Security ink and machine-readable security features

Abstract

The present invention relates to security inks, security documents or articles suitable for printing machine-readable security functions onto a substrate, as well as machine-readable security functions produced from the security ink, and security documents having machine-readable security functions produced from the security ink. In particular, the present invention provides a security ink comprising one or more IR-absorbing materials that enables the generation of machine-readable security functions.

Description

Detailed description of the invention

[0001]

[0001] The present invention relates to the field of aqueous security inks suitable for printing machine-readable security functions on a substrate, particularly on security documents or articles.

[0002] [Background of the Invention]

[0002] The quality of color photocopying and printing is constantly improving, and it has become common practice to incorporate various security features into security documents such as banknotes, valuable documents or cards, transport tickets or cards, tax banderols and product labels, in an attempt to protect these documents from counterfeiting, alteration, or illegal copying.

[0003]

[0003] For example, security features for security documents can be classified into "overt" and "covert" security features. Overt security features are easily detectable by the senses of an unassisted human, and such features may be visible and / or detectable via touch, for example, while still difficult to produce and / or replicate, whereas covert security features typically require specialized equipment and knowledge to detect them.

[0004]

[0004] For example, machine-readable inks such as magnetic inks, luminescent inks and infrared (IR) absorbing inks are widely used in the field of security documents, particularly for banknote printing, to generate potential security features. In the field of security and protection of valuable documents and goods against counterfeiting, alteration and illegal reproduction, it is known in the art that machine-readable security inks can be applied by various printing processes, including printing processes using highly viscous or paste-like inks such as offset printing, letterpress printing and intaglio printing (also referred to in the art as engraved steel die or copper plate printing), and printing processes using liquid inks such as gravure printing, flexographic printing, screen printing and inkjet printing.

[0005]

[0005] Security features including infrared (IR) absorbing materials are widely known and used in security applications. IR absorbing materials commonly used in the field of security are based on the absorption of electromagnetic radiation due to electronic transitions in the spectral range between 780 nm and 1400 nm (the range defined by the CIE (Commission Internationale de l'Eclairage)), this portion of the electromagnetic spectrum is commonly referred to as the NIR region. For example, IR absorbing features are implemented in banknotes used by automated currency processing machines in banking and sales applications (such as ATMs and vending machines) to recognize the determined currency and verify its authenticity, particularly to distinguish it from copies made by color photocopiers. IR absorbing materials include organic compounds, inorganic materials, and glass containing substantial amounts of IR absorbing atoms, ions, or molecules. Typical examples of IR-absorbing compounds include, among others, carbon black, quinone-diinmonium or ammonium salts, polymethines (e.g., cyanine, squaline, croconine), phthalocyanine or naphthalocyanine types (IR-absorbing π-type), dithiolene, quarterylenediimide, metal salts, metal oxides, and metal nitrides.

[0006]

[0006] Due to its strong absorption in the visible region, carbon black is not a preferred security material, as this strong absorption limits the freedom to design security documents that are protected from forgery or illegal copying.

[0007]

[0007] Ideally, security features including infrared (IR) absorbing materials for authentication purposes should not absorb in the visible range (400 nm to 700 nm) in order to enable their use in, for example, all types of visible colored inks and in marks that are invisible to the naked eye or partially visible, and at the same time exhibit strong absorption in the infrared or near-infrared range in order to enable their easy recognition by, for example, standard currency processing equipment.

[0008]

[0008] Organic NIR absorbers are typically limited in use in security applications due to their inherently low thermal stability, low lightfastness, and the complexity of their manufacture.

[0009]

[0009] Improved inorganic IR-absorbing compounds are disclosed in International Publication No. 2007 / 060133A2 and International Publication No. 2020 / 239740A1. International Publication No. 2007 / 060133A2 discloses intaglio printing inks, and International Publication No. 2020 / 239740A1 discloses liquid inks, which include IR-absorbing materials comprising transition element compounds in which IR absorption is the result of electron transitions in the d-shell of atoms or ions of transition elements. However, several concerns have been raised regarding solvent-based inks, and due to environmental toxicity and flammability issues arising from the use of volatile organic solvents, there is a growing momentum to replace or supplement solvent-based inks with aqueous counterparts.

[0010]

[0010] UV-curable inks can be considered expensive and require complex equipment. Furthermore, the high ratio required between binder and pigment makes it difficult to prepare a matte printing function. Water-based inks containing polyurethane resin have the problem of reduced stability during storage due to increased viscosity, and water-based inks containing acrylic resin and IR absorbing materials, as described in International Publication No. 2020 / 239740A1 and International Publication No. 2007 / 060133A2, have the problem of poor optical properties in terms of yellowing during aging.

[0011]

[0011] Therefore, there is still a need for an aqueous security ink comprising one or more IR-absorbing materials for printing machine-readable security functions that has advantages over the prior art and exhibits good physicochemical properties while maintaining good optical properties in the visible and near-IR ranges with respect to use and time.

[0012] [overview]

[0012] Therefore, an object of the present invention is to overcome the defects of the prior art as described above.

[0013]

[0013] In a first aspect, the present invention relates to a security ink for printing machine-readable security functions, having a viscosity between 100 and 3000 mPa s at 25°C and a pH between about 7.0 and about 9.0. a) Water in an amount of at least about 45% by weight, preferably about 45% to about 75% by weight, b) A binder containing one or more types of acrylic resins, present in an amount of approximately 10% to approximately 40% by weight. c) One or more IR absorbing materials in a total amount of approximately 5% to 25% by weight, preferably approximately 7% to 15% by weight, consisting of copper (Cu) and phosphate (PO4 3- ), hydrogenophosphate (HPO4 2- ), pyrophosphate (P2O7 4- ), metaphosphate (P3O9 3- ), fluoride, chloride, sulfate (SO4 2-) and hydroxide (OH - ) selected from the group consisting of; preferably phosphate (PO4 3- ), hydrogenophosphate (HPO4 2- ), pyrophosphate (P2O7 4- ), metaphosphate (P3O9 3- ), polyphosphate and hydroxide (OH - ) selected from the group consisting of; more preferably phosphate (PO4 3- ) and hydroxide (OH - ) selected from the group consisting of one or more anions, one or more IR absorbing materials, d) one or more zinc aluminum phosphate compounds in an amount of about 0.125 wt% to about 5.0 wt%, and the ratio (R) between the amount of the one or more zinc aluminum phosphate compounds and the total amount of the one or more zinc aluminum phosphate compounds and the one or more IR absorbing materials is between about 2.0 and about 20, one or more zinc aluminum phosphate compounds, e) optionally, one or more additives selected from fillers, waxes, surfactants, defoamers, thickeners and mixtures thereof to provide a security ink, wherein the weight percentages are based on the total weight of the security ink.

[0014]

[0014] The use of the security ink described herein for printing a machine-readable security function is also described and claimed herein.

[0015]

[0015] A machine-readable security function made from the security ink described herein is also described and claimed herein.

[0016]

[0016] A method for generating a machine-readable security function described herein, comprising the step of applying the security ink described herein to a substrate by a screen printing process, is also described and claimed herein.

[0017]

[0017] Security documents having machine-readable security features as described herein are also described and claimed herein.

[0018]

[0018] A method for authenticating a security document as described herein, a) A step of preparing a security document described herein, which is made with the ink described herein and has machine-readable security features, b) A step of illuminating a machine-readable security feature with at least one wavelength, or illuminating a machine-readable security feature with at least two wavelengths, wherein one of the at least two wavelengths is in the visible range and the other of the at least two wavelengths is in the IR range. c) A step of detecting the optical properties of a machine-readable security function by detecting light reflected or transmitted by the machine-readable security function at at least one wavelength, or by detecting light reflected or transmitted by the machine-readable security function at at least two wavelengths, wherein one of the at least two wavelengths is in the visible range and the other of the at least two wavelengths is in the IR range. d) A step of determining the authenticity of a security document from the detected optical characteristics of a machine-readable security function. Methods including the above are also described and claimed herein.

[0019]

[0019] The aqueous security inks described herein advantageously enable the production of machine-readable security features that exhibit improved performance in terms of visible optical properties, including reduced yellowing and / or greening during aging, while maintaining good optical properties in the near-IR or IR range with respect to use and time. In addition to the environmentally friendly nature of the aqueous security inks described herein (inks that do not contain volatile organic compounds or contain them in very limited amounts), the improved optical properties of the security features obtained from the aqueous security inks described herein enable their incorporation into and / or on security documents, particularly banknotes, and provide freedom in terms of designing subsequent security printing steps, as described later herein. Advantageously, the aqueous security inks described herein can be used in paper mills where all inks are prepared from aqueous compositions. [Brief explanation of the drawing]

[0020] [Figure 1] This is a photograph of a machine-readable security function comprising an IR-absorbing layer made of the dry security ink according to the present invention and having the shape of two circular geometric patterns, and an IR-transmitting layer made of intaglio ink that partially covers the IR-absorbing layer (Figure 1 left: taken using a phone camera under visible artificial light; and Figure 1 right: taken using a near-IR camera under near-IR light).

[0021] [Detailed explanation]

[0020] The following definitions are used to interpret the meaning of terms discussed in this description and enumerated in the claims.

[0022]

[0021] As used herein, the article "a" indicates one or more than one, and does not necessarily limit the noun it refers to to a singular noun.

[0023]

[0022] As used herein, the term “about” means that the quantity or value may be the specified value or some other value that is approximately the same. The phrase is intended to convey that similar values ​​within ±5% of the indicated value will promote equivalent results or effects according to the present invention.

[0024]

[0023] As used herein, the terms "and / or" or "or / and" mean that any one or all of the elements of the group may be present. For example, "A and / or B" means "A only, or B only, or both A and B."

[0025]

[0024] As used herein, the term “at least” is intended to define one or more than one, for example, one, two or three.

[0026]

[0025] The term “security document” refers to a document that is typically protected from forgery or fraud by at least one security feature. Examples of security documents include, but are not limited to, documents of value and goods of value.

[0027]

[0026] The terms "yellowing" and "greening" refer to the tendency for some inks or coatings to turn yellowish and greenish, and thus change color, during drying and / or aging. Yellowing and greening behavior is defined in the CIE (1976) a * (Green discoloration) and b * Characterized by the color change during drying, curing, and / or aging, as indicated by the (yellowing) parameter, a * This is a horizontal coordinate whose value is in the range of -80 (green) to +80 (red), and b *This is a horizontal coordinate whose value ranges from -80 (blue) to +80 (yellow). Further details regarding the CIE (1976) system can be found in Physics, Chemistry and Technology Vol.3, No.2, 2005, pp. 205-216. In particular, the yellowing and greening behavior of inks or coatings is observed under normal conditions (e.g., laboratory conditions) or under thermal aging (e.g., in an oven at 40°C) over time. * and b * It can be characterized by changes in [something].

[0028]

[0027] The present invention provides a security ink comprising one or more IR-absorbing materials described herein for printing machine-readable security features. As used herein, the term “machine-readable security feature” means an element that exhibits at least one characteristic property detectable by a device or machine, which may be contained in a layer, and which consequently provides a method for authenticating the layer or an article comprising the layer by the use of a specific device for authentication thereof. The machine readability of the security features described herein is embodied by one or more IR-absorbing materials described herein, which are contained in the security ink described herein.

[0029]

[0028] The security inks described herein have a viscosity between approximately 100 mPa s and approximately 3000 mPa s at 25°C, and the viscosity is measured using a Brookfield viscometer ("RVDV-I Prime" model), with the spindle and rotation speed (rpm) being adapted to the following viscosity ranges: for viscosity values ​​between 100 and 500 mPa s, spindle 21 at 100 rpm; for viscosity values ​​between 500 mPa s and 2000 mPa s, spindle 27 at 100 rpm; and for viscosity values ​​between 2000 mPa s and 3000 mPa s, spindle 27 at 50 rpm.

