UV-LED RADICAL CURABLE OFFSET PRINTING INKS AND PRINTING PROCESSES

Abstract

The present invention relates to the field of UV-LED radical-curable inks for offset printing of security documents. In particular, the invention relates to UV-LED radical-curable offset printing inks for offset printing on a security substrate or document, said UV-LED radical-curable inks having a viscosity in the range of 2.5 to 25 Pa·s at 40°C and 1000 s⁻¹ and comprising radical-curable (meth)acrylate compounds, one or more photoinitiators of Formula (I), one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds, amine-modified polyether-based acrylates, and combinations thereof, and one or more fillers and / or extenders.

Description

UV-LED RADICAL CURABLE OFFSET PRINTING INKS AND PRINTING PROCESSES FIELD OF INVENTION The present invention relates to the field of protecting security documents against counterfeiting and illegal reproduction. In particular, the present invention relates to the field of UV-LED curable offset printing inks and processes for producing features or patterns on security documents. BACKGROUND OF THE INVENTION With the constant improvement in the quality of photocopies and color printing, and in an attempt to protect security documents, such as banknotes, valuable documents or cards, transport tickets or cards, revenue stamps, and product labels, which do not have reproducible effects, against counterfeiting, forgery, or illegal reproduction, the conventional practice has been to incorporate various security features in and on these documents.Typical examples of security media include security threads, windows, fibers, planchets, sheets, decals, holograms, watermarks, security inks comprising optically variable pigments, magnetic or magnetizable thin-film interference pigments, coated interference particles, thermochromic pigments, photochromic pigments, luminescent compounds, infrared absorption compounds, ultraviolet absorption compounds, or magnetic compounds. In the technique, the application of inks to security documents is known in various printing stages, including different printing processes that use low viscosity inks, such as screen printing inks, flexographic printing inks and gravure printing inks, as well as very viscous or pasty inks, such as offset printing inks, intaglio printing inks and letterpress printing inks. Offset printing processes are indirect methods where ink is transferred from a printing plate to a blanket cylinder and then onto a substrate. Offset printing processes are either wet offset or dry offset. Wet offset processes take advantage of the difference in surface energy between the image and non-image areas of the printing plate. The image area is oleophilic, while the non-image area is hydrophilic. Therefore, the oil-based inks used in this method tend to adhere to the image area and be repelled from the non-image area of ​​the printing plate.Wet offset printing is typically carried out by applying both a dampening solution (also called a dampening solution) and an oleophilic ink to the surface of the printing plate. This allows the image areas to preferentially receive the ink, while the non-image areas preferentially receive the dampening solution. The ink deposited on the image areas is then transferred to a substrate via the impression cylinder. Dry offset processes are methods in which the blanket cylinder is coated with a metallic-coated photopolymer that forms raised areas that carry the images to be printed. pro / ηη / ζζηζ / Ε / γίΛΐ The ink adheres to the raised areas and is then transferred to the substrate via the printing cylinder. In this case, no wetting solution is required. In the field, offset printing is typically the first stage in producing printed features such as the background design of security documents. Drying offset inks involves either an oxidation process (i.e., the ink contains an oxidizing agent that reacts with oxygen in the air to produce free radicals that initiate the polymerization process of the ink matrix) or a radiation curing process, specifically UV curing (i.e., the ink contains photoinitiators that, through interaction with light, produce free radicals that initiate the polymerization of the ink matrix). Oxidation drying is a slow process, while UV curing is virtually instantaneous. Since security printing is a costly, multi-stage process requiring several intermediate drying steps, UV-curable offset printing inks are generally preferred in this field.UV-curable offset printing inks are applied as thin layers with a thickness of approximately 0.5 pm to approximately 3 pm (in the cured state) to produce features on security documents. Offset inks can be applied to both sides of the substrate (simultaneous process) to print features such as background designs on security documents, where the curing stage can be carried out simultaneously or subsequently. Typical industrial printing speeds range from approximately 8,000 sheets / hour to approximately 12,000 sheets / hour. If the ink does not dry and cure quickly and effectively, transfer occurs. Transfer happens when printing ink that is not sufficiently dry or at least partially cured adheres to the back of a printed substrate placed on top of it during the stacking of printed substrates as they come off the printing presses (see, for example, US 4604952). This poses a particular problem when printing features on security documents, especially banknotes, since such documents typically have several overlapping or partially overlapping features applied in later stages.If the previously applied feature, for example, a background image or graphic pattern, has not yet dried or cured sufficiently, not only is the entire multi-stage printing process delayed, but the resulting feature may still experience transfer or marking due to machine transfer during any subsequent printing or processing operations. During a conventional banknote printing process, offset inks are applied during one of the first stages of the overall multi-stage printing process, where offset printing is followed by other printing stages including intaglio and screen printing. If a feature or pattern is printed on a security document, such as a banknote, using an offset printing process, and that feature or pattern has poor surface curing properties, the subsequent printing stage could be delayed or ink transfer could occur.Therefore, it is essential that offset inks are completely dry or cured before starting other printing stages in order to avoid any transfer problems, particularly when the next stage is an intaglio printing stage, because the intaglio printing press applies very high pressure to the printed substrate. UV-curable inks cure via free radical mechanisms involving the activation of one or more photoinitiators capable of generating free radicals through radiation, particularly UV light. These photoinitiators then initiate polymerization, leading to the formation of a cured layer. Known free radical photoinitiators include, for example, acetophenones, benzophenones, alpha-aminoketones, alpha-hydroxyketones, phosphine oxides and phosphine oxide derivatives, and benzyldimethyl ketals. UV energy is usually provided by mercury lamps, particularly medium-pressure mercury lamps. Mercury lamps require a large amount of energy, need efficient and expensive heat dissipation systems, tend to produce ozone, and have a limited lifespan. With the aim of providing less expensive, less intervention-based, and more environmentally friendly solutions, UV-LED lamps and systems have been developed for curing inks and coatings. Unlike medium-pressure mercury lamps, which emit light in the UV-A, UV-B, and UV-C regions of the electromagnetic spectrum, UV-LED lamps emit radiation in the UV-A region. Furthermore, current UV-LED lamps emit virtually monochromatic radiation, meaning they only emit at a single wavelength, such as 365 nm, 385 nm, 395 nm, or 405 nm. The effectiveness of UV curing of a coating or ink layer depends, among other factors, on the overlap between the emission spectrum of the irradiation source used for curing and the absorption spectrum of the photoinitiator contained in the coating or ink. Consequently, UV curing of coating or ink layers containing free-radical photoinitiators conventionally used with UV-LED lamps exhibits reduced curing efficiency due to the poor overlap between the lamp's emission spectrum and the absorption spectrum of the conventionally used free-radical photoinitiators, resulting in slow or poor curing or curing defects. Photoinitiators with an absorption spectrum that roughly matches the emission wavelength of currently available UV-LED radiation sources include alpha-aminoketones, thioxanthones, ketocoumarins, bis[4-(dimethylamino)phenyl]methanone