, polyethoxylated tripropylene glycol diacrylate, polyethoxylated dipropylene glycol diacrylate and polyethoxylated hexanediol diacrylate.

[0069] Alternatively, the UV-Vis curable security ink described herein is a hybrid ink and may be prepared from a mixture of free radical curable compounds and cationically curable compounds such as those described herein.

[0070] As mentioned above, UV-Vis curing of monomers, oligomers requires the presence of one or more photoinitiators and can be achieved in a variety of ways. As mentioned herein and known to those skilled in the art, the UV-Vis curable security ink described herein to be cured and hardened on a substrate comprises one or more photoinitiators as described herein, with one or more photosensitizers optionally selected according to its / their absorption spectrum related to the emission spectrum of the radiation source. Depending on the degree of transmission of electromagnetic radiation through the substrate, hardening of the security ink can be obtained by increasing the irradiation time. However, depending on the substrate material, the irradiation time is limited by the substrate material and its sensitivity to the heat generated by the radiation source.

[0071] Depending on the monomer, oligomer or prepolymer used in the UV-Vis curable security ink described herein, different photoinitiators can be used. Suitable examples of free radical photoinitiators are known to those skilled in the art and include, but are not limited to, acetophenones, benzophenones, benzyl dimethyl ketals, α-amino ketones, α-hydroxy ketones, phosphine oxides and phosphine oxide derivatives, and mixtures of two or more thereof. Examples of cationic photoinitiators are known to those skilled in the art and include, but are not limited to, onium salts, such as organic iodonium salts (e.g., diaryl iodonium salts), oxonium salts (e.g., triaryl oxonium salts) and sulfonium salts (e.g., triaryl sulfonium salts), and mixtures of two or more thereof. Other examples of useful photoinitiators can be found in standard textbooks such as "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", Volume III, "Photoinitiators for Free Radical Cationic and Anionic Polymerization", 2nd edition, by JV Crivello & K. Dietliker, edited by G. Bradley, published in 1998 by John Wiley & Sons and SITA Technology Limited. In order to achieve effective curing, it is also advantageous to include a sensitizer in combination with more than one photoinitiator. Typical examples of suitable photosensitizers include, but are not limited to, isopropyl thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX) and 2,4-diethyl-thioxanthone (DETX), and mixtures of two or more thereof.

[0072] The UV-Vis curable safety ink described herein is preferably a UV-Vis curable offset printing safety ink, a UV-Vis curable gravure printing safety ink, a UV-Vis curable screen printing safety ink, a UV-Vis curable flexographic printing safety ink, a UV-Vis curable rotary gravure printing safety ink or a UV-Vis curable inkjet printing safety ink (especially a flexographic inkjet printing safety ink), and is more preferably a UV-Vis curable gravure printing safety ink, a UV-Vis curable screen printing safety ink, a UV-Vis curable flexographic printing safety ink, a UV-Vis curable rotary gravure printing safety ink or a UV-Vis curable flexographic inkjet printing safety ink.

[0073] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable offset printing security ink, wherein the UV-Vis curable offset printing security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein and optional additives or ingredients described herein.

[0074] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable gravure security ink, wherein the UV-Vis curable gravure security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein and optional additives or ingredients described herein.

[0075] It is known in the art that UV-Vis curable offset printing security inks require high viscosity. Typically, security inks suitable for UV-Vis curable printing methods are heated to 40°C and 1000s -1 The compositions have viscosities in the range of about 2.5 to about 25 Pa s; viscosities measured on a Haake Roto-Visco RV1 with a 2 cm, 0.5° cone.

[0076] It is known in the art that UV-Vis curable gravure security inks require high viscosity. Typically, security inks suitable for gravure printing processes are tested at 40°C and 1000 s using a Haake Roto-Visco RV1 rotational rheometer. -1 The rotational rheometer typically has a viscosity in the range of about 3 to about 60 Pa s using a cone-plate having a diameter of 20 mm and a 0.5° geometry, cut off at 25 μm.

[0077] Examples of UV-Vis curable gravure security inks are described in WO 2021 / 018771 A1, the disclosure of which is incorporated herein by reference.

[0078] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable screen printing security ink, wherein the UV-Vis curable screen printing security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein, and optional additives or ingredients described herein.

[0079] Screen printing (screen printing) (also referred to as silk screen printing in the art) is a template method whereby ink is transferred to a surface through a template, which is supported by a fine fabric mesh of silk, synthetic fibers or metal wires stretched on a frame. The holes of the mesh are blocked in the non-image area and remain open in the image area, and the image carrier is referred to as a screen. Screen printing can be flat printing or rotary printing. During printing, ink is supplied to the frame, the ink accumulates above the screen, and then a scraper is pulled through the screen, thereby forcing the ink to pass through the openings of the screen. At the same time, the surface to be printed is kept in contact with the screen, and the ink is transferred to the surface to be printed. Screen printing is further described, for example, in The Printing ink manual, RHLeach and RJPierce, Springer Edition, 5th edition, pages 58-62, and Printing Technology, JMAdams and PADolin, Delmar Thomson Learning, 5th edition, pages 293-328.

[0080] It is known in the art that screen printing or in particular UV-Vis curable screen printing security inks require low viscosity. Typically, using a Brookfield machine (model "DV-IPrime", small sample adapter, spindle S27 at 100 or 50 rpm), security inks suitable for screen printing methods have a viscosity in the range of about 0.05 to about 5 Pa s at 25°C.

[0081] Various suitable screen printing ink compositions are described in WO 2021 / 175907 A1 and WO 2020 / 169316 A1, the disclosures of which are incorporated herein by reference. Particularly suitable screen printing ink compositions are based on mixtures (cationic / radical), free radical curing mechanisms and solvent systems.

[0082] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable flexographic security ink, wherein the UV-Vis curable flexographic security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein and optional additives or ingredients described herein.

[0083] The flexographic printing process preferably uses a unit having a chambered doctor blade, an anilox roller and a plate cylinder. The anilox roller advantageously has small cells, whose volume and / or density determine the rate of application of the protective varnish. The chambered doctor blade rests on the anilox roller, filling the cells while scraping off excess protective varnish. The anilox roller transfers the ink to the plate cylinder, which ultimately transfers the ink to the substrate. The plate cylinder can be made of polymer or elastomeric material. Polymers are mainly used as photopolymers in the plate and sometimes as seamless coatings on the sleeve. Photopolymer plates are made of photosensitive polymers that are hardened by ultraviolet (UV) light. The photopolymer plate is cut to the desired size and placed in a UV exposure unit. One side of the plate is fully exposed to UV light to harden or cure the base of the plate. The plate is then turned over, the negative of the job is mounted on the uncured side, and the plate is further exposed to UV light. This hardens the plate in the image area. The plate is then treated to remove the unhardened photopolymer from the non-image areas, which reduces the plate surface in these non-image areas. After treatment, the plate is dried and given a post-exposure dose of UV light to cure the entire plate. The preparation of plate cylinders for flexographic printing is described in: Printing Technology, JM Adams and PADolin, Delmar Thomson Learning, 5th edition, pages 359-360.