[0030]

[0029] In order to ensure good stability of the ink during storage and, in particular, to avoid aggregation and viscosity increase during storage, the security ink described herein has a pH between about 7.0 and about 9.0, preferably between about 7.5 and 9.0.

[0031]

[0030] One or more IR absorbing materials described herein are present in the security ink described herein in an amount of about 5% to about 25% by weight, more preferably about 7% to about 15% by weight, where the weight percentage is based on the total weight of the security ink. One or more IR absorbing materials described herein are suitable for generating machine-readable security features. One or more IR absorbing materials described herein are copper (Cu) and phosphate (PO4 3- ), hydrogenophosphate (HPO4 2- ), pyrophosphate (P2O7 4- ), metaphosphate (P3O9 3- ), fluoride, chloride, sulfate (SO4 2- ) and hydroxyl (OH - Selected from the group consisting of ); preferably, phosphate (PO4 3- ), hydrogenophosphate (HPO4 2- ), pyrophosphate (P2O7 4- ), metaphosphate (P3O9 3- ), polyphosphates and hydroxides (OH - A phosphate (PO4) is selected from the group consisting of ) 3- ) and hydroxyl (OH -It includes one or more anions selected from the group consisting of ). Examples, though not limited to them, include copper(II) fluoride (CuF2), copper hydroxyfluoride (CuFOH), copper hydroxide (Cu(OH)2), copper hydrate (Cu3(PO4)2·2H2O), anhydrous copper phosphate (Cu3(PO4)2), basic copper(II) phosphate (e.g., Cu2PO4(OH), Cu3(PO4)(OH)3, "cornetite", Cu5(PO4)3(OH)4, "pseudomalachite", CuAl6(PO4)4(OH)8·5H2O, "turquoise", etc.), copper(II) pyrophosphate (Cu2(P2O7)·3H2O), anhydrous copper(II) pyrophosphate (Cu2(P2O7)), and copper(II) metaphosphate (Cu(PO3)2, more precisely denoted as Cu3(P3O9)2). In preferred embodiments, at least one of the one or more IR absorbing materials described herein is Cu2PO4(OH) (CAS No: 12158-74-6), preferably Cu2PO4(OH) having a rivesenite crystal structure.

[0032]

[0031] The one or more IR-absorbing materials described herein preferably have a specific particle size. Herein, the term “size” refers to the statistical properties of the IR-absorbing materials described herein. As is known in the Art, each of the one or more IR-absorbing materials can be independently characterized by measuring the particle size distribution (PSD) of a sample. Such a PSD typically describes the quantity of particles in the sample (with respect to total number, total weight, or total volume) as a function of the size-related properties of the individual particles. A commonly used size-related property describing individual particles is the “circular equivalent” (CE) diameter, which corresponds to the diameter of a circle having the same area as the orthographic projection of the material. In this application, the following values ​​are reported: d(v,50) (hereinafter abbreviated as d50) is the value of the CE diameter in microns that separates the PSD into two equal parts of cumulative volume: the lower part represents 50% of the cumulative volume of all particles, corresponding to particles with a CE diameter smaller than d50; and the upper part represents 50% of the cumulative volume of particles, corresponding to particles with a CE diameter larger than d50. D50 is also known as the median of the particle volume distribution. d(v,98) (hereinafter abbreviated as d98) is the value of the CE diameter in microns that separates the PSD into two parts with different cumulative volumes. As a result, the lower part represents 98% of the cumulative volume of all particles, corresponding to particles with a CE diameter smaller than d98, and the upper part represents 2% of the cumulative volume of particles with a CE diameter larger than d98.

[0033]

[0032] Each of the one or more IR absorbing materials described herein preferably has a median particle size (d50 value) of about 0.01 μm to about 50 μm, more preferably about 0.1 μm to about 20 μm, and even more preferably about 1 μm to about 10 μm, and / or has a particle size (d98 value) of about 0.1 μm to about 100 μm, more preferably about 1 μm to about 50 μm, and even more preferably about 5 μm to about 40 μm. A variety of experimental methods are available to measure PSD, but are not limited to sieving analysis, electrical conductivity measurement (using a Coulter counter), laser diffraction (e.g., Malvern Mastersizer), acoustic spectroscopy (e.g., Quantachrome DT-100), fractional sedimentation analysis (e.g., CPS device), and direct optical particle size distribution. The d50 and d98 values ​​presented herein were measured by laser diffraction under the following conditions: Apparatus: (Cilas 1090); Sample preparation: IR-absorbing material was added to distilled water until the laser obscuration reached an operating level of 13-15%, and the measurement was performed according to ISO standard 13320.

[0034]

[0033] The security inks described herein are aqueous heat-drying inks and are particularly suitable for application to substrates such as those described herein by a printing process preferably selected from the group consisting of gravure printing, flexographic printing, and screen printing, more preferably by screen printing. The heat-drying security inks consist of security inks that are dried by hot air, infrared radiation, or a combination thereof. The heat-drying security inks typically consist of about 20% to about 60% by weight, preferably about 25% to about 55% by weight, solids remaining on the printed substrate, the remainder being one or more water / solvents that evaporate as a result of drying.

[0035]

[0034] Security inks for screen printing are known in the art as requiring low viscosity. Typically, security inks suitable for screen printing processes have a viscosity in the range of about 100 mPa₂s to about 3000 mPa₂s at 25°C, preferably in the range of about 200 mPa₂s to about 2500 mPa₂s, and more preferably in the range of about 200 mPa₂s to about 2000 mPa₂s (e.g., using a Brookfield test machine "RVDV-I Prime", spindle 21 at 100 rpm, spindle 27 at 100 rpm, or spindle 27 at 50 rpm).

[0036]

[0035] The heat-drying screen printing security inks enable the preparation of machine-readable security features (i.e., a dried security ink layer) as described herein, typically having a value between about 3 μm and about 10 μm.

[0037]

[0036] The security inks described herein contain at least about 45% by weight of water, preferably about 45% to about 75% by weight, where the weight percentage is based on the total weight of the security ink.

[0038]

[0037] The security inks described herein contain about 10% to about 40% by weight, preferably about 15% to about 30% by weight, of a binder comprising one or more acrylic resins, the weight percentage being based on the total weight of the security ink.

[0039]

[0038] Preferably, the binder described herein is preferably in the form of an aqueous composition comprising one or more acrylic resins described herein and an optional additional resin described herein, particularly an aqueous emulsion comprising one or more acrylic resins described herein and an optional additional resin described herein, or an aqueous dispersion comprising one or more acrylic resins described herein and an optional additional resin described herein. When one or more acrylic resins are to be used as an aqueous composition, particularly an aqueous emulsion or aqueous dispersion, the amount of the resin presented herein is in the form of solids content / dry content of the resin.

[0040]

[0039] One or more acrylic resins may be homopolymers (i.e., polymers resulting from the polymerization of acrylic acid or methacrylic acid) or copolymers, preferably one or more acrylic resins are copolymers. An acrylic copolymer refers to a polymer resulting from the copolymerization of acrylic acid and / or methacrylic acid with one or more additional monomers or prepolymers.

[0041]

[0040] Preferred monomers include, for example, alkyl (meth)acrylates such as methyl acrylate, propyl acrylate and the like, aryl (meth)acrylates such as phenyl acrylate, benzyl acrylate and the like, styrene and substituted styrenes, vinyl ethers such as methyl vinyl ether, hexyl vinyl ether, benzyl vinyl ether and the like, vinyl halides such as vinyl chloride and vinylidene chloride, vinyl ketones such as methyl vinyl ketone, vinyl carboxylates such as vinyl acetate and vinyl benzoate, unsaturated olefins such as ethylene, propylene or butylene, allyl compounds such as allyl acetate and allyl benzoate, (meth)acrylamides such as N-methyl methacrylamide and N-phenyl methacrylamide, and unsaturated nitriles such as acrylonitrile and methacrylonitrile. Particularly preferred monomers include alkyl (meth)acrylates, vinyl chloride, vinyl acetate and styrene.

[0042]

[0041] Preferred prepolymers, i.e., low molecular weight polymers obtained by another polymerization reaction, include, but are not limited to, polyesters, polyethers, polyamides, polycarbonates, and polyurethanes. Aromatic and aliphatic polyurethanes are particularly preferred.

[0043]

[0042] One or more acrylic resins can be obtained by random copolymerization (i.e., dispersing monomers in an aqueous emulsion and copolymerizing them in the presence of an initiator), or preferably, one or more acrylic resins can be produced as structural copolymers, in which case one or more monomers and / or prepolymers are added in subsequent polymerization steps. Typically, structural copolymers are defined as either block copolymers where the AB or ABA configuration is important and A and B represent a homogeneous arrangement of the same monomer or prepolymer, or graft copolymers where the arrangement of one monomer or prepolymer is distributed along the linear arrangement of other monomers or prepolymers.

[0044]

[0043] Preferably, one or more acrylic resins are water-dispersible, that is, one or more acrylic resins are acrylic resins T g Depending on the value, the material is dispersed in the aqueous phase as a stable emulsion (polymer droplets) or as a stable dispersion (polymer beads). The beads or droplets have a particle size between approximately 50 nm and approximately 1 μm, preferably between approximately 70 nm and approximately 300 nm, as determined using a Brookhaven Model BI-90 particle size analyzer (Brookhaven Instruments Corp, Holtsville, USA). This particle size results in a characteristic translucent or milky appearance.

[0045]

[0044] The molecular weight of one or more acrylic resins is preferably between about 10,000 and 1,000,000 Daltons, more preferably between about 50,000 and 500,000 Daltons.

[0046]

[0045] In a particular embodiment, one or more acrylic resins are self-crosslinking resins. Self-crosslinking polymers further comprise one or more self-reactive functional groups. Crosslinking reactions typically occur when water is removed during drying or when the temperature rises above a given threshold. Certain self-crosslinking acrylic resins are made up of core-shell particles, where the hydrophobic (e.g., polystyrene) core comprises one or more self-crosslinking functional groups and the hydrophilic shell comprises (meth)acrylic acid groups, thus stabilizing the dispersion.

[0047]

[0046] During drying (generally using accelerating means such as a hot air oven or IR dryer), the water gradually evaporates, and the beads or droplets of one or more acrylic resins coalesce to form a film in which the IR absorbing material is stable. The lowest temperature at which the film can be formed is called the minimum film-forming temperature (MFFT), and is preferably close to or slightly above room temperature, so that a polymer film is formed when the coated substrate passes through the drying device. Since one or more acrylic resins can stabilize the IR absorbing material very effectively, the ratio of the dry amount of one or more acrylic resins to the amount of IR absorbing pigment is low, preferably between about 50:50 and about 75:25, and more preferably between about 60:40 and about 70:30. Thus, the security inks described herein can be printed as rather thin layers (typical dry layer thickness of about 3 μm to about 10 μm), but exhibit strong absorbance in the IR region. Furthermore, the resulting layers generally exhibit low gloss, effectively mimicking the inherently matte appearance of porous substrates such as trust cotton paper, making it even more difficult (as desired) to detect the resulting layers with the naked eye.