derivatives (also known as Michler ketones), and acyl phosphines. However, alpha-aminoketones and Michler ketones have recently been linked to health and / or environmental concerns. Ketocoumarins, which are also known for their high fluorescence, have low curing efficiency and are primarily experimental and / or developmental products. Acylphosphine photoinitiators are widely used in UV-LED curing due to their red-shifted absorption spectrum (peak absorption wavelength around 370 nm). They are known to exhibit low fluorescence. However, acylphosphine photoinitiators can still exhibit slow curing performance, particularly slow surface curing, and are known to be particularly sensitive to oxygen inhibition, making them less effective for curing thin layers. paci / nn / zznz / E / YiAi The thioxanthone derivatives currently in use have a maximum absorption wavelength around 370 nm and around 410 nm. However, unlike acylphosphine oxides, the thioxanthones currently in use exhibit fluorescence. As mentioned earlier in this document, UV-curable offset printing inks are used in the field of security documents, valuables, and articles against counterfeiting and illegal reproduction. These inks are applied as thin layers over security documents in the form of printed features or patterns. Luminescent security features have been widely used in the field of security documents, particularly banknotes, to provide an additional, hidden security feature. The protection of these security documents against counterfeiting and illegal reproduction is based on the concept that such features typically require specialized equipment and expertise for their detection.Luminescent security features include, for example, luminescent fibers, luminescent threads, luminescent patches, bands, or sheets (where at least a portion of such patches, bands, or sheets is luminescent), and printed luminescent features. Such printed features include luminescent numbering (printed using letterpress), printed patches (printed using indirect letterpress), and luminescent features printed using offset printing, typically at the same time and on the same printing press used to produce the security features as a background design on the security documents. Since the security documents additionally comprise, besides the offset printed features, luminescent security features, in particular, luminescent security features printed on both the same side of the offset printed feature and on the opposite side, it is required that such offset printed features do not fluoresce per se, do not fluoresce through the substrate on which they are to be applied, and do not fluoresce through contact between two printed security documents due to contamination, in order to avoid a negative impact on machine detection and / or human recognition of the luminescent security features. Therefore, there remains a need for UV-LED radical-curable offset printing inks and processes for printing features on security documents at high speed (i.e., industrial speed), with such UV-LED curable offset printing inks exhibiting good curing properties and, after curing, enabling them to produce printed features that show little or no fluorescence. BRIEF DESCRIPTION OF THE INVENTION Accordingly, an object of the present invention is to overcome the deficiencies of the prior art, as discussed above. This is achieved by providing UV-LED radical-curable offset printing inks having a viscosity in the range of approximately 2.5 to approximately 25 Pa-s at 40°C and 1000 S'1 for offset printing a feature on a substrate, said UV-LED radical-curable offset printing ink comprising: prq / ηη / ζζηζ / Ε / γίΛΐ i) from approximately 10% by weight to approximately 80% by weight of one or more radically curable (meth)acrylate compounds; ii) from approximately 4% by weight to approximately 20% by weight of one or more Formula (I) photoinitiators: (Ha) (Hb) (He) pací / ηη / ζζηζ / E / γίΛΐ where n is equal to or greater than 1, R1 are identical or different from each other and are selected from the group consisting of hydrogen and C1-C3 alkyl groups, R2 is selected from the group consisting of hydrogen and C1-C3 alkyl groups and where the sum a+b+c is between 3 and 12 and the sum d+e+f+g is between 4 and 16, iii) from about 1% by weight to about 15% by weight of one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds having a weight average molecular weight of at least 400 g / mol PS equiv., amine-modified polyether-based acrylates having a weight average molecular weight of at least 400 g / mol equiv. of PS and combinations thereof, and iv) from approximately 1% by weight to approximately 30% by weight of one or more inorganic pigments and / or one or more organic pigments, and (v) from approximately 0.5% by weight to approximately 10% by weight of one or more fillers and / or extenders, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. The UV-LED radical curable offset printing inks described herein are particularly suitable for curing by exposure to UV light, preferably at one or more wavelengths between approximately 355 nm and approximately 415 nm, using a UV-LED light source. Processes for printing one or more features onto a substrate using an offset printing process are described herein. These processes comprise the steps of applying the UV-LED radical curable offset printing ink described herein by offset printing to form an ink layer, and exposing the ink layer to UV light at a dose of at least 150 mJ / cm², preferably at least 200 mJ / cm², to cure the ink layer using a UV-LED source. Also described herein are features consisting of a cured ink layer prepared from the UV-LED radical-curable offset printing ink described herein. This document describes the uses of the features described herein for the protection of a security document, a valuable document, or an article against counterfeiting or fraud, and of security documents, valuable documents, or articles comprising one or more of the printed features described herein. Also described herein are security documents comprising the substrate described herein and the one or more printed features described herein. Also described herein are the uses of the one or more photoinitiators described herein in an amount of approximately 1% by weight to approximately 20% by weight, preferably in an amount of approximately 5% by weight to approximately 15% by weight, more preferably in an amount of approximately 8% by weight to approximately 12% by weight, and the one or more amino-containing compounds described herein in an amount of approximately 1% by weight to approximately 15% by weight, to produce a UV-LED radical-curable offset printing ink having a viscosity in the range of approximately 2.5 to approximately 25 Pa-s at 40°C and 1000 s1, said UV-LED radical curable offset printing ink being suitable for printing one or more features on a security document, said UV-LED radical curable offset printing ink comprising approximately 10 wt% to approximately 80 wt% of radically curable (meth)acrylate compounds, approximately 1 wt% to approximately 30 wt% of one or more inorganic pigments and / or one or more organic pigments and approximately 0.5 wt% to approximately 10 wt% of one or more fillers and / or extenders, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. BRIEF DESCRIPTION OF THE FIGURE Fig. 1 represents a banknote comprising a substrate (1), different security features (2-9) including an offset-printed feature, wherein said feature covers more than 70% of the total surface of the security document. DETAILED DESCRIPTION OF THE INVENTION Definitions The following definitions clarify the meaning of the terms or expressions used in the description and in the claims. As used in this document, the indefinite article "un" or "una" indicates both one or more than one and does not necessarily limit its noun of reference to the singular. As used herein, the term "approximately" means that the quantity, value, or limit in question may be the specified value designated or some other close value. In general, the term "approximately" indicating a given value is intended to denote a range within ±5% of the value. For example, the expression "approximately 100" indicates a range of 100 ± 5, i.e., the range of 95 to 105. In general, when the term "approximately" is used, it can be expected that similar results or effects according to the invention may be obtained within a range of ±5% of the stated value. However, a specified quantity, value, or limit supplemented with the term "approximately" is intended herein to also disclose the quantity, value, or limit itself, i.e., without the supplement "approximately." As used herein, the expression "and / or" means that all or only one of the