[0084] It is known in the art that UV-Vis curable flexographic security inks require low viscosity. Typically, security inks suitable for flexographic printing processes are measured at 25°C and 1000 s using a rotational viscometer DHR-2 from TA Instruments (cone-plane geometry, 40 mm diameter). -1 The composition has a viscosity in the range of about 0.01 to about 1 Pa s.

[0085] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable rotogravure security ink, wherein the UV-Vis curable rotogravure security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein and optional additives or ingredients described herein.

[0086] As is known to the person skilled in the art, the term "rotogravure" refers to a printing method as described, for example, in "Handbook of print media", Helmut Kipphan, Springer Edition, page 48. Rotogravure is a printing method in which image elements are engraved in the surface of a cylinder. The non-image areas are at a constant original level. Before printing, the entire printing plate (non-printing and printing elements) is inked and filled with ink. Before printing, the ink is removed from the non-image by a wiper or a doctor blade so that the ink remains only in the cells. The image is transferred from the cells to the substrate by a pressure, typically in the range of 2-4 bars, and by adhesion forces between substrate and ink. The term "rotogravure" does not include gravure printing methods (also known in the art as engraved steel mold or copperplate printing methods), which rely, for example, on different kinds of inks.

[0087] It is known in the art that UV-vis curable rotogravure security inks have low viscosity. Typically, security inks suitable for the rotogravure printing process are measured at 25°C and 1000 s using a rotational viscometer DHR-2 from TA Instruments (cone plane geometry, 40 mm diameter). -1 The composition has a viscosity in the range of about 0.01 to about 0.5 Pa s.

[0088] According to one embodiment, the UV-Vis curable security ink described herein is a UV-Vis curable flextensional inkjet printing security ink, wherein the UV-Vis curable flextensional inkjet printing security ink comprises one or more photoinitiators described herein, one or more UV curable compounds are monomers and oligomers described herein and optional additives or ingredients described herein.

[0089] Flextensional inkjet printing is inkjet printing using a flextensional inkjet printhead structure. Typically, a flextensional transducer comprises a body or substrate, a flexible membrane having an orifice defined therein, and an actuator. The substrate defines a reservoir for holding a supply of a fluid material, and the flexible membrane has a circumferential edge supported by the substrate. The actuator may be piezoelectric (i.e., it comprises a piezoelectric material that deforms when a voltage is applied) or thermally activated, as described, for example, in US 8226213. Thus, when the material of the actuator is deformed, the flexible membrane deflects, causing a quantity of fluid material to be ejected from the reservoir through the orifice. A flextensional printhead structure is described in US 5828394, in which a fluid ejector is disclosed, the fluid ejector comprising a wall comprising a thin elastic membrane having an orifice defining a nozzle and an element responsive to an electrical signal, the electrical signal being used to deflect the membrane to eject a drop of fluid from the nozzle. A flexure printhead structure is described in US 6394363, which discloses the use of, for example, excitation of a surface layer incorporating nozzles, the nozzles being arranged above a surface layer having addressability to form a liquid projection array capable of operating at high frequencies with various liquids. A flexure printhead structure is also described in US 9517622, ​​which describes a droplet forming device comprising a membrane member configured to vibrate so as to eject a liquid held in a liquid holding unit, wherein the nozzle is formed in the membrane member. In addition, a vibration unit is provided to vibrate the membrane member; and a drive unit to selectively apply an ejection waveform and an agitation waveform to the vibration unit. A flexure printhead structure is also described in US 8,226,213, which describes a method of braking a thermal bending actuator having an active beam fused to a passive beam. The method includes passing an electric current through the active beam so as to cause thermoelastic expansion of the active beam relative to the passive beam and bending of the actuator.

[0090] It is known in the art that UV-Vis curable flextensional inkjet security inks have very low viscosities. Typically, when using a rotational viscometer DHR-2 from TA Instruments with cone-plane geometry and a diameter of 40 mm at 25°C and 1000 s -1 Security inks suitable for use in flexographic inkjet printing processes have a viscosity of less than about 100 mPa s when measured at .

[0091] Thermal or heat drying security inks consist of security inks that are dried by hot air, infrared rays, or a combination thereof. Thermal drying security inks typically consist of about 10% to about 90% by weight of solids content remaining on the printed substrate and about 10% to about 90% by weight of one or more solvents evaporated due to drying, the one or more solvents being selected from the group consisting of organic solvents, water, and mixtures thereof.

[0092] Preferably, the organic solvent described herein is selected from the group consisting of alcohols (such as ethanol), ketones (such as methyl ethyl ketone), esters (such as ethyl acetate or propyl acetate), glycol ethers (such as DOWANOL TM DPM), glycol ether esters (such as butylene acetate) and mixtures thereof.

[0093] According to one embodiment, the heat-drying safety ink described herein is composed of an aqueous heat-drying safety ink, which contains one or more resins selected from the group consisting of polyester resins, polyether resins, polyurethane resins (e.g., carboxylated polyurethane resins), polyurethane alkyd resins, polyurethane-acrylate resins, polyacrylate resins, polyether polyurethane resins, styrene acrylate resins, polyvinyl alcohol resins, poly(ethylene glycol) resins, polyvinyl pyrrolidone resins, polyethyleneimine resins, modified starches, cellulose esters or ethers (e.g., cellulose acetate and carboxymethyl cellulose), copolymers thereof, and mixtures thereof.

[0094] According to one embodiment, the heat-drying safety ink described herein is composed of a solvent-based heat-drying safety ink, and the solvent-based heat-drying safety ink contains one or more resins selected from the group consisting of: nitrocellulose, methyl cellulose, ethyl cellulose, cellulose acetate, polyvinyl butyral, polyurethane, polyacrylate, polyamide, polyester, polyvinyl acetate, rosin-modified phenolic resin, phenolic resin, maleic resin, styrene-acrylic resin, polyketone resin, and mixtures thereof.

[0095] Suitable heat-drying safety ink compositions are described in WO 2020 / 239740 A1 and WO 2019 / 219250 A1, the disclosures of which are incorporated herein by reference.

[0096] As mentioned above, dual-cure or dual-hardening security inks may be used for printing at least one machine-readable security feature described herein, wherein these security inks combine 2 drying or curing mechanisms.

[0097] Examples of dual-cure or dual-hardening security inks include oxidative drying mechanisms and UV-Vis curing mechanisms, such as for example gravure security inks, for example as described in EP 2 171 007 B1.