[0048]

[0047] Particularly preferred aqueous acrylic compositions are those known by DSM Neoresins as Neocryl® XK-98 (self-crosslinking resin), Neocryl® XK-16 (self-crosslinking resin), Neocryl® XK-237 (self-crosslinking resin), Neocryl® BT-100, and Neocryl® BT-20, and by BASF as Joncryl® 538, Joncryl® 1532, Joncryl® 1907, Joncryl® 1908, and Joncryl® 1984 (self-crosslinking resin). It is commercially available under the names (consisting of an emulsion / dispersion containing an anionic acrylic copolymer), NeoPac (trademark) E-180 by Covestro (consisting of an emulsion containing an aromatic urethane acrylic copolymer), NeoPac (trademark) E-200 by Covestro (consisting of an emulsion containing an aliphatic urethane acrylic copolymer), and Zinpol 350 and Zinpol 460 by Worlee (consisting of a dispersion / emulsion containing a styrene acrylic copolymer).

[0049]

[0048] At a pH (i.e., between about 7.0 and about 9.0) required to ensure sufficient stability of the security inks described herein, the (meth)acrylic groups of one or more acrylic resins are stabilized as acrylates by one or more neutralizing agents. The neutralizing agents may be inorganic bases, organic bases, or any combination thereof. Examples of inorganic bases, but not limited to, include alkali metal hydroxides (especially lithium, sodium, potassium, and magnesium), alkali metal carbonates, alkali metal bicarbonates, and alkali metal salts of inorganic acids, such as sodium borate (borax), sodium phosphate, sodium pyrophosphate, ammonia, and mixtures thereof. A preferred inorganic base is ammonia, for it is relatively inexpensive and its rapid evaporation is advantageous for rapid drying. Preferred organic bases are amines, such as triethanolamine, triethylamine, dimethylisopropylamine, N-methylethanolamine, N-methyldiethanolamine, N,N'-dimethylethanolamine, and 2-amino-2-methyl-1-propanol.

[0050]

[0049] In addition to the one or more acrylic resins described herein, the binder described herein may also contain up to 30% by weight, preferably up to 25% by weight, and more preferably up to 20% by weight, of one or more additional resins different from the acrylic resins, the weight percentage being based on the total weight of the binder; in other words, a portion of the acrylic resin may be replaced by one or more additional resins. The one or more resins described herein are water-soluble or water-dispersible resins, preferably water-dispersible resins, which can be selected from the group consisting of polyurethane, polyvinyl alcohol, polyamide and polyolefin. According to one embodiment, the one or more additional resins are polyurethane. As is known to those skilled in the art, the use of polyurethane resins improves the physical and chemical resistance of the security function obtained from the ink, and enhances the flexibility of the security function and its adhesion to substrates, particularly polymer and plastic substrates. When one or more polyurethane resins are to be used in combination with the acrylic resins described herein in the binder described herein, the binder must contain up to 30% by weight of the polyurethane resin, preferably up to 25% by weight, and more preferably up to 20% by weight. Any amount greater than this will negatively affect the stability of the ink during storage due to a progressive increase in viscosity.

[0051]

[0050] The security inks described herein contain about 0.125% to about 5.0% by weight of one or more zinc aluminum phosphate compounds, where the weight percentage is based on the total weight of the security ink, and the ratio R (ratio R = m(one or more zinc aluminum phosphate compounds) / [m(one or more zinc aluminum phosphate compounds) + m(one or more IR absorbing materials)]) of the amount of one or more zinc aluminum phosphate compounds to the sum of the amounts of one or more zinc aluminum phosphate compounds and one or more IR absorbing materials is between about 2.0 and about 20, preferably between about 2.5 and 20, and more preferably between about 2.5 and 10.

[0052]

[0051] Preferably, each of the one or more zinc aluminum phosphate compounds is an orthophosphate such as zinc aluminum orthophosphate, or a polyphosphate such as zinc aluminum polyphosphate, and includes their hydrates. Preferably, each of the one or more zinc aluminum phosphate compounds is zinc aluminum phosphate hydrate, preferably an orthophosphate or polyphosphate hydrate compound. The one or more zinc aluminum phosphate compounds may further contain molybdenum, calcium and / or strontium and / or silicon.

[0053]

[0052] One or more zinc aluminum phosphate compounds described herein independently contain about 20% to about 70% by weight of zinc, more preferably about 25% to about 65% by weight of zinc (the weight percentages are calculated from the weight percentage of ZnO in the compound and measured according to ISO 6745); and about 0.5% to about 20% by weight of aluminum, more preferably about 1% to about 15% by weight of aluminum (the weight percentages are calculated from the weight percentage of Al2O3 in the compound and measured by ICP); and about 10% to about 70% by weight of phosphorus, more preferably about 15% to about 60% by weight of phosphorus (P) (the weight percentages are calculated from the weight percentage of PO4 in the compound). 3- Alternatively, it is calculated from the weight percentage of P2O5, which is measured according to ISO 6745; preferably, it includes; the weight percentage is based on the total weight of the zinc aluminum phosphate compound.

[0054]

[0053] When calculated as a weight percentage of each element (as Zn, Al, and P), one or more zinc aluminum phosphate compounds described herein preferably contain independently about 15% to about 60% by weight of zinc (Zn), more preferably about 20% to about 55% by weight; about 0.3% to about 12% by weight of aluminum (Al), more preferably about 0.5% to about 8% by weight; and about 5% to about 30% by weight of phosphorus (P), more preferably about 6% to about 25% by weight; the weight percentage is based on the total weight of the zinc aluminum phosphate compound.

[0055]

[0054] Preferably, one or more zinc aluminum phosphate compounds have a particle size between about 0.5 microns and about 10 microns, more preferably between about 1 micron and about 5 microns.

[0056]

[0055] Suitable zinc aluminum phosphate compounds are commercially available from Heubach under the names HEUCOPHOS® ZAM-Plus (organically modified zinc aluminum molybdenum orthophosphate hydrate), HEUCOPHOS® ZCP-Plus (zinc calcium strontium aluminum orthophosphate hydrate), HEUCOPHOS® ZAPP (zinc aluminum polyphosphate hydrate), and HEUCOPHOS® ZPA (zinc aluminum orthophosphate hydrate).

[0057]

[0056] The security inks described herein may further include one or more additives selected from fillers, waxes, surfactants, defoamers, thickeners and mixtures thereof.

[0058]

[0057] The security inks described herein may further contain one or more fillers, provided that these promising additional fillers or extenders do not negatively interfere with the absorption in the IR / NIR spectrum for the purpose of the machine-readable security function and do not negatively interfere with their optical properties. The one or more fillers described herein are preferably selected from the group consisting of carbon fibers, talc, mica (muscovite), wollastonite, calcined clay, earthenware, kaolin, carbonates (e.g., calcium carbonate, sodium aluminum carbonate), silica and silicates (e.g., magnesium silicate, aluminum silicate), sulfates (e.g., magnesium sulfate, barium sulfate), titanates (e.g., potassium titanate), hydrated alumina, silica, fumed silica, montmorillonite, graphite, anatase, rutile, bentonite, vermiculite, zinc white, zinc sulfide, wood flour, quartz flour, natural fibers, synthetic fibers, and combinations thereof. Alternatively, for the purpose of not impairing the optical properties of the machine-readable security features described herein, one or more microspheres or hollow spheres made of polymers (e.g., polystyrene or PMMA) or glass may be used as fillers. If present, one or more fillers are preferably present in an amount of about 0.01 to about 10% by weight, preferably about 0.1 to about 5% by weight, where the weight percentage is based on the total weight of the security ink.

[0059]

[0058] The security inks described herein may further contain, preferably, one or more waxes selected from the group consisting of synthetic waxes, petroleum waxes, and natural waxes. Preferably, one or more waxes are selected from the group consisting of microcrystalline waxes, paraffin waxes, polyethylene waxes, polyamide waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, pulverized PTFE-modified polyethylene waxes, Fischer-Tropsch waxes, silicone fluids, beeswax, candelilla wax, montan wax, carnauba wax, and mixtures thereof. If present, one or more waxes are preferably present in an amount of about 0.1 to about 3% by weight, the weight percentage being based on the total weight of the security ink.

[0060]

[0059] The security inks described herein may further comprise one or more thickeners for modifying the fluid properties of the security inks described herein. Natural thickeners include, but are not limited to, xanthan gum, alginic acid and its salts (especially sodium alginate), gar gum, locust bean gum, agar, carboxymethylcellulose, hydroxyethylcellulose, pectin, casein, gelatin, and carrageenan. Synthetic thickeners include, but are not limited to, hydrophobic ethoxylated urethane resins (HEUR), hydrophobic modified polyethers (HMPE), alkali-swelling emulsions (ASE), hydrophobic modified alkali-swelling emulsions (HASE), polyacrylamide, polyethylene oxide, polyvinylpyrrolidone, polyvinyl methyl ether, and polyether polyol compounds. Suitable thickeners include those manufactured by Elementis under the names RHEOLATE® 212, RHEOLATE® 255, RHEOLATE® 278 TF, RHEOLATE® HX 6008, and RHEOLATE® HX 6010; those manufactured by BYK under the names RHEOBYK®-T 1000 VF, RHEOLATE®-T 1010 VF, RHEOLATE®-L 1400 VF, RHEOLATE®-HV 80, and RHEOLATE®-M 2600 VF; and those manufactured by BASF under the names RHEOVIS® AS 1130, RHEOVIS® PU 1190, RHEOVIS® PU 1214, RHEOVIS® PU 1291, RHEOVIS® PU 1331, RHEOVIS® PU 1341, and RHEOVIS® PE It is marketed under the names 1330 and Leovis® PE 1331, and by Tiarco Chemicals under the names Paragum 500, Paragum 530, and Paragum 600. If present, one or more thickeners are preferably present in an amount of about 0.05 to about 5% by weight, more preferably about 0.1 to about 3% by weight, where the weight percentage is based on the total weight of the security ink.

[0061]

[0060] The security inks described herein may further comprise one or more iridescent pigments. Typical examples of iridescent pigments include, but are not limited to, interference-coated pigments comprising synthetic or natural mica coated with one or more layers made of metal oxides (e.g., titanium oxide, zirconium oxide, tin oxide, chromium oxide, nickel oxide, copper oxide, iron oxide and iron oxide / hydroxide), other layered silicates (e.g., talc, kaolin and sericite), glass (e.g., borosilicate), silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum oxide / hydroxide (boehmite), and nuclei made from mixtures thereof. The structures described above are, for example, described in Chem. Rev. 99 (1999), G. Pfaff and P. Reynders, pp. 1963–1981 and International Publication No. 2008 / 083894A2. Typical examples of these interference-coated pigments include, but are not limited to, silicon oxide nuclei coated with one or more layers made of titanium oxide, tin oxide and / or iron oxide; natural or synthetic mica nuclei coated with one or more layers made of titanium oxide, silicon oxide and / or iron oxide, particularly mica nuclei coated with alternating layers made of silicon oxide and titanium oxide; borosilicate nuclei coated with one or more layers made of titanium oxide, silicon oxide and / or tin oxide; and titanium oxide nuclei coated with one or more layers made of iron oxide, iron oxide / hydroxide, chromium oxide, copper oxide, cerium oxide, aluminum oxide, silicon oxide, bismuth vanadate, nickel titanate, cobalt titanate and / or antimond-doped, fluorine-doped, or indium-doped tin oxide; and aluminum oxide nuclei coated with one or more layers made of titanium oxide and / or iron oxide.

[0062]

[0061] The security inks described herein may include one or more additional IR absorbers known in the art. The role of the additional IR absorbers may be to slightly modify the reflectance profile of the machine-readable security feature to fully conform to the specifications of the detection system.