elements in the group may be present. For example, the expression "A and / or B" will mean only A or only B or both A and B. In the case of only A, the term also covers the possibility that B is absent, that is, only A, but not B. As used in this document, the expression one more means one, two, three, four, etc. The expression comprising, as used herein, is intended to be non-exclusive and open-ended. Thus, for example, an ink comprising compound A may include other compounds besides A. However, the expression comprising also encompasses, as a particular realization thereof, the more restrictive meanings of consisting essentially of and prq / nn / zznz / E / YiAi consisting of, so that, for example, an ink comprising compound A may also consist (essentially) of compound A. When this description refers to preferred modes / features, combinations of these preferred modes / features will also be considered disclosed, provided that such combination of preferred modes / features is technically significant. The term UV (ultraviolet), as used herein, is intended to mean irradiation that has a wavelength component in the UV part of the electromagnetic spectrum; typically from 200 nm to 400 nm. The term security document refers to a document that is typically protected against forgery or fraud by at least one security feature. Examples of security documents include, but are not limited to, negotiable instruments and valuable commercial goods. The descriptions of specific embodiments of the present invention are presented for illustrative and descriptive purposes. They are not intended to be exhaustive, nor to limit the present invention to the precise embodiments disclosed, and obviously, many modifications and variations are possible in light of prior learning. The exemplary embodiments were chosen and described to better explain the principles of the present invention and its practical application, thereby enabling other persons skilled in the art to make better use of the present invention and various embodiments with different modifications that are suitable for the particular use contemplated. The present invention provides UV-LED radical-curable offset printing inks for producing (printing) one or more features on a security document by means of an offset printing process. The present invention further provides printed features consisting of a cured ink layer prepared from the UV-LED radical-curable offset printing ink described herein, and security documents comprising the one or more printed features described herein. The UV-LED radical-curable offset printing inks described herein are applied by means of an offset printing step, wherein said offset printing may be a wet printing process or a dry offset printing process. The one or more radically curable (meth)acrylate compounds of the UV-LED radically curable offset printing ink described herein undergo curing in the presence of the one or more photoinitiators described herein and the one or more amino-containing compounds described herein by exposure to UV light, preferably at one or more wavelengths between approximately 355 nm and approximately 415 nm, more preferably by exposure to UV light at 365 nm and / or 385 nm and / or 395 nm, emitted from a UV-LED light source. As is known to those skilled in the art, the UV-LED radically curable offset printing inks described herein could also be suitable for curing using medium-pressure mercury lamps. The UV-LED radical curable offset printing ink described herein has a viscosity in the range of approximately 2.5 to approximately 25 Pa-s at 40°C and 1000 s paq / nn / zznz / E / YiAi1; the viscosity values ​​provided herein being measured on a Haake Roto-Visco RV1 with a 2 cm cone at 0.5°, a linear speed increase from 0-1000 s1 in 30 seconds. The UV-LED radical-curable offset printing ink described herein comprises radical-curable (meth)acrylate compounds. The radical-curable (meth)acrylate compounds described herein are present in an amount of approximately 10% by weight to approximately 80.7% by weight, preferably from approximately 20.7% by weight to approximately 80.7% by weight, more preferably from approximately 30.7% by weight to approximately 80.7% by weight, and still more preferably from approximately 50.7% by weight to approximately 80.7% by weight, the weight percentages being based on the total weight of the UV-LED radical-curable offset printing ink described herein. Radical-curable compounds are cured by free radical mechanisms that involve the energy activation of one or more photoinitiators that release free radicals, which in turn initiate polymerization to form a layer or coating. The described radical-curable (meth)acrylate compounds preferably consist of one or more radical-curable (meth)acrylate oligomers and one or more radical-curable (meth)acrylate monomers. The term (meth)acrylate, in the context of the present invention, refers to both acrylate and the corresponding methacrylate. The radically curable (meth)acrylate oligomers described herein are preferably selected from the group consisting of epoxy (meth)acrylates, (meth)acrylated oils, epoxidized (meth)acrylated oils, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, polyacrylic acid (meth)acrylates, polyacrylate ester (meth)acrylates and mixtures thereof, more preferably selected from the group consisting of epoxy (meth)acrylates, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates and mixtures thereof. The radical-curable oligomers described herein are preferably (meth)acrylate oligomers, which may be branched or essentially linear, and the (meth)acrylate functional group(s) may be terminal and / or dangling side groups attached to the oligomer's main chain. Preferably, the radical-curable oligomers are selected from the group consisting of (meth)acrylate oligomers, urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether-based (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof; more preferably, they are selected from the group consisting of polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof. Suitable examples of epoxy (meth)acrylate oligomers include, without limitation, aliphatic epoxy (meth)acrylate oligomers, in particular mono(meth)acrylates, di(meth)acrylates and tri(meth)acrylates, and aromatic epoxy (meth)acrylate oligomers. Suitable examples of aromatic epoxy (meth)acrylate oligomers include bisphenol-A (meth)acrylate oligomers, such as bisphenol-A mono(meth)acrylates, bisphenol-A di(meth)acrylates and bisphenol-A tri(meth)acrylates, as well as alkoxylated bisphenol-A (meth)acrylate oligomers (such as, for example, ethoxylated and propoxylated), such as, for example, alkoxylated bisphenol-A mono(meth)acrylates, alkoxylated bisphenol-A di(meth)acrylates and alkoxylated bisphenol-A tri(meth)acrylates, where ethoxylated bisphenol-A diacrylates are particularly suitable. The radically curable (meth)acrylate monomers described herein are preferably selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, penta(meth)acrylates, hexa(meth)acrylates and mixtures thereof. Preferred examples of mono(meth)acrylates include 2(2-ethoxyethoxy)ethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, C12 / C14 alkyl (meth)acrylate, C16 / C18 alkyl (meth)acrylate, caprolactone (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, nonylphenol (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, octyldecyl (meth)acrylate, tridecyl (meth)acrylate, polyphenylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, and di(meth)acrylate. of 1,3-butylene glycol, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 3-methyl-1,5pentanediol di(meth)acrylate, alkoxylated di(meth)acrylate, esterdiol di(meth)acrylate, as well as mixtures thereof. Preferred examples of di(meth)acrylates include bisphenol A di(meth)acrylates, alkoxylated bisphenol A di(meth)acrylate (such as, for example, ethoxylated and propoxylated), bisphenol A diglycidyl ether dl(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, as well as mixtures thereof. Preferred examples of tri(meth)acrylates include trimethylolpropane tri(meth)acrylates, alkoxylated trimethylolpropane tri(meth)acrylates (such as, for example, ethoxylated and propoxylated), alkoxylated glycerol tri(meth)acrylates (such as, for example, ethoxylated and propoxylated), pentaerythritol tri(meth)acrylates, alkoxylated pentaerythritol tri(meth)acrylates, alkoxylated pentaerythritol tri(meth)acrylates (such as, for example, ethoxylated and propoxylated), as well as mixtures thereof. Preferred examples of tetra(meth)acrylates include ditrimethylolpropane tetra(meth)acrylates, pentaerythritol tetra(meth)acrylates, alkoxylated pentaerythritol tetra(meth)acrylates (such as, for example, ethoxylated and propoxylated) and mixtures