[0098] Examples of dual-cure or dual-hardening security inks include oxidative drying mechanisms and thermal drying mechanisms, such as, for example, screen printing security inks, rotogravure printing security inks, and flexographic inkjet printing security inks.

[0099] Examples of dual-cured or dual-hardened security inks include a UV-Vis curing mechanism and a thermal drying mechanism, such as, for example, screen printing security inks and rotogravure printing inks. Typically, these dual-cured or dual-hardened security inks are similar to UV-Vis curable security inks, but include a volatile portion consisting of water and / or one or more organic solvents. These volatile components are first evaporated using hot air and / or an IR dryer, and then UV-Vis curing completes the curing process. The composition of such inks is described, for example, in WO2019 / 002046 A1.

[0100] The security ink or security ink composition described herein may further comprise one or more fillers and / or extenders, wherein the fillers and / or extenders are preferably selected from the group consisting of talc, mica (e.g. muscovite), montmorillonite, bentonite, wollastonite, halloysite, calcined clay, china clay, carbonates (e.g. calcium carbonate, magnesium carbonate), silicates (e.g. magnesium silicate, aluminum silicate), vermiculite, amorphous silica (e.g. fumed silica, precipitated silica, silica powder), wood flour (sawdust), natural fibers, synthetic fibers (e.g. carbon fibers or carbon nanotubes) and mixtures thereof; preferably selected from the group consisting of talc, mica, wollastonite, calcined clay, carbonates, amorphous silica and mixtures thereof.

[0101] When present in a gravure ink, the one or more fillers or extenders are preferably present in a total amount of about 0.1 wt % to about 50 wt %, more preferably about 20 wt % to about 40 wt %, based on the total weight of the oxidatively dried gravure ink. When present in a rotogravure ink, a flexographic ink, or a screen printing ink, the one or more fillers or extenders are preferably present in a total amount of about 0.05 wt % to about 20 wt %, more preferably about 0.1 wt % to about 10 wt %, even more preferably between about 0.5 wt % and about 5 wt %, based on the total weight of the rotogravure ink, the flexographic ink, or the screen printing ink.

[0102] The security ink described herein may further comprise one or more coloring components selected from the group consisting of optically variable pigments, color constant pigments, color constant dyes and mixtures thereof, preferably selected from the group consisting of color constant organic pigments, color constant inorganic pigments and mixtures thereof.

[0103] Dyes suitable for use in the security ink composition are known in the art and are preferably selected from the group comprising reactive dyes, direct dyes, anionic dyes, cationic dyes, acid dyes, basic dyes, food dyes, metal complex dyes, solvent dyes and mixtures thereof. Typical examples of suitable dyes include, but are not limited to, coumarins, cyanines, oxazines, sodium fluorescein, phtalocyanines, indolinocyanines, triphenylmethanes, naphtalocyanines, indolenaphthol-metal dyes, anthraquinones, anthrapyridones, azo dyes, rhodamines, squarilium dyes, croconium dyes. Typical examples of dyes suitable for use in the present invention include, but are not limited to, CI Acid Yellow 1, 3, 5, 7, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 54, 59, 61, 70, 72, 73, 75, 76, 78, 79, 98, 99, 110, 111, 121, 127, 131, 135, 142, 157, 162, 164, 165, 194, 204, 236, 245; CI Direct Yellow 1, 8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 106, 107, 110, 132, 142, 144; CI Basic Yellow 13, 28, 65; CI Active Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42; CI Food Yellow 3, 4; C I Acid Orange 1, 3, 7, 10, 20, 76, 142, 144; CI Basic Orange 1, 2, 59; CI Food Orange 2; CI Orange B; CI Acid Red 1, 4, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 73, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 1 29, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211, 215, 219, 221, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, 357, 359; CI Basic Red 1, 2, 14, 28; CIDirect Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, 253; CI Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43 3, 45, 46, 49, 50, 58, 59, 63, 64, 108, 180; CI Food Red 1, 7, 9, 14; CI Acid Blue 1, 7, 9, 15, 20, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 193, 199, 203, 204, 205, 229, 234, 236, 249, 254, 285; CI basic blue 1, 3, 5, 7, 8, 9, 11, 55, 81; CI direct blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248 , 249; CI Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 46, 77; CI Food Blue 1, 2; CI Acid Green 1, 3, 5, 16, 26, 104; CI Basic Green 1, 4; CI: Food Green 3; CI Acid Violet 9, 17, 90, 102, 121; CI Basic Violet 2, 3, 10, 11, 21; CI Acid Brown 101, 103, 165, 266, 268, 355, 357, 365, 384; CI Basic Brown 1; CIAcid Black 1, 2, 7, 24, 26, 29, 31, 48, 50, 51, 52, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 191, 194; CI Direct Black 17, 19, 22, 32, 39, 51, 56, 62, 7 1, 74, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133, 146, 154, 168; CI Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 18, 31; CI Food Black 2; CI Solvent Yellow 19, CI Solvent Orange 45, CI Solvent Red 8, CI Solvent Green 7, CI Solvent Blue 7, CI Solvent Black 7; CI Disperse Yellow 3, CI Disperse Red 4, 60, CI Disperse Blue 3, and metal azo dyes disclosed in US 5,074,914, US 5,997,622, US 6,001,161, JP 02-080470, JP 62-190272, JP 63-218766. Suitable dyes for use in the present invention may be infrared absorbing dyes or luminescent dyes. When present, one or more dyes described herein are preferably present in a total amount of about 1 wt % to about 20 wt %, the weight percentages being based on the total weight of the security ink composition.