[0063]

[0062] The one or more further IR absorbers include a) one or more transition elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, and Ni, and a phosphate (PO4 3- ), hydrogenophosphate (HPO4 2- ), pyrophosphate (P2O7 4- ), metaphosphate (P3O9 3- ), polyphosphate, silicate (SiO4 4- ), condensed polysilicate; titanate (TiO3 2- ), condensed polytitanate, vanadate (VO4 3- ), condensed polyvanadate, molybdate (MoO4) 2- ), condensed molybdate, tungstate (WO4 2- ), condensed polytung state, niobate (NbO3 2- ), fluoride (F - ), chloride (Cl - ), sulfate (SO4 2- ) and / or hydroxyl (OH - a) A compound comprising one or more anions selected from the group consisting of ) ); b) an inorganic compound selected from the group consisting of doped tin oxide, doped indium oxide, reduced tungsten oxide, and tungsten bronze; c) an organic compound selected from the group consisting of phthalocyanine compounds, naphthalocyanine compounds, dithiolene compounds, and lylene-based compounds; and d) a mixture thereof. If present, the amount of one or more additional IR absorbers is preferably about 0.5% to about 25% by weight, where the weight percentage is based on the total weight of the security ink. The ratio between the one or more additional IR absorbers, if present, and the total of all IR absorbers is preferably between about 0.1% to about 30% by weight, more preferably between about 1% to about 15% by weight.

[0064]

[0063] According to one embodiment, at least one of one or more further IR absorbers is doped tin oxide, in which case the tin oxide is preferably doped with antimony (antimony tin oxide, ATO), in which case the antimony is present in an amount of about 0.5 to about 20 mol%, preferably about 2 to about 18 mol%.

[0065]

[0064] According to another embodiment, at least one of one or more further IR absorbers is doped indium oxide, in which case the indium oxide is preferably doped with tin (indium tin oxide, ITO), in which case the tin is present in an amount of about 1 to about 30 mol%, preferably about 5 to about 15 mol%. Preferably, reduced indium tin oxide is used as one or more further IR absorbers. The level of reduction is preferably between about 0.1 mol% and about 5 mol%, more preferably between about 0.5 mol% and about 1 mol%, where a reduction level of 1 mol% means that oxygen atoms have been removed from 1% of the indium tin oxide units.

[0066]

[0065] According to another embodiment, at least one of one or more further IR absorbers is reduced tungsten oxide, and / or at least one of one or more further IR absorbers is tungsten bronze. Reduced tungsten oxide has the general formula W y O z These are non-stoichiometric compounds, where the ratio z / y is less than 3 and greater than 2, preferably less than 2.99 and greater than 2.2, more preferably less than 2.9 and greater than 2.7. Such compounds are described, for example, in H. Takeda and K. Adachi, J. Am Ceram. Soc., 90

[12] , 2007, pp. 4059-4061, U.S. Patent Application Publication No. 2006 / 0178254 and U.S. Patent Application Publication No. 2007 / 0187653.

[0067]

[0066] Tungsten bronzes are non-stoichiometric compounds obtained from stoichiometric tungsten oxide WO3 or tungstate MWO4. The formula M x W y O z tungsten bronzes are described, for example, in US Patent Application Publication No. 2006 / 0178254 and US Patent Application Publication No. 2007 / 0187653. US Patent Application Publication No. 2006 / 0178254 discloses M x W y O z where 0.001 ≦ x / y ≦ 1 and 2.2 ≦ z / y ≦ 3.0. US Patent Application Publication No. 2007 / 0187653 discloses M x W y O z where 0.001 ≦ x / y ≦ 1.1 and 2.2 ≦ z / y ≦ 3.0. M is at least one element selected from the group consisting of H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi and I, preferably Na, Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe and Sn.

[0068]

[0067] The tungsten bronzes of the formula M x WO3 are described, for example, in US Patent Application Publication No. 2006 / 0178254 and US Patent Application Publication No. 2007 / 0187653, where M is a metal element, such as an alkali metal, an alkaline earth metal or a rare earth metal, and 0 < x < 1. Such a compound with M = K is also described in C. Guo et al., ACS Appl. Mater. Interfaces, 3, 2011, pages 2794 - 2799 and has been shown to exhibit strong absorption beyond 900 nm.

[0069]

[0068] The formula M E A G W (1-G) OJ The tungsten bronzes are described, for example, in U.S. Patent Application Publication No. 2007 / 0187653, where M is one or more elements selected from H, He, alkali metals, alkaline earth metals, rare earth elements, Mg, Zr, Cr, Mn, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Tl, Si, Ge, Sn, Pb, Sb, B, F, P, S, Se, Br, Te, Ti, Nb, V, Mo, Ta, Re, Be, Hf, Os, Bi, and I; A is one or more elements selected from Mo, Nb, Ta, Mn, V, Re, Pt, Pd, and Ti; W is tungsten; O is oxygen; 0 < E ≦ 1.2; 0 < G ≦ 1; and 2 ≦ J ≦ 3.

[0070]

[0069] U.S. Patent Application Publication No. 2011 / 0248225 discloses, for example, a potassium cesium tungsten bronze solid solution of the formula K x Cs y WO z where x + y ≦ 1 and 2 ≦ z ≦ 3. Such compounds have been shown to be strong absorbers in the region of 1200 - 1750 nm.

[0071]

[0070] Suitable examples of phthalocyanine compounds and naphthalocyanine compounds are disclosed in European Patent No. 0 799 831B1 and European Patent No. 3 140 352B. Suitable examples of dithiolene compounds are disclosed in European Patent No. 2 101 986B. Suitable examples of rylene-based compounds are disclosed in International Publication No. 2010 / 112452A1, European Patent No. 1 879 847B, and European Patent No. 1 874 773B.

[0072]

[0071] The security ink described herein may further include one or more luminescent compounds, for example, to provide enhanced forgery resistance for security functions.

[0073]

[0072] The security inks described herein may further comprise one or more marker substances or tagants.

[0074]

[0073] The security inks described herein may further include one or more additives, which include, but are not limited to, compounds and materials used to adjust the physical, fluid and chemical parameters of the security ink, such as consistency (e.g., anti-settling agents and plasticizers), foaming properties (e.g., defoaming agents and deaeration agents), lubricity (waxes), UV stability (light stabilizers), adhesion, and surface properties (wetting agents, oleophobic and hydrophobic agents). The additives described herein may be present in the security inks described herein in amounts known in the art and in forms including so-called nanomaterials in which at least one of the dimensions of the additive is in the range of 1 to 1000 nm.

[0075]

[0074] The security inks described herein may further contain one or more crosslinking agents to further enhance the mechanical resistance of the machine-readable security function obtained thereby. The crosslinking agents have functional groups that can react with the carbonyl groups of one or more acrylic resins and strengthen the polymer network. Typically, the reaction begins when heat treatment (such as hot air or an IR dryer) is applied to the security function. Examples of crosslinking agents include, but are not limited to, organic chelates of titanium or zirconium, polycarbodiimide compounds (e.g., CX-300 sold by DSM NeoResins), polyaziridine compounds (e.g., CX-100 sold by DSM NeoResins), polyoxazoline compounds, amino resins (e.g., melamine-formaldehyde), blocked isocyanates, silane compounds, polyglycidyl ether compounds, and epoxysiloxane compounds (e.g., CoatOSil® 1770 sold by Momentive Performance Materials and Dynasylan® GLYMO sold by Evonik Industries).

[0076]

[0075] The present invention further provides a method for producing security ink as described herein, and security ink obtained therefrom.

[0077]

[0076] The security ink described herein is i) A step of mixing and / or dispersing one or more zinc aluminum phosphate compounds in water at room temperature, ii) Following step i), the mixture obtained in step i) is mixed and / or dispersed with one or more IR absorbing materials, preferably at room temperature, to form a dispersion. iii) Preferably, the dispersion obtained in step ii) is filtered and dried at a temperature of at least 50°C for 24 hours to obtain the surface-treated IR-absorbing material as a solid powder. iii) Following step ii), the solid powder obtained in step iii) is mixed and / or dispersed with a mixture containing water, a binder containing one or more acrylic resins, and an optional additive, preferably at room temperature. It can be prepared by [method].

[0078]

[0077] The security ink described herein is i) A step of mixing and / or dispersing one or more IR absorbing materials and one or more zinc aluminum phosphate compounds described herein in water, preferably at room temperature, to produce an IR absorbing material surface-treated with the one or more zinc aluminum phosphate compounds, ii) Following step i), preferably for 24 hours at a temperature of at least 50°C, the dispersion obtained in step i) is filtered and dried to obtain the surface-treated IR-absorbing material as a solid powder. iii) Following step ii), the solid powder obtained in step ii) is mixed and / or dispersed with a mixture containing water, a binder containing one or more acrylic resins, and an optional additive, preferably at room temperature. It can be prepared by [method].

[0079]

[0078] Alternatively, the security inks described herein are: i) A step of mixing one or more IR absorbing materials with one or more zinc aluminum phosphate compounds to produce a solid powder of the well mixed compounds, ii) The powder obtained in step i) is mixed and / or dispersed with a binder containing one or more acrylic resins, preferably at room temperature, to form a dispersion. iii) Following step ii), the dispersion obtained in step ii) is mixed and / or dispersed with water and an optional additive, preferably at room temperature. It can be prepared by [method].

[0080]

[0079] Alternatively, the security inks described herein are i) A step of mixing and / or dispersing a binder containing one or more zinc aluminum phosphate compounds and one or more acrylic resins, preferably at room temperature, to form a dispersion; ii) Following step i), a step of mixing and / or dispersing the dispersion obtained in step i) with one or more IR absorbing materials, preferably at room temperature, iii) Following step ii), the dispersion obtained in step ii) is mixed and / or dispersed with water and an optional additive, preferably at room temperature. It can be prepared by [method].

[0081]

[0080] As an alternative, the security inks described herein are i) A step of mixing and / or dispersing one or more zinc aluminum phosphate compounds in water, preferably at room temperature, ii) Following step i), a step of mixing and / or dispersing the dispersion obtained in step i) with one or more IR absorbing materials, preferably at room temperature, iii) Following step ii), preferably for 24 hours at a temperature of at least 50°C, the dispersion obtained in step ii) is filtered and dried to obtain the surface-treated IR-absorbing material as a solid powder. iv) Following step iii), the solid powder obtained in step iii) is mixed and / or dispersed with a binder containing one or more acrylic resins, preferably at room temperature, to obtain a dispersion. iv) Following step iv), the dispersion obtained in step iv) is mixed and / or dispersed with water and an optional additive, preferably at room temperature. It can be prepared by [method].

[0082]

[0081] The security ink described herein is applied to the substrate described herein, preferably by a screen printing process described herein, to generate a machine-readable security function.

[0083]

[0082] Screen printing (also known in the art as silkscreen printing) is typically a printing technique that uses a screen made of woven mesh to support an ink-blocking stencil. The attached stencil forms openings in the mesh that transfer ink to the substrate as a sharp-edged image. A squeegee moves across the screen having the ink-blocking stencil, allowing the ink to pass through the threads of the woven mesh within the openings. Generally, the screen is made of a piece of porous fine woven fabric called mesh stretched on, for example, an aluminum or wooden frame. Currently, most meshes are made of synthetic or artificial materials such as steel yarn. Preferred synthetic materials are nylon or polyester yarn.

[0084]

[0083] In addition to screens made from woven meshes based on synthetic or metallic threads, screens have also been developed from solid metal sheets having a grid of holes. Such screens are prepared by a process that includes electrolytically forming a metal screen by forming a screen framework on a matrix with a separating agent in a first electrolytic bath, peeling the formed screen framework from the matrix, and subjecting the screen framework to electrolysis in a second electrolytic bath to deposit metal onto the framework.