thereof, preferably selected from the group consisting of ditrimethylolpropane tetra(meth)acrylates, alkoxylated pentaerythritol tetra(meth)acrylates, and mixtures thereof. For embodiments in which the UV-LED radical curable offset printing ink described herein is applied by a dry offset printing process, the UV-LED radical curable offset printing ink described herein comprising the (meth)acrylate compounds described herein may further comprise one or more vinyl ethers and / or their ethoxylated equivalents. Examples of preferred vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, ethylhexyl vinyl ether, octadecyl vinyl ether, dodecyl vinyl ether, isopropyl vinyl ether, tert-butyl vinyl ether, tert-amyl vinyl ether. ether, cyclohexyl vinyl ether, cyclohexanedimethanol monovinyl ether, cyclohexanedimethanol divinyl ether, 4-(vinyloxymethyl)cyclohexylmethyl benzoate, phenyl vinyl ether, methylphenyl vinyl ether, methoxyphenyl vinyl ether, 2-chloroethyl vinyl ether, 2-hydroxyethyl vinyl ether,4-hydroxybutyl vinyl ether, 1,6-hexanediol monovinyl ether, 3-amino-1-propanol vinyl ether, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, 4-(vinyloxy)butyl benzoate, bis[4-(vinyloxy)butyl adipate, bis[4-(vinyloxy)butyl succinate, bis[4-(vinyloxymethyl)cyclohexylmethyl glutarate, 4-(vinyloxy)butyl stearate, trimethylolpropane trivinyl ether, propylene carbonate propenyl ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, ethylene glycol butylvinyl ether, dipropylene glycol divinyl ether, triethylene glycol divinyl ether, triethylene glycol methyl vinyl ether, triethylene glycol monobutyl ether, tetraethylene glycol divinyl ether, poly(tetrahydrofuran) divinyl ether, polyethylene glycol-520 methyl vinyl ether, pluriolE200 divinyl ether, tris[4-(vinyloxy)butyl trimellitate], bis[4-(vinyloxy)butyl]1,6-hexanediyl biscarbamate, 1,4-bis(2-vinyloxyethoxy)benzene, 2,2-bis(4-vinyloxyethoxyphenyl)propane, bis[4(vinyloxy)methyl]cyclohexyl]methyl terephthalate, bis[4-(vinyloxy)methyl]cyclohexyl]methyl isophthalate], bis[4(vinyloxy)butyl](4-methyl-1,3-phenylene) biscarbamate and bis[4-vinyloxy)butyl](methylenedi-4,1-phenylene) biscarbamate. Suitable vinyl ethers are marketed by BASF under the names EVE, IBVE, DDVE, ODVE, BDDVE, DVE-2, DVE-3, CHVE, CHDM-d¡, HBVE. When present, one or more vinyl ethers and / or their ethoxylated equivalents are present in an amount of approximately 1% to approximately 5% by weight, the weight percentages being based on the total weight of the UV-LED radical-curable offset printing ink. The UV-LED radical-curable offset printing ink described herein comprises the one or more photoinitiators described herein, said one or more photoinitiators consisting of thioxanthone derivatives linked to a residue through an ester bond attached at position 2, i.e., the UV-LED radical-curable offset printing ink described herein comprises one or more photoinitiators of Formula (I): pací / nn / zznz / E / YiAi where Q has the following Formula (Ha), (IIb) or (He): (Ha) (Hb) / nn / zznz / E / YiAi (He) where n is greater than 1, R1 are identical or different from each other and are selected from the group consisting of hydrogen and C1-C3 alkyl groups (i.e., methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (nPr, n-propyl, -CH2CH2CH3), 2-propyl ( / -Pr, / so-propyl, -CH(CH3)2)), R2 are selected from the group consisting of hydrogen and C1-C3 alkyl groups (i.e., methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (nPr, n-propyl, -CH2CH2CH3), 2-propyl ( / -Pr, / so-propyl, -CH(CH3)2)) and where the sum a+b+c is between 3 and 12 and The sum d+e+f+g is between 4 and 16. The one or more photoinitiators of Formula (I) preferably have a weight-average molecular weight (MW) greater than or equal to approximately 900 g / mol of PS equivalent, wherein said weight-average molecular weights are determined by GPC (gel permeation chromatography) according to OECD test method 118, using a Malvern Viskotek GPCmax and establishing a calibration curve (log(molecular weight) = f(retention volume)) using six polystyrene standards (with molecular weights ranging from 472 to 512,000 g / mol). The device is equipped with an isocratic pump, a degasser, an autosampler, and a TDA 302 triple detector comprising a differential refractometer, a viscometer, and a dual-angle (7° and 90°) light scattering detector. For this specific measurement, only the differential refractometer is used. Two Viskotek TM4008L columns were coupled (column length, 30.0 cm, internal diameter, 8).0 mm) in series. The stationary phase was prepared from a styrene-divinylbenzene copolymer with a particle size of 6 pm and a maximum pore size of 3000 Å. During the measurements, the temperature was set at 35 °C and the samples contained 10 mg / ml of the product to be analyzed, dissolved in THF (Acros, 99.9%, anhydrous). As described in the following Examples, the samples were injected independently at a rate of 1 ml / min. The molecular weight of the compound was calculated from the chromatogram as a weight-averaged molecular weight of polystyrene equivalent (Mw PS equiv.), with a 95% confidence level and the average of three measurements of the same solution, using the following formula: Σΐ-ιΗίΜί _ ^i-1--l--1_wEFi Hi pací / ηη / ζζηζ / E / γίΛΐ where / 7, is the signal level oei aetecior a panir aei vaior casal for the retention volume V¡, M¡ is the molecular weight of the polymer fraction at the retention volume V¡yn is the number of data points. As software support, Omnisec 5.12 supplied with the device is used. According to a preferred embodiment, the UV-LED radical-curable offset printing ink described herein comprises one or more photoinitiators of Formula (I), wherein n is equal to 1, 2 or 3 and wherein Q has Formula (llb), the sum of a+b+c being between 3 and 12. According to a more preferred embodiment, the UV-LED radical-curable offset printing ink described herein comprises one or more photoinitiators of Formula (I), wherein n is equal to 1, 2 or 3 and wherein Q has Formula (llb), the sum of a+b+c being between 3 and 12 and the R1s being identical and being ethyl groups. According to a further preferred embodiment, the UV-LED radical-curable offset printing ink described herein comprises one or more photoinitiators of Formula (I), wherein n is equal to 1 (see, Formula (llb-1), 2 (see, Formula (llb-2) or 3 (see, Formula (llb-3)) and wherein Q has Formula (llb), the sum a+b+c being between 3 and 12, the R1s being identical and being ethylene groups and R2 being an ethyl group: The particularly suitable Formula (I) photoinitiators are marketed by Rahn under the name Genopol® TX-2. The one or more photoinitiators described herein are present in an amount of approximately 4% by weight to approximately 20% by weight, preferably in an amount of approximately 5% by weight to approximately 15% by weight, more preferably in an amount of approximately 8% by weight to approximately 12% by weight, the weight percentages being based on the total weight of UVLED radical curable offset printing ink. Additionally, it should be appreciated that the invention also extends to compounds in which one or more of the atoms have been substituted by an isotopic variant, such as, for example, one or more hydrogen atoms may be substituted by 2H or 3H and / or one or more carbon atoms may be substituted by 14C or 13C. The UV-LED radical-curable offset printing ink described herein comprises from approximately 1 wt% to approximately 15 wt%, preferably from approximately 2 wt% to approximately 12 wt%, of one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds having a weight-average molecular weight of at least 400 g / mol PS equivalent, amine-modified polyether-based acrylates having a weight-average molecular weight of at least 400 g / mol PS equivalent, and combinations thereof, wherein the weight-average molecular weight is measured as described herein, the weight percentages being based on the total weight of the UV-LED radical-curable offset printing ink. Such amino-containing compounds act as hydrogen donors.However, in practice, it is known that, due to their fairly high hydrophilicity, these compounds negatively affect the performance of UV-curable inks when used in wet offset processes (i.e., amines tend to make the normally oleophilic ink hydrophilic, in turn contaminating the non-image area of ​​the printing plate with this hydrophilic ink). The one or more aminobenzoate compounds described herein have a weight average molecular weight of at least 400 g / mol PS equiv., preferably at least 700 g / mol PS equiv., and more preferably at least 900 g / mol PS equiv. According to one embodiment, the one or more aminobenzoate compounds described herein comprise one or more tertiary amines, preferably one or more 4-dialkylaminobenzoate