[0104] Typical examples of organic and inorganic pigments include, but are not limited to, CI Pigment Yellow 12, CI Pigment Yellow 42, CI Pigment Yellow 93, CI Pigment 109, CI Pigment Yellow 110, CI Pigment Yellow 147, CI Pigment Yellow 173, CI Pigment Orange 34, CI Pigment Orange 48, CI Pigment Orange 49, CI Pigment Orange 61, CI Pigment Orange 71, CI Pigment Orange 73, CI Pigment Red 9, CI Pigment Red 22, CI Pigment Red 23, CI Pigment Red 67, CI Pigment Red 122, CI Pigment Red 13, CI Pigment Red 143, CI Pigment Red 144, CI Pigment Red 145, CI Pigment Red 146, CI Pigment Red 147, CI Pigment Yellow 148, CI Pigment Orange 149, CI Pigment Orange 61, CI Pigment Orange 71, CI Pigment Orange 73, CI Pigment Red 9, CI Pigment Red 22, CI Pigment Red 23, CI Pigment Red 67, CI Pigment Red 122, CI Pigment Red 147, CI Pigment Yellow 173, CI Pigment Orange CI Pigment Red 144, CI Pigment Red 146, CI Pigment Red 170, CI Pigment Red 177, CI Pigment Red 179, CI Pigment Red 185, CI Pigment Red 202, CI Pigment Red 224, CI Pigment Brown 6, CI Pigment Brown 7, CI Pigment Red 242, CI Pigment Red 254, CI Pigment Red 264, CI Pigment Brown 23, CI Pigment Blue 15, CI Pigment Blue 15:3, CI Pigment Blue 60, CI Pigment Violet 19, CI Pigment Violet 23, CI Pigment Violet 32, CI Pigment Violet 37, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Black 7, CI Pigment Black 11, Pigment Black 31, Pigment Black 32, CI Pigment White 4, CI Pigment White 6, CI Pigment White 7, CI Pigment White 21, CI Pigment White 22, Antimony Yellow, Lead Chromate, Lead Chromate Sulfate, Lead Molybdate, Ultramarine, Cobalt Blue, Manganese Blue, Chromium Oxide Green, Hydrated Chromium Oxide Green, Cobalt Green, Cerium Sulfide, Cadmium Sulfide, Sulfonated Cadmium Selenide, Zinc Ferrate, Bismuth Vanadate, Prussian Blue, Mixed Metal Oxides, Azo, Azo Methanogen, methine, anthraquinone, phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazinindigo, dioxazine, iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone, indanthrone, anthrapyrimidine and quinophthalone pigments. When present, the inorganic pigments, organic pigments or mixtures thereof described herein are preferably present in a total amount of about 0.1 wt % to about 45 wt %, the weight percentages being based on the total weight of the security ink composition.

[0105] According to one aspect of the present invention, the security ink composition described herein is an optically variable ink and comprises an optically variable pigment or a mixture of different optically variable pigments. The optically variable ink may further comprise one or more color constant pigments. The optically variable ink preferably comprises an optically variable pigment or a mixture of different optically variable pigments. Wherein the optically variable pigment is preferably selected from the group consisting of: thin film interference pigments, interference coating pigments, cholesteric liquid crystal pigments and mixtures thereof. When present, the optically variable pigment described herein is contained in a total amount between about 5 wt % and about 40 wt %, more preferably in a total amount between about 10 wt % and about 35 wt %, the weight percentages being based on the total weight of the security ink composition.

[0106] The security ink described herein may further include one or more machine readable compounds known in the art. Such machine readable compounds or taggants or markers may be included for forensic detection purposes. Various devices such as (FT) IR spectrometers, fluorometers / luminescence detectors, optical microscopes, scanning or tunneling electron microscopes, Raman spectrometers may be used to detect such machine readable compounds.

[0107] Suitable machine-readable IR absorbing compounds are described in WO 2019 / 002046 A1, the disclosure of which is incorporated herein by reference.

[0108] Suitable machine-readable organic luminescent compounds are described in WO 2011 / 147587 A1, WO 2012 / 160182 A1, WO 2013 / 068324 A1, WO 2013 / 068275 A1, WO 2013 / 075980 A1, WO 2013 / 079521 A1, while inorganic luminescent compounds are described in WO 2014 / 048702 A1, WO 2018 / 172318 A1, WO 2009 / 006634 A1, WO 2011 / 002960 A1, WO 2011 / 041657 A1. Said documents are incorporated herein by reference.

[0109] Suitable machine readable SERS compounds are described in US 5609907 A, WO 1998 / 010289 A1, WO 2010 / 135354 A1 and WO 2010 / 135351 A1. Said documents are incorporated herein by reference.

[0110] Suitable machine readable compounds with a specific shape and / or indicia that require magnification to be observed are described in, for example, US2012 / 107 738A1, US2009 / 2017 842A1, US2008 / 236 447A1, US2008 / 107856A1, US2008 / 088 895A1, US 7 639 109 B2, US 7 241489B2, US 7 645 510 B2 and EP 1 741 757 B1. The documents are incorporated herein by reference.

[0111] The security ink described herein may further comprise one or more additives, including but not limited to compounds and materials for adjusting physical, rheological and chemical parameters of the security ink, such as consistency (e.g. anti-settling agents and plasticizers), foaming (e.g. defoamers and degassing agents), lubricity (waxes), UV stability (light stabilizers), adhesion, surface properties (wetting agents, oleophobes and hydrophobes), drying / curing properties (curing accelerators, sensitizers, crosslinkers), etc. The additives described herein may be present in the security ink described herein in amounts and forms known in the art, including in the form of so-called nanomaterials in which at least one dimension of the additive is in the range of 1 to 1000 nm.

[0112] The present invention further provides a method for producing the security ink described herein and the security ink obtained thereby. The security ink described herein can be prepared by: 3 Fe 5- x M x O 12 The pigment and all other ingredients are dispersed or mixed to form a liquid or pasty ink. When the security ink described herein is an oxidative drying gravure ink, one or more oxidative drying agents are usually added at the end of the dispersion process. When the security ink described herein is a UV-VIS curable security ink, one or more photoinitiators may be added to the composition during the dispersion or mixing step of all other ingredients, or one or more photoinitiators may be added to the composition at a later stage, i.e. after the liquid or pasty ink is formed. The varnish, binder compound, monomer, oligomer, resin and additives are generally selected from those known in the art and as described above, and depend on the printing method used to apply the security ink described herein to the substrate described herein.

[0113] The security ink described herein is applied to a substrate described herein by coating, spraying, extrusion or a mixture of these application techniques to produce at least one machine-readable security feature.

[0114] In a preferred embodiment, a printing method is used for security ink application, the printing method is preferably selected from the group consisting of: offset printing method, gravure printing method, screen printing method, rotogravure printing method, flexographic printing method and inkjet printing method, more preferably selected from the group consisting of: gravure printing method, screen printing method, rotogravure printing method, flexographic printing method and flexographic inkjet printing method, still more preferably selected from the group consisting of: gravure printing method, screen printing method and rotogravure printing method.

[0115] The present invention further provides a method for producing at least one machine-readable security feature as described herein. The method comprises the following steps a): applying the security ink as described herein to the substrate as described herein, preferably by a printing method selected from the group consisting of gravure printing, screen printing, flexographic printing, rotogravure printing and inkjet printing.

[0116] After step a), step b) is performed of drying and / or curing the security ink in the presence of UV-VIS radiation and / or air or heat to form at least one machine-readable security feature as described herein on the substrate.

[0117] The invention further provides at least one machine-readable security feature made from a security ink as described herein on a substrate as described herein.