[0085]

[0084] There are three types of screen printing machines: flatbed, cylinder, and rotary screen printing machines. Flatbed and cylinder screen printing machines are similar in that they both use a flat screen and a three-step reciprocating process to perform the printing operation. First, the screen is moved to a position over the substrate, then the squeegee is pressed against the mesh and pulled onto the image area, and then the screen is lifted from the substrate to complete the process. In a flatbed printing machine, the substrate to be printed is typically placed on a horizontal printing bed parallel to the screen. The substrate is attached to the cylinder by cylinder pressurization. Flatbed and cylinder screen printing processes are discontinuous processes and as a result are generally limited to a maximum speed of 45 m / min for webs or 3,000 sheets / hour for sheet feeding processes.

[0086]

[0085] Conversely, rotary screen printing machines are designed for continuous high-speed printing. The screens used in rotary screen printing machines are thin-walled metal cylinders, for example, typically obtained using the electroforming method described above, or made from woven steel yarn. The open-end cylinders are capped at both ends and mounted on a block on the side of the printing machine. During printing, ink is pumped to one end of the cylinder to maintain a constant supply of fresh ink. A squeegee is fixed inside the rotating screen, and the squeegee pressure is maintained and adjusted to allow for good and consistent print quality. The advantage of rotary screen printing machines is their speed, which can easily be reached at 150 m / min in the web or 10,000 sheets / hour in the sheet feeding process.

[0087]

[0086] Screen printing is further described, for example, in The Printing Ink Manual, RHLeach and RJPierce, Springer Edition, 5th edition, pp. 58-62; Printing Technology, JMAdams and PADolin, Delmar Thomson Learning, 5th edition, pp. 293-328; and Handbook of Print Media, H. Kipphan, Springer, pp. 409-422 and 498-499.

[0088]

[0087] The present invention further provides a method for generating a machine-readable security function as described herein, and a machine-readable security function obtained thereby. The method includes step a) applying a security ink as described herein to a substrate as described herein by a printing process selected from the group consisting of gravure printing, flexographic printing and screen printing, more preferably by screen printing as described herein. After the printing step is carried out, step b) is performed to dry the security ink in the presence of hot air, infrared radiation, or a combination thereof, thereby forming a machine-readable security function as described herein on the substrate, the drying step being performed after step a). Preferably, step b) of drying the security ink as described herein is carried out for about 30 seconds to about 2 minutes, preferably at a temperature between about 20°C (room temperature) and about 70°C. The time between step a) (i.e., step a) of screen printing) and step b) (i.e., step b) of drying) is preferably between about 0.1 seconds and about 10 seconds, more preferably between about 0.1 seconds and about 5 seconds, and even more preferably between about 0.5 seconds and about 2 seconds.

[0089]

[0088] The present invention further provides a machine-readable security function made with the security ink described herein on the substrate described herein.

[0090]

[0089] The machine-readable security features comprising one or more IR-absorbing materials described herein may consist of a mark, which means a discontinuous layer of patterns including, but not limited to, symbols, alphanumeric symbols, motifs, letters, phrases, numbers, logos, and figures. Preferably, the mark is selected from the group consisting of codes, symbols, alphanumeric symbols, motifs, geometric patterns (e.g., circles, triangles, and regular or irregular polygons), letters, phrases, numbers, logos, figures, portraits, and combinations thereof. Examples of codes include coded marks, e.g., coded alphanumeric data, one-dimensional barcodes, two-dimensional barcodes, QR codes, and data matrices.

[0091]

[0090] According to one embodiment, the substrate described herein is preferably selected from the group consisting of paper or other fibrous materials (including woven and nonwoven fibrous materials), for example, cellulose and paper-containing materials. Typical paper, paper-like or other fibrous materials are made from a variety of fibers, but are not limited to Manila hemp, cotton, linen, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton / linen blends are preferred for banknotes, while wood pulp is commonly used in security documents other than banknotes. As is well known to those skilled in the art, the substrate may contain further additives known to those skilled in the art, such as fillers, sizing agents, whitening agents, processing aids, reinforcing agents or wet strength enhancers. In another embodiment, the substrates described herein are preferably made from plastic and polymer materials, such as polyethylene (PE), polypropylene (PP, e.g., oriented polypropylene (OPP, uniaxially oriented transversely), biaxially oriented polypropylene (BOPP, oriented longitudinally and transversely), and uniaxially oriented polypropylene (MOPP, uniaxially oriented longitudinally)), polyamide (PA), polyester, e.g., poly(ethylene terephthalate) (PET), polyethylene terephthalate glycol modified (PETG) including poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate), poly(1,4-butylene terephthalate) (PBT), poly(ethylene 2,6-naphthoate) (PEN), and polyvinyl chloride (PVC). When the substrates are made from plastic and polymer materials, one or more opacifying layers may be present on their surfaces.

[0092]

[0091] The machine-readable security features described herein are advantageous in that they exhibit high reflectivity in the visible range and low reflectivity in the infrared or near-infrared range, thus enabling efficient authentication and recognition by standard devices and standard detectors, including those characterizing high-speed banknote sorting machines, because such detectors rely on the difference in reflectivity at selected wavelengths in the Vis and IR ranges. In particular, the security inks described herein enable the production of colorless or slightly colored machine-readable security features, i.e., machine-readable security features having the following optical properties: a lightness L equal to or higher than about 80 (preferably equal to or higher than about 85, more preferably equal to or higher than about 90) * , higher than approximately -3.0 (preferably higher than approximately -2.7, and more preferably higher than approximately -2.5) * The value is lower than approximately 8.5 (preferably lower than approximately 7.5, and more preferably lower than approximately 6.5). * The value and reflectance at 900 nm that is lower than or equal to about 60% (preferably lower than or equal to about 55%, more preferably lower than or equal to about 45%). As described herein, the L of the machine-readable security function. * a * and b * The value was measured according to CIELAB (1976), a * and b * These are color coordinates in Cartesian two-dimensional space (a * = Color values ​​along the red / green axis, b * =Color values ​​along the blue / yellow axis), L * a * b *The values ​​are obtained independently with a Datacolor DC45IR spectrophotometer (measurement geometry: 45 / 0°; spectral analyzer: patented dual-channel holographic grating; 256-photodiode linear array used for both reference and sample channels; light source: full-bandwidth LED illumination). To avoid affecting the measurement, the substrate must have an IR reflectance higher than the machine-readable security feature (this applies to most uncolored security substrates).

[0093]

[0092] As described herein, the reflectance at 900 nm of the machine-readable security features described herein can be measured with a Datacolor DC45IR spectrophotometer, and a reflectance of 100% can be measured using the device's internal standard.

[0094]

[0093] Security documents, particularly banknotes, are produced using continuous printing processes employing various printing techniques. In particular, banknote substrates are subjected to several different types of printing processes in succession, and once each is completed, the next step is applied thereafter, incurring considerable general costs in terms of handling and storage. The colorless or slightly colored machine-readable security features described herein can be advantageously incorporated into and / or on security documents, allowing for freedom in the design of subsequent security printing steps. For example, the security ink described herein may be applied by a substrate manufacturer as the first step of a known security document multiplex printing step to form a colorless or slightly colored machine-readable security feature preferably having the shape of one or more seals as described herein. Subsequently, a security printing press may generate one or more additional security features by, for example, offset and intaglio printing processes, the features partially or completely covering the machine-readable security features described herein. Preferably, the additional security features are prepared from an IR transparent ink, i.e., an ink that exhibits low reflectivity in a portion of the visible spectrum and high reflectivity in the near-IR region, as shown in Figure 1.

[0095]

[0094] For the purpose of further increasing the security level of security documents and their resistance to forgery and illegal copying, the substrates described herein may include printed, coated, or laser-marked or laser-perforated seals, watermarks, security threads, fibers, planchettes, luminescent compounds, windows, foils, decals, primers, and two or more combinations thereof, provided that these potential additional functions or elements do not negatively interfere with the absorbance in the relevant IR / NIR range spectrum of the machine-readable security function and do not negatively interfere with the optical properties described herein of the machine-readable security function described herein.

[0096]

[0095] For the purpose of increasing durability against soiling or chemical resistance and cleanability, and consequently the circulation lifespan of the security document, or for the purpose of modifying its aesthetic appearance (e.g., optical gloss), one or more protective layers may be applied to the machine-readable security features or security documents described herein. If present, one or more protective layers are typically made of a protective varnish that is transparent or may be slightly colored or tinted, and may have some degree of gloss. The protective varnish may be a radiation-curable composition, a heat-curing composition, or any combination thereof. Preferably, one or more protective layers are made of a radiation-curable composition, more preferably a UV-Vis-curable composition.

[0097]

[0096] The machine-readable security features described herein may be provided directly on a substrate on which the security features are to remain permanently (for example, in banknote applications). In some cases, the machine-readable security features described herein may be generated on an auxiliary substrate, such as a security thread, security stripe, foil, decal, window, or label, and consequently transferred to a security document in a separate step. Alternatively, the machine-readable security features may also be provided on a temporary substrate for generation, from which the machine-readable security features are subsequently removed. After the solidification / curing of the security ink described herein for generating the machine-readable security features, the temporary substrate may be removed from the machine-readable security features.

[0098]

[0097] Alternatively, in another embodiment, the adhesive layer may be present on top of the machine-readable security feature or on a substrate having the machine-readable security feature described herein, wherein the adhesive layer is on the substrate opposite to the side on which the machine-readable security feature is provided, or on the machine-readable security feature on the same side as the machine-readable security feature. Thus, the adhesive layer may be applied to the machine-readable security feature or to the substrate, and the adhesive layer is applied after the drying or curing step is completed. Such articles may be attached to all kinds of documents or other articles or items without printing or other processes involving machinery and somewhat higher labor. Alternatively, the substrate having the machine-readable security feature described herein may be in the form of a transfer foil that can be applied to a document or article in a separate transfer step. For this purpose, the substrate is provided with a release coating on which the machine-readable security feature is generated as described herein. One or more adhesive layers may be applied on top of the machine-readable security feature thus generated.

[0099]

[0098] Substrates, security documents, decorative elements and objects having more than one, i.e., two, three, four, etc., machine-readable security features as described herein are also described herein. Articles having machine-readable security features as described herein, in particular security documents, decorative elements or objects are also described herein.

[0100]

[0099] As described above, the machine-readable security features described herein may be used for the protection and authentication of security documents or decorative elements.

[0101]

[0100] Security documents include, but are not limited to, documents of value and goods of value. Typical examples of documents of value include, but are not limited to, banknotes, certificates, tickets, checks, vouchers, revenue stamps and tax indications, contracts and similar documents, identification documents such as passports, ID cards, visas, driver's licenses, bank cards, credit cards, transaction cards, access documents or cards, admission tickets, public transport tickets, graduation certificates or title deeds and similar documents, preferably including banknotes, identification documents, documents granting rights, driver's licenses and credit cards. The term "goods of value" refers particularly to cosmetics, nutritional supplements, medical supplies, alcohol, tobacco products, beverages or foodstuffs, electrical / electronic articles, spare parts (e.g., for automobiles, aircraft or electronic applications), textiles or jewelry, i.e., packaging materials for articles that should be protected from counterfeiting and / or illegal reproduction in order to guarantee the contents of the packaging of, for example, genuine drugs or spare parts. Examples of these packaging materials include, but are not limited to, labels, e.g., authentication brand labels, tamper-evident labels and seals. The disclosed substrates, valuable documents, and valuable goods are shown solely for illustrative purposes and are not intended to limit the scope of the present invention.