groups, most preferably one or more 4-dimethylaminobenzoate groups. The one or more aminobenzoate compounds described herein are preferably polyether-based compounds that are derivatives of alkoxylated glycerols (such as, for example, ethoxylated and propoxylated) or alkoxylated pentaerythritols (such as, for example, ethoxylated and propoxylated). Suitable examples of one or more aminobenzoate compounds have the following Formula (III): paci / nn / zznz / E / YiAi / ηη / ζζηζ / E / γίΛΐ where m is greater than 1, preferably between 1 and 4, and where the sum h+i+j+k is between 3 and 12. Particularly suitable aminobenzoate compounds are marketed by Lambson under the name SpeedCure 7040.The one or more amine-modified polyether-based acrylates described herein have a weight-average molecular weight of at least 400 g / mol PS equivalent, preferably at least 700 g / mol PS equivalent, and more preferably at least 900 g / mol PS equivalent. Preferably, the one or more amine-modified polyether-based acrylates described herein have high viscosity (such as a viscosity value greater than 500 mPas, preferably greater than 1000 mPas at 20-25 °C) and high acrylate functionality (e.g., a number of acrylate groups per molecule, in particular, an acrylate functionality greater than 2, preferably greater than 3).According to one embodiment, the one or more amine-modified polyether-based acrylates described herein are prepared by reacting a small fraction (approximately 2–15 wt%) of the acrylate double bonds of a polyether acrylate with an amine (Radiation curing, P. Glóckner, Vincentz, 2008, pp. 66–67). Such amines are preferably primary or secondary alkyl or cycloalkyl amines or aliphatic cyclic secondary amines, such as pyrrolidine, piperidine, or piperazine. Particularly suitable polyether acrylates have an acrylate functionality of at least 3. Corresponding examples include ethoxylated or propoxylated glycerol triacrylate, ethoxylated or propoxylated trimethylolpropane triacrylate, ethoxylated or propoxylated pentaerythritol tetraacrylate, and the like.Suitable amine-modified polyether-based acrylates are marketed by Allnex under the name Ebecril® 80, by Rahn under the name Genomer* 3457 and 3480, by IGM Resins under the name Photomer® 5662, and by DSM Resins under the names Neorad™ P-82 and Agisyn™ 701. The amounts of the one or more amino-containing compounds described herein (in particular, the one or more aminobenzoate compounds described herein and the one or more amine-modified polyether-based acrylates described herein) and the one or more photoinitiators of Formula (I) described herein are preferably chosen such that the molar ratio between the nitrogen of the one or more amino-containing compounds described herein (in particular, the one or more aminobenzoate compounds described herein and the one or more amine-modified polyether-based acrylates described herein) and the thioxanthone moiety of the one or more photoinitiators of Formula (I) described herein is preferably between approximately 0.1 and approximately 1, more preferably between approximately 0.2 and approximately 0.8 and even more preferably between approximately 0.4 and approximately 0.6. The preferred ranges described herein are particularly suitable for modalities where the UV-LED radical curable offset printing ink described herein is applied by a wet offset printing process. The UV-LED radical curable offset printing ink described herein further comprises the one or more inorganic pigments and / or one or more organic pigments described herein, wherein said one or more inorganic pigments and / or one or more organic pigments described herein are present in an amount of approximately 1% by weight to approximately 30% by weight, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. Typical examples of organic and inorganic pigments include, without limitation, Cl Yellow Pigment 12, Cl Yellow Pigment 42, Cl Yellow Pigment 93, CL Yellow Pigment 110, CL Yellow Pigment 147, Cl Yellow Pigment 173, CL Orange Pigment 34, CL Orange Pigment 48, CL Orange Pigment 49, Cl Orange Pigment 61, Cl Orange Pigment 71, CL Orange Pigment 73, CL Red Pigment 9, CL Red Pigment 22, CL Red Pigment 23, CL Red Pigment 67, Cl Red Pigment 122, CL Red Pigment 144, Cl Red Pigment 146, Cl Red Pigment 170, CL Red Pigment 177, CL Red Pigment 179, CL Red Pigment 185, CL Red Pigment 202, CL Red Pigment 224, CL Brown Pigment 6, CL Pigment Brown 7, CL Pigment Red 242, CL Pigment Red 254, CL Pigment Red 264, CL Pigment Brown 23, CL Pigment Blue 15, CL Pigment Blue 15:3, CL Pigment Blue 60, CL Pigment Violet 19, CL Pigment Violet 23, CL Pigment Violet 32, C.L Violet Pigment 37, CL Green Pigment 7, Cl Green Pigment 36, Cl Black Pigment 7, CL Black Pigment 11, CL White Pigment 4, Cl White Pigment 6, CL White Pigment 7, Cl White Pigment 21, Cl White Pigment 22, antimony amarillo, lead chromate, lead chromate sulphate, lead molybdate plomo, ultramarine blue, cobalt blue, manganese blue, chromium oxide green, hydrated chromium oxide green, cobalt green, cerium sulphide, cadmium sulphide, cadmium sulfoseleniuros, cinc ferrite, bismuth vanadate, Prusia blue, metallic oxides mixtos, azo, azomethine, methine, anthraquinone, phthalocyanine, perinone, perylene, dicetopyrrolopirrol, thioindigo, thiazinindigo, dioxazine, iminoisoindoline, iminoisoindolinone, quinacridona, flavantrone, indantrone, anthrapyrimidine and quinophthalone pigments.When present, the inorganic pigments, organic pigments, or mixtures thereof described herein are preferably present in an amount of approximately 0.1% by weight to approximately 45% by weight, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. According to a preferred embodiment, the one or more inorganic pigments described herein and the one or more organic pigments described herein have independently a particle size less than or equal to 5 µm, preferably less than or equal to 3 µm, when measured using a particle size meter (such as an Erichsen Model 232 grind fineness meter, scale 0-15 µm) in accordance with ISO 1524:2013. The particle size test is performed directly on the ready-to-use ink, i.e., an ink containing all the ingredients and prepared and ground as described in Examples E1-E2 and Comparative Examples C1-C4 below. The UV-LED radical curable offset printing ink described herein further comprises one or more fillers and / or extenders in an amount of approximately 0.5% to approximately 10% by weight, preferably from approximately 0.5% to approximately 5% by weight, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink.Preferably, one or more fillers and / or extenders are selected from the group consisting of carbon fibers, talcs, micas (muscovites), wollastonites, clays (calcined clays and china clays), kaolins, carbonates (e.g., calcium carbonate, sodium carbonate and aluminum carbonate), silicates (e.g., magnesium silicate, aluminum silicate), sulfates (e.g., magnesium sulfate, barium sulfate), titanates (e.g., potassium titanate), alumina hydrates, silica (including also fumed silicas), montmorillonites, graphites, anatase, rutile, bentonites, vermiculites, zinc whites, zinc sulfides, wood flours, quartz flours, natural fibers, synthetic fibers and combinations thereof.More preferably, the one or more fillers and / or extenders are selected from the group consisting of carbon fibers, talc, micas, wollastonites, clays, kaolins, carbonates, silicates, sulfates, titanates, alumina hydrates, silica, montmorillonites, graphites, bentonites, vermiculites, wood flours, quartz flours, natural fibers, synthetic fibers, and combinations thereof. Even more preferably, the one or more fillers and / or extenders are selected from the group consisting of carbonates (for example, calcium carbonate, sodium carbonate, and aluminum carbonate), silicas, talcs, clays, and mixtures thereof. The UV-LED radical-curable offset printing ink described herein may further comprise one or more waxes, preferably selected from the group consisting of synthetic waxes, petroleum waxes, and natural waxes. Preferably, the one or more waxes are selected from the group consisting of amide waxes, erucamide waxes, paraffin waxes, polyethylene waxes, polypropylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, Fischer-Tropsch waxes, silicone fluids, beeswax, candelilla wax, montana wax, carnauba wax, and mixtures thereof; more preferably, they are selected from the group consisting of paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, carnauba wax, and mixtures thereof. When present, the one or more waxes are preferably present in an amount of approximately 0.1 to approximately 5% by weight, with the weight percentages being based on the total weight of UV-LED radical curable offset printing ink. The UV-LED