[0118] The substrate described herein is preferably selected from the group consisting of: paper or other fibrous materials such as cellulose (including woven and non-woven fibrous materials), paper-containing materials, glass, metals, ceramics, plastics and polymers, metallized plastics or polymers, composite materials and mixtures or combinations of two or more thereof. Typical paper, paper-like or other fibrous materials are made from various fibers, including, but not limited to, abaca, cotton, flax, wood pulp and blends thereof. As is well known to those skilled in the art, cotton and cotton / flax blends are preferably used for banknotes, while wood pulp is typically used for non-banknote security documents. Typical examples of plastics and polymers include: polyolefins such as polyethylene (PE) and polypropylene (PP) including biaxially oriented polypropylene (BOPP), polyamides, polyesters such as poly(ethylene terephthalate) (PET), poly(1,4-butylene terephthalate) (PBT), poly(ethylene 2,6-naphthoate) (PEN) and polyvinyl chloride (PVC). As shown in the trademark Those spunbond olefin fibers sold under the trade mark can also be used as substrates. Typical examples of metallized plastics or polymers include the above-mentioned plastic or polymer materials on which metals are deposited continuously or discontinuously. Typical examples of metals include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), combinations of alloys thereof and two or more of the above-mentioned metals. The metallization of the above-mentioned plastic or polymer materials can be accomplished by electrodeposition methods, high vacuum coating methods or by sputtering methods. Typical examples of composite materials include, but are not limited to: paper and at least one plastic or polymer material such as those mentioned above and a multilayer structure or laminate of plastic and / or polymer fibers introduced into paper-like or fiber materials such as those mentioned above. Of course, the substrate may further contain additives known to those skilled in the art, such as fillers, sizing agents, brighteners, processing aids, reinforcing or wetting agents, etc.

[0119] The present invention further provides a security document comprising a substrate as described herein and at least one machine-readable security feature as described herein or a security document comprising more than one machine-readable security feature as described herein. Security documents include, but are not limited to, valuable documents and valuable commodities. Typical examples of valuable documents include, but are not limited to, banknotes, contracts, bills, checks, vouchers, stamps and tax labels, and agreements, etc., identity documents such as passports, identity cards, visas, driver's licenses, bank cards, credit cards, transaction cards, pass documents or cards, admission tickets, and public transportation tickets or titles, etc. The term "valuable commodity" refers to packaging materials, especially packaging materials for pharmaceutical, cosmetic, electronic or food industries, which can be protected from counterfeiting and / or illegal copying to ensure the contents of the package, such as genuine drugs. Examples of these packaging materials include, but are not limited to, labels, such as authentication brand labels, tamper-evident labels, and seals. Preferably, the security document described herein is selected from the group consisting of: banknotes, identity documents, authorization documents, driver's licenses, credit cards, access cards, transportation title documents, vouchers and security product labels. Alternatively, the security features described herein can be produced on an auxiliary substrate, such as, for example, a security thread, a security strip, a foil, a decal, a window or a label, and thus transferred to the security document in a separate step. The substrates, valuable documents and valuable goods mentioned are exemplary and do not limit the scope of the present invention.

[0120] For the purpose of further increasing the security level of the security document and the resistance to counterfeiting and illegal reproduction, the substrate described herein may contain printed, coated or laser-marked or laser-perforated markings, watermarks, anti-counterfeiting security threads, fibers, planks, luminescent compounds, windows, foils, labels, primers and combinations of two or more thereof, provided that these potential additional elements do not negatively interfere with the magnetic detectability of the applied, preferably printed, at least one machine-readable security feature.

[0121] One or more protective layers may be applied over at least one machine-readable security feature or security document as described herein for the purpose of increasing durability through stain or chemical resistance and cleanliness and thereby increasing the cycle life of the security document, or for the purpose of changing their aesthetic appearance (e.g. optical gloss). When present, the one or more protective layers are typically made of a protective varnish, which may be transparent or slightly tinted or colored and may be more or less glossy. The protective varnish may be a radiation curable composition, a thermal drying composition or any combination thereof. Preferably, the one or more protective layers are made of a radiation curable composition, more preferably a UV-Vis curable composition.

[0122] The at least one machine-readable security feature described herein may be provided directly on a substrate, where the at least one machine-readable security feature will remain permanently on the substrate (e.g. for banknote applications). Alternatively, the at least one machine-readable security feature may also be provided on a temporary substrate for production purposes, from which the at least one machine-readable security feature is subsequently removed. Thereafter, the temporary substrate may be removed from the at least one machine-readable security feature after the security ink described herein for producing the at least one machine-readable security feature has hardened / cured.

[0123] Alternatively, in another embodiment, an adhesive layer may be present on at least one machine-readable security feature, or may be present on a substrate comprising the machine-readable security feature, the adhesive layer being on a side of the substrate opposite to a side on which the machine-readable security feature is provided, or on a side identical to the machine-readable security feature and on the top of the machine-readable security feature. Therefore, an adhesive layer may be applied to the machine-readable security feature or to the substrate, the adhesive layer being applied after the drying or curing step has been completed. Such articles may be attached to documents or other articles of all kinds without the need for printing or other processes involving machinery and a considerable amount of work. Alternatively, the substrate comprising the machine-readable security feature described herein may be in the form of a transfer foil, which may be applied to a document or article in a separate transfer step. For this purpose, the substrate is provided with a release coating, as described herein, on which a machine-readable security feature is produced. More than one adhesive layer may be applied to the dry machine-readable security feature thus produced.

[0124] Also described herein are substrates, security documents, decorative elements and objects comprising more than one, i.e. two, three, four, etc., at least one machine-readable security feature described herein. Also described herein are articles, in particular security documents, decorative elements or objects, comprising at least one machine-readable security feature described herein.

[0125] As mentioned above, the at least one machine-readable security feature described herein may be used to protect and authenticate a security document or decorative element.

[0126] Typical examples of decorative elements or objects include, but are not limited to, luxury goods, cosmetic packaging, vehicle parts, electronic / electrical appliances, furniture, and nail art items.

[0127] Containing at least one non-luminescent undoped Y 3 Fe 5-x M x O 12 The at least one machine-readable security feature of the pigment may consist of indicia, wherein the indicia refers to codes (such as bar codes or QR codes), symbols, alphanumeric symbols, motifs, geometric patterns, letters, words, numbers, logos, pictures, portraits and combinations thereof.

[0128] According to one embodiment, a substrate, a security document or an article as described herein comprises a combined security feature made of a first region and a second region, the first region being composed of at least one machine-readable security feature as described herein, the at least one machine-readable security feature being derived from a substrate comprising at least one non-luminescent undoped Y-terminal as described herein. 3 Fe5- x M x O 12 The non-luminescent undoped pigment is a pigment-based safety ink, wherein the non-luminescent undoped pigment is absent from the second region. The first and second regions may be adjacent, partially overlap each other or spaced apart. The first and second regions may construct an image and may be made of an ink comprising one or more compounds (e.g. pigments or dyes) absorbing in the visible region of the electromagnetic spectrum, the compounds being selected in such a way that the two regions are preferably color matched in the visible spectrum.