[0102]

[0101] The present invention further provides a method for authenticating a security document, comprising: a) preparing a security document as described herein, which is made of one of the security inks listed herein and has a machine-readable security function; b) illuminating the machine-readable security function with at least one wavelength in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1200 nm); c) detecting the optical properties of the machine-readable security function by detecting light reflected and / or transmitted by the machine-readable security function at at least one wavelength, wherein the at least one wavelength is in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1200 nm); and d) determining the authenticity of the security document from the detected optical properties of the machine-readable security function.The present invention relates to a method for authenticating a security document, comprising the steps of: a) preparing a security document as described herein, having a machine-readable security function made of a security ink as described herein; and b) illuminating the machine-readable security function with at least two wavelengths, one of which is in the visible range (400 to 700 nm) and the other of which is in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1200 nm). The present invention also provides a method comprising: c) detecting the optical properties of a machine-readable security function by detecting light reflected and / or transmitted by the machine-readable security function at at least two wavelengths, wherein one of the at least two wavelengths is in the visible range and the other of the at least two wavelengths is in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1200 nm); and d) determining the authenticity of a security document from the detected optical properties of the machine-readable security function.

[0103]

[0102] Authentication of a machine-readable security feature made with security ink as described herein may be performed using an authentication device comprising one or more light sources, one or more detectors, an analog-to-digital converter, and a processor. The machine-readable security feature is illuminated simultaneously or subsequently by one or more light sources; one or more detectors detect the light reflected or transmitted by the machine-readable security feature and output an electrical signal proportional to the light intensity; the analog-to-digital converter converts the signal into digital information which is compared with a reference value stored in a database by the processor. The authentication device then outputs a positive signal of authenticity (i.e., the machine-readable security feature is genuine) or a negative signal (i.e., the machine-readable security feature is fake).

[0104]

[0103] According to one embodiment, the authentication device comprises a first source (such as a VIS LED) that emits light at a first wavelength in the visible range, a second source (such as an IR LED) that emits light at a second wavelength in the IR range, and a broadband detector (such as a photomultiplier tube). The first and second sources emit light at time intervals, causing the broadband detector to output signals corresponding to the VIS and IR emissions separately. These two signals can be compared separately (the VIS signal with a VIS reference value, and the IR signal with an IR reference value). Alternatively, these two signals may be converted into difference (or ratio) values, and the difference (or ratio) values ​​may be compared with difference (or ratio) reference values ​​stored in a database. The signals may be read by reflection and / or transmission.

[0105]

[0104] According to another embodiment of the detector unit, for the purpose of increasing the operating speed, the detector may include two detectors (such as a Si photodiode for the visible range and an InGaAs photodiode for the IR range) that are particularly suited to the emission wavelengths of the first and second sources. The first and second sources emit light simultaneously, and the two detectors simultaneously detect the light reflected or transmitted by the security function, and the two signals (or their difference or ratio) are compared with a reference value stored in a database.

[0106]

[0105] According to another embodiment, for the purpose of increasing resistance to counterfeiting, the authentication device comprises a source that emits light at multiple wavelengths (i.e., two, three, etc.) in the VIS range and multiple wavelengths (i.e., two, three, etc.) in the IR range. The source is activated sequentially, and the light reflected or transmitted by the machine-readable security function is detected by a broadband detector (such as a photomultiplier tube). The signals corresponding to the multiple emission wavelengths are then processed into a complete spectrum, which is compared with a reference spectrum stored in a database.

[0107]

[0106] According to another embodiment, for the purpose of increasing resistance to counterfeiting and increasing operating speed, the authentication device comprises a broadband continuous light source (such as a tungsten, tungsten halogen, or xenon lamp), a collimation unit, a diffraction grating, and a detector array. The diffraction grating is placed in the optical path after the machine-readable security function, and the light reflected or transmitted by the machine-readable security function is focused onto the grating by the collimation unit (usually made from a series of lenses and / or adjustable slits). The detector array is made up of multiple detection elements, each of which is sensitive to a specific wavelength. In this way, signals corresponding to the light intensity at multiple wavelengths are obtained simultaneously, processed as a complete spectrum, and compared with a reference spectrum in a database.

[0108]

[0107] In another embodiment, for the purpose of obtaining a two-dimensional image of the machine-readable security function described herein, the detector may be a CCD or CMOS sensor. In this case, the detectable wavelength range is about 400 nm to about 1100 nm (this is the upper detection limit for silicon sensors). The machine-readable security function is illuminated sequentially at at least two wavelengths, one of which is in the visible range and the other is in the IR range reachable by the CCD or CMOS detector. Alternatively, the CCD or CMOS sensor may include a filter layer such that individual pixels of the sensor are sensitive to different limited regions of the visible and IR spectra. In this case, it is possible to obtain a two-dimensional image of the machine-readable security function simultaneously at at least two wavelengths, one in the visible range and the other in the IR range reachable by the CCD or CMOS detector. The two-dimensional image is then compared with a reference image stored in a database.

[0109]

[0108] Optionally, the authentication device may include one or more light diffusing elements (such as capacitors), one or more lens assemblies (such as focusing or collimating lenses), one or more slits (adjustable or non-adjustable), one or more reflective elements (such as mirrors, particularly semi-transparent mirrors), one or more filters (such as polarizing filters), and one or more optical fiber elements.

[0110]

[0109] Those skilled in the art may conceive of several modifications to the specific embodiments described above without departing from the spirit of the present invention. Such modifications are included in the present invention.

[0111]

[0110] Furthermore, all documents referenced throughout this specification are incorporated by reference in their entirety so as to be fully described herein.

[0112] [Examples]

[0111] The present invention will now be described in more detail with reference to non-limiting examples. The following examples provide further details for preparing and using security inks for printing machine-readable security functions, the security inks independently comprising an IR-absorbing material consisting of copper hydroxide phosphate Cu2PO4(OH) (CAS-No 12158-74-6) having a copper phosphate crystal structure, particle sizes d50 of 2.0-2.6 μm and d98 of 7.5-12.0 μm. Laser diffraction was used to determine the d50 and d98 values ​​(instrument: (Cilas 1090); sample preparation: the IR-absorbing material was added to distilled water until the laser obscuration reached an operating level of 13-15%, and the measurements were performed according to ISO standard 13320). A. Solvent-based heat-drying screen printing security ink C0 (See Example E3 in International Publication No. 2020 / 239740A1) Solvent-based ink C0 contains the following components: Neoacrylic® B-728 (DSM Neoresins): Acrylic acid homopolymer, MW approx. 65000 g / mol (CAS not available), 17.6% by weight 2-Butoxyethyl acetate (Brenntag-Schweizer, CAS No. 112-07-2) 45.3% by weight Ethyl 3-ethoxypropionate acetate (Brenntag-Schweizer, CAS No. 763-69-9) 14.9% by weight Dowanol (trademark) DPM (Dow Chemicals): (2-Methoxymethylethoxy)propanol (CAS no. 34590-94-8) 6.6% by weight BYK(registered trademark)-1752(BYK): Silicone-free defoaming agent (CAS number unavailable) 3.3% by weight Aerosil (registered trademark) 200 (Evonik): Silicon dioxide (CAS no. 7631-86-9) 0.3% by weight Cu2PO4(OH)(12158-74-6) 12.0% by weight as described above in this specification.

[0113]

[0112] All components of the solvent-based security ink C0, except for the IR absorbing material Cu2PO4(OH), were mixed and dispersed at room temperature using a Dispermat (LC55) at 1000 rpm for 15 minutes. The IR absorbing material was then added and dispersed at 1000 rpm for 15 minutes to obtain the solvent-based security ink C0. The solvent-based security ink C0 had a viscosity of 1200 mPas, which was measured immediately after the preparation of the ink using a Brookfield viscometer ("RVDV-I Prime" model, spindle 27 at 100 rpm) with a 15 g sample of the solvent-based security ink C0 at 25°C.

[0114]

[0113] 30 g of solvent-based security ink C0 was placed in a 50 ml centrifuge tube (VWR® CT 50 ml) and stored in an oven (HERAEUS T6060) at 40°C for 30 days to simulate aging at room temperature for approximately 4 months. The ink was cooled to room temperature before applying it to the substrates described later herein.

[0115]

[0114] The solvent-based security ink C0 was manually applied using a semi-automatic coater (K control coater, model 001, manufactured by RK print) equipped with a bar coating #3 (theoretical thickness of approximately 24 μm) to a trust paper piece (BNP paper manufactured by Louisenthal, 100 g / m 2 , 14.5 cm × 17.5 cm), and then dried with a hot air dryer at a temperature of approximately 50°C for about 1 minute to form a machine-readable security function in the form of a dried coating having a thickness of 6 - 10 μm. The function had a size of 10 cm × 13 cm.

[0116] (Optical properties of the security function obtained from the solvent-based security ink C0)

[0115] The L * , a * and b * values of the security function obtained from the solvent-based security ink C0 were obtained from the measurement of the security function according to CIELAB (1976), where L * is lightness, and a * and b * are color coordinates in the Cartesian two-dimensional space (a * = color value along the red / green axis (negative values are greenish, positive values are reddish), b * = color value along the blue / yellow axis (negative values are bluish, positive values are yellowish)). The L * , a * and b * values were measured with a spectrophotometer DC45IR manufactured by Datacolor (measurement geometry: 45 / 0°; spectral analyzer: dual-channel holographic grating under patent rights. Referenced and used in both the reference and sample channels; light source: full bandwidth LED illumination). The following values were obtained: L * : 94.2; a * : -1.9; b * : 5.4.

[0117]

[0116] The IR reflectance spectrum of the security function obtained from the solvent-based security ink C0 was measured with a DC45IR made by Datacolor between 700 nm and 1100 nm. Using the internal standard of the device, a reflectance of 100% was measured. The obtained data are shown in Table 2B.

[0118]

[0117] The security function thus obtained appeared slightly greenish to the naked eye. Due to such a slight color tone, the solvent-based security ink C0 for thermal drying screen printing is suitable for providing a machine-readable security function that is colorless or slightly colored in the visible region and strongly absorbs in the near IR region at the same time. Despite the fact that the security function exhibits good optical properties, the ink used to prepare the security function has disadvantages that depend on organic solvents, namely, it requires complex ventilation and recirculation units, is inherently more costly, and has lower environmental friendliness.

[0119]

[0118] As described above in this specification, the solvent-based security ink C0 for thermal drying screen printing and the security function obtained therefrom are used as a comparison standard for the optical properties of the security function obtained from the aqueous security ink for thermal drying screen printing described later in this specification. The L * values measured for the security functions obtained from the inks (E1 to E17) according to the present invention and the comparative inks (C1 to C21) are the same as the L * values measured with the solvent-based security ink C0 for thermal drying screen printing, and only the a * and b * values are reported in the following table. B. Aqueous security ink for thermal drying screen printing (E1 to E17 and C1 to C21) (Preparation of the surface-treated IR absorption material Cu2PO4(OH) using various components I1 to I15)

Table 1

[0120]

[0119] 0.65 g of each component listed in Table 1, excluding I13 and I15, was added to 29.9 g of deionized water and dispersed at room temperature using a Dispermat (LC55 model) at 1000 rpm for 15 minutes. Subsequently, 12.35 g of IR absorption material was added to each solution and dispersed at room temperature at 1000 rpm for 15 minutes.

[0121]

[0120] 1.16 g of ZnSO4·7H2O(I13) was added to 29.9 g of deionized water. Subsequently, 12.35 g of IR absorption material was added, and the resulting mixture was dispersed at 1000 rpm at room temperature for 15 minutes.