radical-curable offset printing ink described herein may further comprise one or more phosphine oxides as co-initiators. Suitable examples of phosphine oxides include, but are not limited to, 2,4,6-trimethylbenzoyldiphenylphosphine oxide; ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate; phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide; bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; substituted acylphosphine oxides marketed as Lambson's Speedcure XKm; and a mixture of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide. a mixture of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and 2-hydroxy-2-methylpropiophenone, a mixture of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-hydroxy-2-methylpropiophenone; and a mixture of ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate and 2-hydroxy-2-methylpropiophenone.When comprising the one or more phosphine oxides described herein, UV-LED radical curable offset printing preferably comprises from about 6% by weight to about 25% by weight, preferably from about 10% by weight to about 20% by weight of the combination of the one or more photoinitiators of Formula (I) described herein and the one or more phosphine oxides described herein, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. The UV-LED radical curable offset printing ink described herein may further comprise one or more machine-readable materials selected from the group consisting of magnetic materials, IR absorption materials, and mixtures thereof.As used herein, the term “machine-readable material” refers to a material that exhibits at least one distinctive property that is detectable by a device or machine, such as, for example, a CCD or CMOS sensor, a magnetic detector (where machine-readable materials have magnetic properties), or an IR camera (where machine-readable materials have IR absorption properties), and that may be comprised in a security feature prepared from the UV-LED radical-curable offset printing ink described herein, so as to provide a means of authenticating such security feature by the use of particular equipment for its detection and / or authentication.The one or more machine-readable materials described herein are present in an amount of approximately 1% by weight to approximately 60% by weight, preferably from approximately 5% by weight to approximately 40% by weight, the weight percentages being based on the total weight of UV-LED radical curable offset printing ink. Magnetic materials exhibit particular detectable magnetic properties of ferromagnetic or ferrimagnetic type and include permanent magnetic materials (hard magnetic materials with a coercivity He > 1000 A / m) and magnetizable materials (soft magnetic materials with a coercivity He <= 1000 A / m according to IEC60404-1 (2000)). Typical examples of magnetic materials include iron, nickel, cobalt, manganese and their magnetic alloys, carbonyl iron, chromium dioxide CrÜ2, magnetic iron oxides (e.g., Fe2O3; Fe3O4), magnetic ferrites M(ll)Fe(lIII)2θ4 and hexaferrites M(ll)Fe(lll)i2Oi9, magnetic garnets M(lll)3Fe(lll)5Oi2 (such as iron and triium garnet YaFesOip) and their products, and permanently magnetized isostructural substitution magnetic particles (e.g., CoFe2O4).In the present invention, magnetic pigment particles comprising a magnetic core material surrounded (coated) by at least one layer of another material, such as those described in WO 2010 / 115986 A2, may also be used. When present, the one or more magnetic materials are preferably present in an amount of approximately 5 to approximately 60% by weight, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink. Infrared (IR) absorption materials, that is, materials that absorb in the near-infrared (NIR) range of the electromagnetic spectrum, most commonly in the wavelength range between 700 nm and 2500 nm, are widely known and used as marking materials in security applications to give printed documents an additional, hidden security feature that aids in their authentication. For example, security features with IR absorption properties have been implemented in banknotes for use by automated money processing equipment in banking and vending applications (ATMs, vending machines, etc.) to recognize a specific banknote and verify its authenticity, particularly to distinguish it from counterfeit banknotes produced using color photocopiers.IR absorption materials include inorganic IR absorption materials, glasses comprising substantial amounts of IR absorption atoms or ions or entities that exhibit IR absorption as a cooperative effect, organic IR absorption materials, and organometallic IR absorption materials (complexes of cation(s) with organic ligand(s), wherein the individual cation and / or the individual ligand, or both together, have IR absorption properties).Typical examples of IR absorption materials include, but are not limited to, carbon black, quinone-diimonium or ammonium salts, polymethines (e.g., cyanines, squaraines, croconaines), phthalocyanine-type or naphthalocyanine (π-system IR absorption), dithiolenes, quaterrylene diimides, metal phosphates (e.g., transition metal or lanthanide phosphates), lanthanum hexaboride, indium tin oxide, tin-antimony oxide in nanoparticle form, and doped tin(IV) oxide (cooperative property of the SnO4 crystal). In the present invention, IR absorption materials comprising a compound of a transition element and whose infrared absorption is a consequence of electronic transitions within the d-shell of atoms or ions of the transition element, such as those described in WO 2007 / 060133 A2, may also be used.When present, the one or more IR-absorbing materials are preferably present in an amount of approximately 1 to approximately 40% by weight, the weight percentages being based on the total weight of UV-LED radical-curable offset printing ink. The UV-LED radical curable offset printing ink described herein may also comprise one or more markers and / or identifiers. The UV-LED radical curable offset printing ink described herein may further comprise one or more UV stabilizers for the purpose of stabilizing said ink, in particular during storage. Typical examples of suitable UV stabilizers include, without limitation, hydroquinone, hydroquinone monomethyl ether, 4-t-butylcatechol, 4-t-butylphenol, 2,6-di-t-butyl-4-methylphenol (BHT), pyrogallol, phenothiazine (PTZ), 2,4-diazabicyl(2.2.2)octane (DABCO), copper(II) salts (such as, for example, copper(II) phenoxide, copper(II) acetylacetonate, copper(II) gluconate, copper(II) tartrate, copper(II) acetate, copper(II) carbamate, copper(II) thiocarbamate, copper(II) dithiocarbamate, or copper(II) dimethyl dithiocarbamate), copper(I) salts (such as, for example, copper(II) chloride ... for example, copper(I) chloride or copper(I) acetate), tris[N-(hydroxyl-KO)-N-(nitroso-KO)benzenaminate]aluminum and mixtures thereof.When present, the one or more UV stabilizers described herein are present in the UV-LED radical curable offset printing ink in an amount of approximately 0.1% by weight to approximately 5% by weight, preferably in an amount of approximately 0.5% by weight to approximately 2% by weight, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink described herein. As those experts in the field know, the UV-LED radical curable offset printing ink described herein may also comprise one or more solvents and / or thinners. The UV-LED radical-curable offset printing ink described herein may further comprise one or more inert resins (i.e., resins that do not participate in the polymerization reaction). The inert resins may be used to adjust the viscosity of the radical-curable offset printing ink described herein, to reduce the glass transition temperature of an ink layer prepared with the radical-curable offset printing ink described herein, or to increase the adhesion of an ink layer prepared with the radical-curable offset printing ink described herein.The one or more inert resins are preferably selected from the group consisting of hydrocarbons (such as, for example, styrene-based hydrocarbon resins), acrylics (such as, for example, acrylic copolymers), styrene allyl alcohols, phenolic resins, rosin-modified resins, ketone resins, alkyd resins, and mixtures thereof. When present, the one or more inert resins described herein are present in the UV-LED wet-curable offset printing ink described herein in an amount of approximately 0.1% by weight to approximately 10% by weight, preferably in an amount of approximately 0.5% by weight to approximately 2% by weight, the weight percentages being based on the total weight of the UV-LED wet-curable offset printing ink described herein. The UV-LED curable offset printing ink described herein may further comprise additives including, but not limited