[0129] Another embodiment of the present invention is directed to a method for authenticating a security document or article comprising the steps of:

[0130] a) providing a security document or article comprising at least one machine-readable security feature as described herein;

[0131] b) defining, for the purpose of FMR signal detection, at least one area of ​​the security document or article containing the at least one machine-readable security feature;

[0132] c) detecting and recording an FMR spectrum of at least one machine-readable security feature to provide a recorded FMR spectrum containing sufficient data points to establish at least one FMR characteristic;

[0133] d) parameterizing or directly using the recorded FMR spectra to establish at least one regionally defined FMR characteristic;

[0134] e) comparing the at least one regionally defined FMR characteristic established from step d) with at least one predefined or expected FMR characteristic;

[0135] f) determining the authenticity of the security document or article based on the comparison operation performed under step e).

[0136] A security document or article comprising at least one machine-readable security feature as described herein is subjected to a treatment of at least one non-luminescent undoped Y- 3 Fe 5-x M x O 12 The invention relates to the detection of a ferromagnetic signal characteristic of a pigment. The detection is performed at a predefined area of ​​a security document or article, where a security ink composition has been applied, preferably printed, to form a machine-readable security feature. To determine authenticity, at least one regionally defined FMR characteristic established is compared with an FMR characteristic expected at a defined area of ​​the security document or article but not at another area. Thus, if the established FMR characteristic is not determined at a defined area or is observed at a non-defined area, the sample is classified as inauthentic.

[0137] FMR detection can be performed by systems based on known techniques, such as readily available microwave electronics and permanent magnet arrangements. Specifically, detection can be performed by frequency sweeping of an IQ demodulator-based impedance measurement system with a fixed magnet, a locked oscillator-based detector with a fixed magnet, or a discrete matrix of fixed frequency IQ demodulator-based impedance measurement systems with a fixed magnet. The use of other detection means is entirely within the purview of those skilled in the art. The detected FMR signals can then be recorded and stored using computerized means.

[0138] After detecting and recording an FMR spectrum as described herein, at least one regionally defined FMR feature is derived from the recorded spectrum. As described herein, the spectrum itself or optionally at least one suitable mathematically derived parameterized representation of the spectrum can be obtained. Thus, for authentication purposes, the FMR spectrum results in the generation of at least one regionally defined FMR characteristic in a suitable form.

[0139] For at least one non-luminescent undoped Y 3 Fe 5-x M x O 12 One or more statistically expected "reference" characteristics can be derived from a particular machine-readable security feature produced by a pigment and a blend of said individual pigments, which can be compared to one or more established regionally defined FMR characteristics. Another method involves comparing the established regionally defined FMR characteristics with at least one regionally defined FMR characteristic previously measured and stored for the same pigment or pigment blend. Regardless of the comparison method, at least one regionally defined FMR characteristic produced is checked for consistency or compared to at least one expected FMR characteristic. Such a comparison does not need to result in a perfect match, but only needs to meet an acceptable or minimum tolerated industry-defined threshold or confidence limit to classify at least one machine-readable security feature as true (i.e., authentic) or not authentic. In other words, if the threshold is met, the security document or article is classified as authentic.

[0140] Without departing from the spirit of the present invention, those skilled in the art may conceive of several modifications to the above specific embodiments. These modifications are included in the present invention.

[0141] Example

[0142] The invention will now be described in more detail with reference to non-limiting examples.The following Examples E1-E16 and Comparative Examples C1-C8 provide details on the preparation of the security inks described herein, and the magnetic and optical properties of the machine-readable security features obtained therefrom.

[0143] A. Magnetic properties of machine-readable security features

[0144] A-1. Ferromagnetic resonance (FMR) characteristics

[0145] The ferromagnetic resonance of the machine-readable security features obtained from the security inks E1-E16 of the invention and the comparative inks C1-C8 was evaluated using a PhaseFMR-40 apparatus (Nanosc Instruments AB, Kista, Sweden) equipped with a 5403 magnet from GMW Associates (San Carlos USA). The PhaseFMR-40 was operated in CPW mode (coplanar waveguide) with a 5 mm x 5 mm sample of the security features placed inverted thereon. To obtain the FMR spectrum of the measured sample, the RF frequency was fixed at 5 GHz while the magnetic field was scanned between 0 and 2500 Oe in steps of 10 Oe. The resulting FMR spectra were displayed as the first derivative of the resonance signal using a locked field modulation with a peak-to-peak amplitude of 20 Oe and a frequency of 490 Hz.

[0146] From the FMR spectrum, two parameters are obtained:

[0147] - Line center field (@5GHz): This is the field where the FMR spectrum of the security feature passes through 0 (ie the field at maximum amplitude of the resonant signal).

[0148] - Linewidth: This is the line width at half height or half prominence of the resonant signal.

[0149] The line center field and line width in Oe measured at an RF frequency of 5 GHz for the security features obtained from the inventive security inks E1-E16 and comparative inks C1-C8 are reported in Table 7 below.

[0150] At a given RF frequency, the line center field and line width depend only on the molar concentration of element M in the YI(M)G pigment (i.e., the number of iron atoms in the unit cell that have been replaced by element M), and are independent of the type of ink shown in Table 7.

[0151] A-2. Comprehensive magnetic susceptibility

[0152] The integrated magnetic susceptibility of the machine-readable security features obtained from the security inks E1-E16 of the invention and the comparative inks C1-C8 was evaluated using a QCD200Mag apparatus from Giesecke & Devrient GmbH (München, Germany). The measurements were performed on dried and / or cured homogenized samples of the security inks E1-E16 of the invention and the comparative inks C1-C8 according to the Giesecke & Devrient guidelines (QCD 200MAG operating manual Art. No 221312001).

[0153] The combined magnetic susceptibility of the machine-readable security features obtained from the inventive security inks E1-E16 and comparative inks C1-C8 is reported in Table 7 below.

[0154] B. Optical properties of machine-readable security features

[0155] B-1.L* value

[0156] The L* values ​​of the machine-readable security features obtained from the inventive security inks E8-E16 and the comparative inks C4-C8 (screen printing inks) were obtained independently from measurements of printed machine-readable security features according to CIELAB (1976), a* and b* being color coordinates in a Cartesian two-dimensional space (a*=color value along the red / green axis, b*=color value along the blue / yellow axis). The L*a*b* values ​​were measured independently with a spectrophotometer DC 45IR from Datacolor (measurement geometry: 45 / 0°; spectrum analyzer: proprietary dual-channel holographic grating. 256 photodiode linear array was used for both reference and sample channels; light source: full bandwidth LED illumination). The L* values ​​of the security features obtained from the inventive inks E8-E16 and the comparative inks C4-C8 are reported in Table 8 below.