[0122]

[0121] 0.32 g of Al2(SO4)3·18H2O and 0.87 g of ZnSO4·7H2O (components of I15) were added to 29.9 g of deionized water. Subsequently, 12.35 g of IR absorption material was added, and the resulting mixture was dispersed at 1000 rpm at room temperature for 15 minutes.

[0123]

[0122] The obtained solid was filtered independently and dried in an oven (HERAEUS T6060) at 60°C for 24 hours.

[0124] B1. Effects of zinc aluminum phosphate compounds (E1-E5 and C1-C11)

[0123] The security inks listed in Tables 2A-1 and 2A-2 contain the following compounds: Neoacrylic® XK-98 (DSM Neoresins): Aqueous composition containing an anionic acrylic copolymer (pH: 7.3-7.9, water content: 55-57% by weight) Ceridust (registered trademark) 3715 (Clariant): Ethylene homopolymer wax (CAS no. 9002-88-4) BYK(registered trademark)-345(BYK): Polyether-modified dimethylpolysiloxane Aerosil (registered trademark) 200 (Evonik): Hydrophilic fumed silica (CAS no. 7631-86-9) Leolate® 278 TF (Elementis): Polyurethane-based thickener (active ingredient 25% by weight (CAS not shown), 2-(2-butoxyethoxy)ethanol 20% by weight, 2,6-di-tert-butyl-p-cresol 0.5% by weight, and water 54.5% by weight) TEGO® Foamex 800 (Evonik): Emulsion of polyethersiloxane copolymer + SiO2 (CAS number unavailable) Cu2PO4(OH): As described above in this specification

[0125]

[0124] All components of the security inks listed in Tables 2A-1 and 2A-2, except for the IR absorbing material (Cu2PO4(OH) and Cu2PO4(OH) surface-treated with component Ix in Table 1), were mixed and dispersed at room temperature using a Dispermat (LC55 model) at 1000 rpm for 15 minutes.

[0126]

[0125] Next, the IR absorbing material was independently added to the already obtained composition and dispersed at 1000 rpm for 15 minutes using a Dispermat (LC55 model) at room temperature to produce 100 g of security inks E1-E5 and C1-C11.

[0127]

[0126] The pH values ​​shown in Table 2B were measured using a Metrohm 827 pH lab calibrated with buffers independently having pH 4.0, pH 7.0, and pH 9.0.

[0128]

[0127] The viscosity values ​​shown in Table 2B were measured using approximately 20 g of security ink at 25°C with a Brookfield viscometer ("RVDV-I Prime" model), with spindle 21 at 100 rpm for E1, E3, E5, C1-C6, C8-C9 and C11, and spindle 27 at 100 rpm for E2, E4, C7 and C10.

[0129]

[0128] 30g each of security inks E1-E5 and C1-C11 were placed separately in 50ml centrifuge tubes (VWR®CT 50ml) and stored in an oven (HERAEUS T6060) at 40°C for 30 days to simulate aging at room temperature for approximately 4 months. The inks were allowed to cool to room temperature before being applied to the substrates described later herein.

[0130]

[0129] The security inks listed in Tables 2A-1 and 2A-2 were individually and manually applied to trust paper strips (Louisenthal BNP paper, 100 g / m²) using a semi-automatic coater (RK Print K control coater, Model 001) equipped with bar #3 (theoretical thickness approximately 24 μm). 2 The material was applied to a 14.5cm x 17.5cm area, and then dried in a hot air dryer at approximately 50°C for about 1 minute to form a machine-readable security function in the form of a dried coating with a thickness of 6-10 μm and a size of 10cm x 13cm.

[0131]

[0130] Optical properties Δa of security functions made from security inks E1-E5 and C1-C11 * and Δb * The security function of the solvent-based security ink C0 was measured as described above in this specification.

[0132]

[0131] The colorimetric evaluation of machine-readable security features was performed using the following scale: [Table 3]

[0133]

[0132] Visual evaluation of machine-readable security features: [Table 4]

[0134]

[0133] A value less than "4" (colorimetric evaluation) is unsuitable for providing machine-readable security features that are colorless or slightly colored in the visible region and strongly absorbed in the near-IR region. [Table 5] [Table 6] [Table 7]

[0135]

[0134] As shown in Table 2B, security inks (C1) that do not contain zinc aluminum phosphate compounds have a problem with poor optical properties. In particular, the absence of one or more zinc aluminum phosphate compounds in aqueous security ink C1 results in Δa * and Δb * As shown by the values, the green color (a * (Increase in value) and yellow (b * A security function exhibited a significant shift towards an increase in value. The observed brownish color of the security function produced from aqueous security ink C1 indicated that the security ink was unsuitable for manufacturing machine-readable security functions due to the lack of a combination of a colorless or nearly colorless appearance in the visible range and strong absorbance in the near-IR range.

[0136]

[0135] In contrast to security inks that do not contain zinc aluminum phosphate compounds, the security inks (E1-E5) according to the present invention, which contain one or more of the zinc aluminum phosphate compounds in the amounts claimed herein, enable the production of machine-readable security functions having a very limited color shift compared to security functions obtained from solvent-based security ink C0. Furthermore, the presence of one or more of the zinc aluminum phosphate compounds did not have a significant effect on the IR reflectance spectra of each of the machine-readable security functions. Therefore, the security inks (E1-E5) according to the present invention are well suitable for providing machine-readable security functions that are colorless or slightly colored in the visible region and strongly absorb in the near-IR region.

[0137]

[0136] Comparative security inks C2-C11, which do not contain one or more zinc aluminum phosphate compounds in the amounts claimed herein, were used to produce machine-readable security features that had the problem of poor optical properties in the visible range.

[0138] B2. Effect of the amount of zinc aluminum phosphate compound (E6-E9 and C12-C13)

[0137] The required amount of component I3 from Table 1 was added to 29.9 g of deionized water and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). Subsequently, the required amount of the IR absorption material Cu2PO4(OH) was added and dispersed at 1000 rpm for 15 minutes at room temperature. The resulting solid was filtered independently and dried in an oven (HERAEUS T6060) at 60°C for 24 hours.

[0139]

[0138] All components of the security ink listed in Table 3A, except for the IR absorbent material, were mixed and dispersed at 1000 rpm for 15 minutes using a Dispermat (LC55 model) at room temperature. Subsequently, 13 g of the resulting solid was independently added to the composition and then dispersed at 1000 rpm for 15 minutes using a Dispermat (LC55 model) at room temperature to produce 100 g of security inks E6-E9 and C12-C13. The pH value was measured as described above in this specification. The viscosity value was measured at 25°C using a Brookfield viscometer ("RVDV-I Prime" model, spindle 21 at 100 rpm).

[0140]

[0139] 30g each of security inks E6-E9 and C12-C13 were placed separately in 50ml centrifuge tubes (VWR® CT 50ml) and stored in an oven (HERAEUS T6060) at 40°C for 30 days to simulate approximately 4 months of aging at room temperature. Before printing, the inks were allowed to cool to room temperature.

[0141]

[0140] Regarding security inks E6-E9 and C12-C13, as described above in this specification, the security inks listed in Table 3A were individually and manually applied to trust paper pieces in the form of security functions. Regarding security functions made with solvent-based security ink C0, as described above in this specification, the optical properties Δa of security functions made from security inks E6-E9 and C12-C13 were described. * and Δb * We measured it. [Table 8] [Table 9]

[0142]

[0141] As shown in Table 3B, the security inks (E6-E9) according to the present invention, comprising one or more of the zinc aluminum phosphate compounds in the amounts claimed herein, enable the production of machine-readable security functions having a very limited color shift compared to security functions obtained from solvent-based security inks C0. Furthermore, the presence of one or more of the zinc aluminum phosphate compounds did not significantly affect the IR reflectance spectra of each of the machine-readable security functions. Therefore, the security inks (E6-E9) according to the present invention are well suitable for providing machine-readable security functions that are colorless or slightly colored in the visible region and strongly absorb in the near-IR region.

[0143]

[0142] Comparative security inks C12-C13 containing one or more zinc aluminum phosphate compounds in amounts other than those requested yielded machine-readable security features that had the problem of poor optical properties in the visible range. Examples using various binders containing one or more types of acrylic resins (E10-E17 and C14-C21) The following acrylic resins are used in the security inks listed in Tables 4A-1 and 4A-2: R1: Neoacrylic (registered trademark) XK-98 (DSM): Aqueous composition containing an anionic acrylic copolymer (pH: 7.3-7.9, water content: 56% by weight) R2: Neoacrylic (registered trademark) XK-16 (DSM): Aqueous composition containing an anionic acrylic copolymer (pH: 7.5-8.2, water content: 60% by weight) R3: Neoacrylic (registered trademark) XK-237 (DSM): Aqueous composition containing an anionic acrylic copolymer (pH: 8.0-9.0, water content: 56% by weight) R4: Neoacrylic (registered trademark) BT-100 (DSM): Aqueous composition containing an anionic acrylic copolymer (pH: 1.8-2.8, water content: 60% by weight) R5: Neoacrylic (registered trademark) BT-20 (DSM): Aqueous composition containing an anionic acrylic copolymer (pH: 5.0-6.0, water content: 60% by weight) R6: Carbobond (trademark) 3005 (Lubrizol): Aqueous composition containing urethane acrylic copolymer (amount of water: 42% by weight) R7: NeoPack (trademark) E-180 (Covestro): Aqueous composition containing urethane acrylic copolymer (pH = 7.5-8.4, water content: 67% by weight) R8: Zinpol 350 (Worlee): Aqueous composition containing styrene acrylic copolymer (pH: 8-9, water content: 55% by weight) R9: Zinpol 460 (Worlee): an aqueous composition containing styrene acrylic copolymer (pH: 8.0-8.5, water content: 50% by weight).

[0144]

[0143] 0.65 g of component I3 from Table 1 was added to 29.9 g of deionized water and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). Subsequently, 12.35 g of the IR absorption material Cu2PO4(OH) was added and dispersed at 1000 rpm for 15 minutes at room temperature. The resulting solid was filtered independently and dried in an oven (HERAEUS T6060) at 60°C for 24 hours.

[0145]

[0144] All components of the security inks listed in Tables 4A-1 and 4A-2, excluding the IR absorbent material, were mixed and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). 13 g of the IR absorbent material Cu2PO4(OH) treated with component I3 was independently added to the composition and subsequently dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model) to produce 100 g of security inks E10-E17. 12 g of the IR absorbent material Cu2PO4(OH) was independently added to the composition and subsequently dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model) to produce 100 g of comparative security inks C14-C21. The pH values ​​were measured as described above in this specification. Viscosity values ​​were measured at 25°C using a Brookfield viscometer ("RVDV-I Prime" model) with spindle 21 at 100 rpm for E14, E16, E17, C18, C20, and C21, and with spindle 27 at 100 rpm for E10-E13, E15, C14-C17, and C19.

[0146]

[0145] 30g each of security inks E10-E17 and C14-C21 were placed separately in 50ml centrifuge tubes (VWR® CT 50ml) and stored in an oven (HERAEUS T6060) at 40°C for 30 days to simulate approximately 4 months of aging at room temperature. Before printing, the inks were allowed to cool to room temperature.

[0147]

[0146] Regarding security inks E10-E17 and C14-C21, as described above in this specification, the security inks listed in Tables 4A-1 and 4A-2 were independently and manually applied to trust paper pieces in the form of security functions.