to, one or more of the following components, as well as combinations thereof: co-initiators, anti-settling agents, anti-foaming agents, surfactants, and other processing aids known in the field of offset inks. The additives described herein may be present in the UV-LED wet-curable offset printing inks described herein in quantities and forms known in the art, including in the form of so-called nanomaterials, where at least one of the particle dimensions is in the range of 1 to 1000 nm. UV-LED curable offset printing inks can be applied using the offset printing processes described herein to print features on security documents at high speed. These UV-LED curable offset printing inks exhibit good curing properties and, after curing, allow the production of printed features that show little or no fluorescence. Advantageously, this allows ink manufacturers to take advantage of this low- or no-fluorescence context to produce low- or non-fluorescent inks and low- or non-fluorescent printed features. Also described herein areCompositions comprising the UV-LED radical-curable offset printing ink described herein and one or more luminescent materials. Taking advantage of the little or no fluorescence of UV-LED radical-curable offset printing inks, this allows for the formulation of compositions comprising the one or more luminescent materials described herein, wherein the luminescence characteristics of said compositions have been intentionally and freely chosen, given that no masking or interference occurs between the components of the UV-LED radical-curable offset printing ink and the incorporated luminescent materials. In other words, UV-LED radical-curable offset printing inks can be used to produce compositions and security features with targeted fluorescent properties (i.e.,fluorescent properties that are predictable and not altered by the components / ingredients of the UV-LED radical-curable offset printing ink itself). In other words, the combination in the UV-LED radical-curable offset printing inks described herein of one or more radical-curable (meth)acrylate compounds described herein, one or more Formula (I) photoinitiators described herein, one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds, amine-modified polymer-based acrylates, and combinations thereof described herein, one or more inorganic pigments and / or one or more organic pigments described herein,The one or more fillers and / or extenders and the optional additives described herein allow the production of inks with little or no fluorescence and printed features with little or no fluorescence per se, or allow the production of compositions with one or more luminescent compounds and printed security features with little or no fluorescence, with controlled and desired luminescent properties through the incorporation of the luminescent materials described herein, wherein the luminescent properties of said luminescent compounds are not substantially altered or masked by the UV-LED radical-curable offset printing inks described herein. Additionally, due to the little or no fluorescence of the UV-LED radical-curable offset printing inks, the quantity of the one or more luminescent materials described herein may be reduced.thus reducing manufacturing and production costs. Typical examples of luminescent materials include, without limitation, inorganic pigments (such as inorganic host crystals or glasses doped with luminescent ions), organic compounds, and organometallic compounds (complexes of luminescent ions with organic ligand substances). When present, the one or more luminescent materials that are inorganic pigments are preferably present in the composition comprising the UV-LED radical-curable offset printing ink described herein in an amount of approximately 1 to approximately 40% by weight, the weight percentages being based on the total weight of the composition described herein.When present, one or more proluminescent materials that are organic compounds are preferably present in the composition comprising the UV-LED radical-curable offset printing ink described herein in an amount of approximately 1 to approximately 20% by weight, the weight percentages being based on the total weight of the composition described herein. The luminescent compounds can absorb certain types of energy acting upon them and subsequently emit at least some of this absorbed energy in the form of electromagnetic radiation. The luminescent compounds are detected by exposing them to a specific wavelength of light and analyzing the emitted light.Down-conversion luminescent compounds absorb electromagnetic radiation at a higher frequency (a shorter wavelength) and re-emit it, at least partially, at a lower frequency (a longer wavelength). Up-conversion luminescent compounds absorb electromagnetic radiation at a lower frequency and re-emit it, at least partially, at a higher frequency. The light emission from luminescent materials arises from excited states in atoms or molecules. The radioactive decay of such excited states has a characteristic decay time, which depends on the material and can range from 10⁹ seconds to several hours. In the present invention, both fluorescent and phosphorescent compounds are suitable.In the case of phosphorescent compounds, the decay characteristics can also be measured and used as a machine-readable feature. Luminescent compounds in pigment form have been widely used in inks (see US 6565770, WO 2008 / 033059 A2 and WO 2008 / 092522 A1). Examples of luminescent compounds include, but are not limited to, sulfides, oxysulfides, phosphates, vanadates, etc., of non-luminescent cations, doped with at least one luminescent cation selected from the group consisting of transition metal and rare-earth ions. rare earth oxysulfides and rare earth metal complexes, such as those described in WO 2009 / 005733 A2 or in US 7108742. Examples of inorganic composite materials include, without limitation, La2O2S:Eu, ZnSiO4:Mn and YVO4:Nd. The UV-LED radical curable offset printing ink described herein is normally prepared by a method comprising a step of dispersing, mixing and / or grinding all of the ingredients described herein, namely the one or more photoinitiators of Formula (I) described herein, the one or more amino-containing compounds described herein, the one or more inorganic pigments and / or one or more organic pigments described herein, the one or more fillers and / or extenders described herein, the one or more waxes described herein, when present, and the one or more additives, when present, in the presence of the (meth)acrylate compounds described herein, thereby forming pasty compositions.The one or more photoinitiators described herein may be added to the ink during the dispersion / mixing / milling stage of all other ingredients or may be added at a later stage. In this document, we also disclose intaglio printing inks (also referred to in the art as steel die or copper plate printing inks) and letterpress printing inks comprising the ingredients described herein, in particular, comprising i) the one or more photoinitiators of Formula (I) described herein and ii) the one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds having a weight average molecular weight of at least 400 g / mol PS equiv., amine-modified polyether-based acrylates having a weight average molecular weight of at least 400 g / mol PS equiv. and combinations thereof. As described herein, the process for producing the printed feature described herein comprises Step a) applying the UV-LED radical-curable offset printing ink described herein by offset printing to form an ink layer, and b) exposing the ink layer to UV light at a dose of at least 150 mJ / cm², preferably at least 200 mJ / cm², to cure said ink layer with a UV-LED source. As described below, the dose can be measured using an EIT, Inc., USA Power Puck® II UV radiometer. The UV-LED radical curable offset printing inks described herein are applied by means of an offset printing stage, wherein such offset printing may be a wet printing process or a dry offset printing process. This document also describes processes where the UV-LED radical-curable offset printing ink described herein is applied by offset printing described herein to both sides of the substrate described herein so that ink layers are formed on both sides; that is, the same UV-LED radical-curable offset printing ink is used on both sides. This document also describes processes where two UV-LED radical-curable offset printing inks described herein are applied by offset printing described herein to both sides of the substrate described herein so that ink layers are formed on both sides; that is, two different UV-LED radical-curable offset printing inks are used on both sides. Preferably, Step