[0157] B-2.IR reflection spectrum

[0158] The reflectance spectra of machine-readable security features made from the inventive security inks E8-E16 and comparative inks C4-C8 were measured independently between 400 nm and 1100 nm with a DC45IR from Datacolor. The internal standard of the device was used to measure the 100% reflectance. The reflectance values ​​(in %) of the security features obtained from the inventive security inks E8-E16 and comparative inks C4-C8 at selected wavelengths in the NIR range (700-1100 nm) are reported in Table 8 below.

[0159] C. Y 3 Fe 5-x M x O 12 Pigments

[0160] The particle size d of pigments P1 and P2-P7 was measured by laser diffraction measurement (Beckmann Laser LS). 50 The general formula of pigments P1-P7 is Y 3 Fe 5-x Al x O 12 , the value of x varies between 0 and 1.5, corresponding to an Al / Fe ratio between 0 and 30 mol%. Stoichiometry and particle size d of pigments P1-P7 50 This is given in Table 1 below:

[0161] Table 1. Pigments P1-P7 and their characteristics

[0162] Pigment P Chemical formula Al / Fe ratio Fe replaced by Al [mol%] <![CDATA[Particle size d 50 [μm]]]> P1 <![CDATA[Y 3 Fe 5 O 12 ]]> 0 0 9.9 P2 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 4.99 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.01 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.002 0.2 7.4 P3 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 4.975 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.025 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.005 0.5 7.2 P4 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 4.9 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.1 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.02 2 8.0 P5 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 4.75 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 0.25 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.053 5 8.0 P6 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 4 <h2 style=";text-align:left;direction:ltr"> AlO<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.25 20 5.8 P7 <h2 style=";text-align:left;direction:ltr"><![CDATA[Y <h2 style=";text-align:left;direction:ltr"> 3 <h2 style=";text-align:left;direction:ltr"> Fe<h2 style=";text-align:left;direction:ltr"> 3.5 <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> 1.5 <h2 style=";text-align:left;direction:ltr"> O<h2 style=";text-align:left;direction:ltr"> 12 <h2 style=";text-align:left;direction:ltr"> ]]><h2 style=";text-align:left;direction:ltr"> 0.43 30 5.8

[0163] D. Preparation of the safety inks E1-E15 of the present invention and comparative inks C1-C8

[0164] D-1. Oxidative Drying Gravure Inks E1-E6 and Comparative Inks C1-C2

[0165] To prepare the inventive security inks E1-E6 and comparative inks C1-C2, the ingredients listed in Table 2 were mixed thoroughly by hand with a spatula until they were visually homogeneous. The resulting pasty ink was ground on a three-roll mill (Bühler 200SDV) at 25° C. in 2 separate passes (the first at 6 bar and the second at 12 bar).

[0166] The flow rate was measured on a Haake Roto Visco 1 rotational rheometer (40 °C and 1000 s -1 The viscosity of the gravure magnetic oxidative drying ink thus obtained was measured on a cone plate with a 20 mm, 0.5° geometry, cut off at 25 μm).

[0167] Table 2. Compositions of oxidatively drying gravure inks E1-E6 and C1-C2

[0168]

[0169] D-2. UV curing gravure ink E7 and comparative ink C3

[0170] To prepare the inventive security ink E7 and the comparative ink C3, the ingredients listed in Table 3 were mixed separately at room temperature for 3 minutes using a DAC 150SPCM 31 high-speed mixer (Hauschild) at 2500 rpm. The resulting paste was ground separately three times on a three-roll mill (Bühler 200SDV) at 25° C. (the first time at a pressure of 8 bar, the second and third times at a pressure of 11 bar).

[0171] The viscosity of the ink was determined as described above in Item D-1.

[0172] Table 3. Composition of UV curable gravure inks E7 and C3

[0173]

[0174] D-3. UV-curable hybrid (cationic / radical) screen printing inks E8-E14 and comparative inks C4-C6

[0175] To prepare the security inks E8-E14 of the present invention and the comparative inks C4-C6, the components of the ink carrier provided in Table 4 (i.e., all components of the ink except the iridescent pigment and the pigments P1-P7) were mixed and dispersed at room temperature using a Dispermat (model CV-3) at 2000 rpm for 10 minutes. Pigments P1-P7 (except C4) were then added separately and further dispersed at 2500 rpm for 3 minutes at room temperature. Finally, the iridescent pigment was added and dispersed at 2500 rpm for 3 minutes at room temperature.

[0176] The viscosity values ​​provided in Table 4 were independently measured at 25° C. using a Brookfield viscometer (model “DV-IPrime”, spindle S27 at 100 rpm).

[0177] Table 4. Compositions of Screen Printing Inks E8-E14 and Comparative Inks C4-C6

[0178]

[0179] D-4. UV curable free radical screen printing ink E15 and comparative ink C7

[0180] To prepare the inventive security ink E15 and comparative ink C7, the components of the ink vehicle provided in Table 5 (i.e., all components of the ink except the iridescent pigment and YIG pigment P6) were mixed and dispersed at room temperature using a Dispermat (model CV-3) at 2000 rpm for 10 minutes. Pigment P6 (except C7) was then added and further dispersed at 2500 rpm for 3 minutes at room temperature. Finally, the iridescent pigment was added and dispersed at 2500 rpm for 3 minutes at room temperature.

[0181] The viscosity of the ink was determined as described above in Item D-3.

[0182] Table 5. Composition of screen printing inks E15 and C7

[0183]

[0184] D-5. Thermal drying solvent screen printing ink E16 and comparative ink C8

[0185] The components of the ink vehicle described in Table 6 (i.e., all components of the ink except the iridescent pigment and the YIG pigment) were mixed and dispersed at room temperature using a Dispermat (Model CV-3) at 2000 rpm for 10 minutes. Pigment P6 (except C8) was then added and dispersed at 2500 rpm for 3 minutes. Finally, the iridescent pigment was added and dispersed at 2500 rpm for 3 minutes to obtain the solvent screen printing security inks C8 and E15 described in Table 6.

[0186] The viscosity values ​​provided in Table 6 were independently measured at 25° C. using a Brookfield viscometer (model “DV-IPrime”, spindle S27 at 50 rpm).