[0148]

[0147] Regarding security functions made with solvent-based security ink C0, as described above in this specification, the optical properties Δa of security functions made from security inks E10-E17 and C14-C21* and Δb * We measured it. [Table 10] [Table 11] [Table 12]

[0149]

[0148] As shown in Table 4B, the security inks (E10-E17) according to the present invention, comprising various acrylic resins and one or more of the zinc aluminum phosphate compounds in the amounts claimed herein, enable the production of machine-readable security functions with very limited color shift compared to security functions obtained from solvent-based security inks C0. Furthermore, the presence of the one or more zinc aluminum phosphate compounds did not significantly affect the IR reflectance spectra of each of the machine-readable security functions. Therefore, the security inks (E10-E17) according to the present invention are well suitable for providing machine-readable security functions that are colorless or slightly colored in the visible region and strongly absorb in the near-IR region.

[0150]

[0149] Comparative security inks C14 to C21, which contain various acrylic resins but do not contain one or more zinc aluminum phosphate compounds, were used to produce machine-readable security functions that had the problem of poor optical properties in the visible range.

[0151] B4. Examples of using various methods to prepare security inks (E3, E18~E20) Method 1: The first method was the same as the method described above for Security Ink E3. Method 2: Component I3 and the IR absorbing material were thoroughly mixed in a mortar. The resulting powder was then added to acrylic resin and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). The remaining components were then added in the order shown in Table 5A (starting with deionized water) and further dispersed at 1000 rpm for 15 minutes at room temperature to produce 100 g of Security Ink E18. Method 3: Component I3 was added to the acrylic resin and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). The IR absorption compound was then added and further dispersed at 1000 rpm for 15 minutes at room temperature. The remaining components were then added in the order shown in Table 5A (starting with deionized water) and further dispersed at 1000 rpm for 15 minutes at room temperature to produce 100 g of Security Ink E20. Method 4: Component I3 was dispersed in deionized water at room temperature using a Dispermat (LC55 model) at 1000 rpm for 15 minutes. The IR absorption compound was then added and further dispersed at 1000 rpm for 15 minutes at room temperature. The dispersion was then filtered, and the resulting solid was dried in an oven at 60°C for 24 hours. The thus dried solid was then added to an acrylic resin and dispersed at 1000 rpm for 15 minutes at room temperature using a Dispermat (LC55 model). The remaining components were then added in the order shown in Table 5A (starting with deionized water) and further dispersed at 1000 rpm for 15 minutes at room temperature to produce 100 g of Security Ink E20.

[0152]

[0150] The pH value was measured as described above in this specification. The viscosity was measured at 25°C using a Brookfield viscometer ("RVDV-I Prime" model), with spindle 21 at 100 rpm for E18 and spindle 27 at 100 rpm for E19-E20.

[0153]

[0151] 30g each of security inks E18-E20 were placed separately in 50ml centrifuge tubes (VWR® CT 50ml) and stored in an oven (HERAEUS T6060) at 40°C for 30 days to simulate approximately 4 months of aging at room temperature. Before printing, the inks were allowed to cool to room temperature.

[0154]

[0152] Regarding security inks E18 to E20, the security inks described in Tables 4A-1 and 4A-2 were individually and manually applied to trust paper pieces in the form of security functions, as described above in this specification.

[0155]

[0153] Regarding security functions made with solvent-based security ink C0, the optical properties Δa of security functions made from security inks E18 to E20 are described above in this specification. * and Δb * The measurements were taken and are shown in Table 5B. [Table 13] [Table 14]

[0156]

[0154] To illustrate one possible use of the requested security ink, a machine-readable security function was prepared. Security ink E3 was manually screened on a piece of trust paper (Louisenthal BNP paper, 100 g / m²) using a 90 thread / cm screen (230 mesh) after aging at 40°C for one month. 2The ink was then applied to the surface. Subsequently, the ink was dried in a hot air dryer at a temperature of approximately 50°C for approximately 1 minute to form an IR absorption layer having a thickness of 6-10 μm and having the shape of two circular geometric patterns, as shown in Figure 1 (right). As shown in Figure 1 (left), an IR transparent layer made of blue oxide intaglio ink was manually applied as a portrait on top of the IR absorption layer, partially covering the IR absorption layer, using an Ormag® intaglio proofing press at 65°C. The second layer was dried at room temperature for 24 hours.

[0157]

[0155] Figure 1 (left) is a photograph of a machine-readable security feature taken using a phone camera under visible artificial light. The second layer, made with dried IR-transparent intaglio ink, is clearly visible, while the first layer, made with dried IR-absorbing security ink, is invisible.

[0158]

[0156] Figure 1 (right) is a photograph of a machine-readable security function taken using a near-IR camera under near-IR light. The first layer, made of dried IR-absorbing security ink, is clearly visible, while the second layer, made of dried IR-transparent intaglio ink, is almost invisible.

[0159]

[0157] According to this embodiment, a paper manufacturer could print a latent IR-absorbing layer made of the security ink according to the present invention directly onto a security substrate (such as cotton paper or BOPP) in the form of an invisible mark. Subsequently, a security printing press could apply multiple layers of security ink, which are not limited to those typically found on banknotes, by one or more printing processes.

Claims

1. A security ink for printing machine-readable security functions, having a viscosity between 50 and 3000 mPa s at 25°C and a pH between approximately 7.0 and approximately 9.

0. a) At least about 45% by weight of water, b) A binder containing one or more types of acrylic resins, present in an amount of approximately 10% to approximately 40% by weight, c) one or more IR absorbing materials in an amount of about 5 wt% to about 25 wt% in total, copper (Cu), and phosphate (PO ４ ３－ ), hydrogenophosphate (HPO ４ ２－ ), pyrophosphate (P ２ O ７ ４－ ), metaphosphate (P ３ O ９ ３－ ), fluoride, chloride, sulfate (SO ４ ２－ ), and hydroxide (OH － ), preferably one or more IR absorbing materials containing one or more anions selected from the group consisting of phosphate (PO ４ ３－ ), hydrogenophosphate (HPO ４ ２－ ), pyrophosphate (P ２ O ７ ４－ ), metaphosphate (P ３ O ９ <� ３－ ), polyphosphate, and hydroxide (OH － ), more preferably one or more anions selected from the group consisting of phosphate (PO ４ ３－ ), and hydroxide (OH － ), d) One or more zinc aluminum phosphate compounds in an amount of approximately 0.125% to approximately 5.0% by weight, wherein the ratio (R) between the amount of the one or more zinc aluminum phosphate compounds and the total amount of the one or more zinc aluminum phosphate compounds and the one or more IR absorbing materials is between approximately 2.0 and approximately 20, e) Optionally, one or more additives selected from fillers, waxes, surfactants, defoamers, thickeners, and mixtures thereof. The security ink includes, and the weight percentage is based on the total weight of the security ink.

2. The security ink according to claim 1, wherein the ratio (R) is between approximately 2.5 and approximately 20, preferably between approximately 2.5 and approximately 10.

3. At least one of the one or more IR absorbing materials is Cu ２ PO ４ The security ink according to claim 1 or 2, wherein the ink is (OH).

4. The security ink according to any one of claims 1 to 3, wherein the one or more zinc aluminum phosphate compounds independently contain about 15% to about 60% by weight of zinc, about 0.3% to about 12% by weight of aluminum, and about 5% to about 30% by weight of phosphorus, and the weight percentages are based on the total weight of the one or more zinc aluminum phosphate compounds.

5. When one or more of the aforementioned zinc aluminum phosphate compounds are calculated independently as ZnO, they are present in an amount of approximately 20% to approximately 70% by weight, and Al ２ O ３ When calculated as such, approximately 0.5% by weight to approximately 20% by weight and P ２ O ５ or PO ４ ３－ The security ink according to any one of claims 1 to 3, wherein the weight percentage, when calculated as such, contains approximately 10% to approximately 70% by weight, and the weight percentage is based on the total weight of the one or more zinc aluminum phosphate compounds.

6. The security ink according to any one of claims 1 to 5, wherein at least one of the one or more zinc aluminum phosphate compounds comprises molybdenum and / or calcium and / or strontium and / or silicon.

7. The security ink according to any one of claims 1 to 6, wherein the binder is present in an amount of about 15% to about 30% by weight, and the weight percentage is based on the total weight of the security ink.

8. The security ink according to any one of claims 1 to 7, wherein the one or more IR absorbing materials are present in a total amount of about 7% to about 15% by weight, and the weight percentage is based on the total weight of the security ink.

9. a) One or more transition elements selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, and Ni, and a phosphate (PO ４ ３－ ), hydrogenophosphate (HPO ４ ２－ ), pyrophosphate (P ２ O ７ ４－ ), metaphosphate (P ３ O ９ ３－ ), polyphosphate, silicate (SiO ４ ４－ ), condensed polysilicate; titanate (TiO ３ ２－ ), condensed polytitanate, vanadate (VO ４ ３－ ), condensed polyvanadate, molybdate (MoO ４ ２－ ), condensed molybdate, tungstate (WO ４ ２－ ), condensed polytung state, niobate (NbO ３ ２－ ), fluoride (F － ), chloride (Cl － ), sulfate (SO ４ ２－ ) and / or hydroxide (OH － Compounds comprising one or more anions selected from the group consisting of ) b) Inorganic compounds selected from the group consisting of doped tin oxide, doped indium oxide, reduced tungsten oxide, and tungsten bronze. c) Organic compounds selected from the group consisting of phthalocyanine compounds, naphthalocyanine compounds, dithiolene compounds, and lylene-based compounds, and d) those mixtures The security ink according to any one of claims 1 to 8, further comprising one or more further IR absorbing materials selected from the group consisting of the following.

10. Use of security ink according to any one of claims 1 to 9 for printing machine-readable security functions.

11. A method for generating a machine-readable security function on a substrate, comprising the steps of: a) applying a security ink according to any one of claims 1 to 9 onto a substrate, preferably by screen printing; and b) drying the security ink in the presence of air, infrared light, or a combination thereof to form the machine-readable security function on the substrate, wherein the drying step is performed after step a), and the substrate is preferably selected from the group consisting of paper, other fibrous materials, and paper-containing materials.

12. The method according to claim 11, further comprising: step c) applying an ink different from the security ink described in any one of claims 1 to 8 to the machine-readable security function obtained in step b) by a printing process selected from the group consisting of screen printing, gravure printing, intaglio printing, offset printing and combinations thereof; and step d) curing or solidifying the ink from step c) to form one or more security functions different from the machine-readable security function.

13. A machine-readable security function produced from the security ink described in any one of claims 1 to 9 by the method described in claim 11 or 12.

14. A method for authenticating security documents, a) A step of preparing a security document, preferably a banknote, made with the security ink described in any one of claims 1 to 9, and having the machine-readable security function described in claim 13; b) The step of illuminating the machine-readable security function with at least one wavelength in the IR range, c) A step of detecting the optical properties of the machine-readable security function by detecting light reflected or transmitted by the machine-readable security function at at least one wavelength, wherein one of the at least one wavelengths is in the IR range. d) A step of determining the authenticity of the security document from the optical characteristics detected by the machine-readable security function. Methods that include...

15. Step b) comprises illuminating the machine-readable security function with at least two wavelengths, where one of the at least two wavelengths is in the visible range and the other of the at least two wavelengths is in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1000 nm), The method according to claim 14, wherein step c) is to detect the optical properties of the machine-readable security function by detecting light reflected or transmitted by the machine-readable security function at at least two wavelengths, wherein one of the at least two wavelengths is in the visible range and the other one of the at least two wavelengths is in the IR range (preferably between 780 nm and 3000 nm, more preferably between 780 nm and 1600 nm, and even more preferably between 800 nm and 1200 nm).

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