[0187] Table 6. Composition of screen printing inks E16 and C8

[0188]

[0189] E. Preparation of machine-readable security features obtained from the security inks E1-E16 of the invention and the comparative inks C1-C8

[0190] E-1. Machine-readable security features from oxidatively drying intaglio inks E1-E6 and comparative inks C1-C2

[0191] Oxidative drying intaglio inks E1-E6 and C1-C2 were independently printed with an Ormag intaglio proofer using an intaglio printing plate consisting of a set of engravings of different depths (about 20 μm to about 100 μm) and widths (about 60 μm to about 500 μm) in a "U" shape, such as to simulate the "guilloche" pattern on banknotes. The intaglio printing plate was heated at 60° C. and the oxidative drying intaglio inks E1-E6 and C1-C2 were independently applied to fiduciary paper (BNP paper from Louisenthal, 100 g / m 2 , 20cm×4cm), and the excess ink was manually wiped off with paper. The size of the guilloche pattern is 5.4cm×2.5cm.

[0192] The resulting security feature was dried in the dark for 7 days. 3 samples of each security ink were printed and the samples were subjected to the tests described above under items A-1 and A-2.

[0193] E-2. Machine readable security features from UV curable intaglio ink E7 and comparative ink C3

[0194] UV curable gravure inks E7 and C3 were printed independently as described under item E-1. The printed security features were dried using a Technigraf AKTIPRINT 18-2 mercury UV dryer (belt speed 10 m / min, corresponding to approximately 200 mJ / cm 2 Three samples of each security ink were printed and subjected to the tests described above under items A-1 and A-2.

[0195] E-3. Machine Readable Security Features from UV Curable Hybrid (Cationic / Free Radical) and Free Radical Screen Printing Inks E8-E15 and Comparative Inks C4-C7

[0196] UV curing screen printing inks E8-E15 and C4-C7 were individually applied manually to a piece of trust paper (BNP paper from Louisenthal, 100 g / m 2 , 12 cm×4.5 cm) to form a machine-readable security feature in the form of a cured coating with a thickness of about 20 μm. The size of the printed pattern is 3.5 cm×3.5 cm.

[0197] After the printing step, the solidification was carried out in a curing unit from IST Metz GmbH (2 lamps: iron-doped mercury lamp 200 W / cm 2 + Mercury lamp 200W / cm 2 Each security feature was cured by exposing the feature to UV-Vis light twice at a speed of 100 m / min. 3 samples of each security ink were printed and the samples were subjected to the tests described above under item A-1-B-2.

[0198] E-4. Machine Readable Security Features from Thermal Drying Solvent Screen Printing Ink E16 and Comparative Ink C8

[0199] Heat drying solvent screen printing inks E16 and C8 were individually applied manually to a piece of trust paper (BNP paper from Louisenthal, 100 g / m 2 , 12 cm x 4.5 cm) to form a machine-readable security feature in the form of a dry coating with a thickness of about 6-9 μm. The size of the printed pattern is 3.5 cm x 3.5 cm.

[0200] After the printing step, each security feature was dried for about 1 minute using a hot air dryer at a temperature of about 50° C. Three samples of each security ink were printed and subjected to the tests described above under item A-1-B-2.

[0201] F. Results from machine-readable security features of security inks E1-E16 of the invention and comparative inks C1-C8) F-1. FMR characteristics (line width and line center field) and comprehensive magnetic susceptibility

[0202] Table 7 shows the FMR characteristic performance (line width and line center field) and integrated magnetic susceptibility of machine-readable security features obtained by printing and drying and / or curing the security inks E1-E16 of the present invention and the comparative inks C1-C8. The tests were performed according to the procedures described under items A-1 and A-2.

[0203] Table 7

[0204]

[0205]

[0206] F-2. Optical properties (L*a*b* values ​​and NIR reflection)

[0207] Table 8 shows the optical properties of machine-readable security features obtained by printing and drying and / or curing the inventive screen-printing security inks E8-E16 and comparative inks C4-C8. The tests were performed according to the procedures described under items B-1 and B-2.

[0208] Table 8

[0209]

Claims

1. A security ink composition comprising at least one non-luminescent undoped Y3Fe 5-x M x O 12 Pigments, Where x satisfies the condition 0≤x≤1.25; M is selected from the group consisting of: aluminum, gallium or calcium and mixtures thereof; and wherein after drying and / or curing, at least one machine-readable security feature derived from the application, preferably printing, of the security ink composition has a thickness of at least about 200×10 -12 m 3 The integrated magnetic susceptibility of the material is measured and exhibits ferromagnetic resonance (FMR) characteristics for authentication purposes. 2 . The security ink composition according to claim 1 , wherein x satisfies the condition 0.10≤x≤1.

25.

3. The security ink composition according to claim 1 or 2, wherein x satisfies the condition 0.25≤x≤1.

00.

4. The security ink composition according to claims 1 to 3, wherein M is aluminum.

5. The security ink composition according to claims 1 to 4, wherein the pigment is present in at most 40 wt.%, preferably at most 20 wt.% of the security ink composition.

6. The security ink composition according to claims 1 to 5, comprising at least one additional non-luminescent undoped Y3Fe 5-x M x O 12 A pigment, wherein x satisfies the condition 0≤x≤5, preferably 0≤x≤4.99; M is selected from the group consisting of aluminum, gallium or calcium or mixtures thereof; And wherein upon drying and / or curing, the applied, preferably printed, at least one machine-readable security feature derived from the security ink composition exhibits ferromagnetic resonance (FMR) properties for authentication purposes.

7. The security ink composition according to claims 1 to 6, further comprising at least one machine readable compound selected from the group consisting of: a luminescent pigment, an IR absorbing pigment or a SERS compound.

8. The security ink composition according to any one of the preceding claims, wherein the security ink composition is a gravure ink composition having a viscosity in the range of about 3 to 60 Pa·s at 40°C.

9. The security ink composition according to claims 1 to 7, wherein the security ink composition is a screen printing ink composition having a viscosity in the range of about 0.05 to 5 Pa·s at 25°C.

10. A machine-readable security feature comprising at least one security ink composition according to any one of the preceding claims.

11. A security document or article comprising at least one machine-readable security feature according to claim 10.

12. A security document or article as claimed in claim 11, comprising at least one further additional and different security feature.

13. A method for authenticating a security document or article, comprising the steps of: a) providing a security document or article according to claim 11, said security document or article comprising at least one machine-readable security feature according to claim 10; b) defining, for the purpose of FMR signal detection, at least one area of ​​the security document or article containing the at least one machine-readable security feature; c) detecting and recording an FMR spectrum of the at least one machine-readable security feature to provide a recorded FMR spectrum containing sufficient data points to establish at least one FMR characteristic; d) parameterizing or directly using said recorded FMR spectra to establish at least one regionally defined FMR characteristic; e) comparing the at least one regionally defined FMR characteristic established from step d) with at least one predefined or expected FMR characteristic; f) determining the authenticity of the security document or article based on the comparison operation performed under step e).

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