b) described herein consists of exposing the ink layer to one or more wavelengths between 355 and 415 nm. Commercially available UV-LED sources typically use one or more wavelengths, such as, for example, 365 nm, 385 nm, 395 nm, and 405 nm. According to one embodiment, Step b) described herein consists of exposing the ink layer to a single wavelength between 355 and 415 nm. The process described herein is particularly suitable for producing one or more printed features on a substrate that is suitable as a substrate for a security document. The one or more printed features described herein may be continuous or discontinuous. According to one embodiment, one or more features described herein are used as background features or patterns on the security substrate or document (on one or both sides) to be subsequently printed or processed with other inks or security features. This means that, on top of the one or more features printed by the offset printing processes described herein with the UV-LED radical-curable offset printing ink described herein, additional features are printed or applied in one or more additional printing or application runs, and the one or more features printed by the offset process described herein and the additional features overlap at least partially. Fig.1 represents the front side of a security document, in particular a banknote, comprising a non-fluorescent fiduciary substrate (1), such as a cellulose-based or polymeric substrate, a background design (10) consisting of a printed feature prepared by applying and curing the UV-LED radical-curable offset printing inks described herein by means of the offset printing step described herein, and additional security features (2-9). Such security features (2-9) include, without limitation, a letter-printed serial number (2), a security thread (3), a fluorescent or phosphorescent patch (4), an intaglio printing feature (5), a transparent window (6), a numeral (7), fluorescent security fibers (8), and a printed luminescent security feature (9).The security fibers (8) are embedded in the substrate during its preparation, and the fluorescent or phosphorescent patch (4) can be applied in a separate process or printed at a later stage. The printed luminescent security element (9) can be based on the composition described herein, comprising the UV-LED radical-curable offset printing ink described herein and one or more luminescent materials described herein, and can be offset printed during the same printing stage as a background design prepared with the UV-LED radical-curable offset printing inks described herein. According to one embodiment, the one or more printed features described herein, consisting of a cured ink layer prepared from the UV-LED radically curable offset printing ink described herein, have a total surface area (i.e., the sum of the surface areas of all the one or more printed features described herein) that is greater than or equal to approximately 50%, preferably greater than or equal to approximately 60%, and even more preferably greater than or equal to approximately 70%, the percentage being based on the total surface area of ​​the substrate on which the one or more printed features are present. The one or more printed features may be applied to one or both sides of the substrate described herein.When both sides of the substrate comprise one or more of the printed features described herein, the percentages described herein, i.e., greater than or equal to approximately 50%, preferably greater than or equal to approximately 60%, even more preferably greater than or equal to approximately 70%, may be the same on both sides or may be different on both sides. Typical examples of substrates include, but are not limited to, fiber-based substrates, preferably cellulosic fiber-based substrates such as paper and paper-containing materials; polymer-based substrates; composite materials (e.g., substrates obtained by laminating layers of paper and polymer films); metals or metallized materials; glass; ceramics; and combinations thereof. Typical examples of polymer-based substrates are substrates prepared from ethylene- or propylene-based homo- and copolymers, such as polypropylene (PP) and polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). As those skilled in the art know, polymer-based substrates do not exhibit fluorescence.Typical examples of composite materials include, but are not limited to, multilayer structures (e.g., laminates) of at least one paper layer and at least one polymer film, including polymers such as those described above, as well as paper-like substrates based on blends of cellulosic and synthetic polymer fibers. In a preferred embodiment, the features are printed onto a substrate selected from offset and fiduciary papers. Offset paper is manufactured from wood pulp cellulose with properties that make the paper suitable for offset printing, including dimensional stability, curl resistance, high surface stiffness, a surface free of foreign particles, and a high level of moisture penetration resistance. Typically, the basis weight of offset paper is 30 g / m² to 250 g / m², preferably 50 g / m² to 150 g / m². Security paper (also known technically as bond paper) is manufactured from lignin-free cotton pulp. Compared to offset papers, the additional properties of security paper include enhanced mechanical strength (especially tear and abrasion resistance), soiling resistance, and treatment against degradation by microorganisms (bacteria, viruses, and fungi). The mechanical strength of security paper can be enhanced by introducing synthetic fibers into the (cotton-based) paper pulp, and soiling performance can be improved by coating or printing an anti-soiling polymer layer before printing or applying the banknote features. Biocide treatment is typically combined with anti-soiling treatment.Typically, fiduciary paper has a basis weight of between 50 and 150 g / m2, preferably between 80 and 120 g / m2. Additionally, the use of security paper instead of offset paper adds an extra layer of protection against counterfeiting, since security paper is manufactured on specialized papermaking machines available only to security paper manufacturers, and the supply chain is protected to prevent the paper from being diverted to counterfeiters. Unlike ordinary writing papers, security papers do not contain optical brighteners. These brighteners are used to give ordinary writing papers a whiter, shinier appearance, but they also exhibit strong blue fluorescence when exposed to UV light, whereas security papers remain relatively dark under similar irradiation.Papers devoid of optical brighteners are not available outside the security field, which means that bright blue fluorescence under UV light is already a sign of forgery (Optical Document Security, Third Edition, 2005, Artech House, 3.2.5, page 71). According to one embodiment, the substrate described herein is a non-fluorescent substrate, preferably a substrate based on a non-fluorescent polymer or a fiducial paper that lacks an optical brightener. The term security document refers to a document that has such value that it is potentially susceptible to attempts at falsification or illegal reproduction and that is typically protected against falsification or fraud by one or more features. Examples of security documents include, but are not limited to, negotiable instruments and valuable commercial goods. paq / nn / zznz / E / YiAi Typical examples of valuable documents include, without limitation, banknotes, deeds, notes, checks, receipts, revenue stamps and tax labels, agreements and the like, identity documents such as passports, identity cards, visas, bank cards, credit cards, transaction cards, access documents, security badges, access tickets, transport tickets or titles and the like. The term "commercially valuable merchandise" refers to packaging material, particularly for the pharmaceutical, cosmetic, electronics, or food industries, which may include one or more features designed to ensure the authenticity of the packaged contents, such as genuine pharmaceuticals. Examples of such packaging materials include, but are not limited to, labels, such as authentication mark labels, tax stamps, and tamper-evident labels and seals. The security feature described herein may also include one or more additional layers or coatings both below and above the printed feature described herein.If the adhesion between the substrate and the printed feature described herein, which consists of a cured ink layer prepared from the UV-LED radically curable offset printing ink described herein, is insufficient, for example, due to the substrate material, a surface irregularity, or a lack of surface homogeneity, an additional layer, coating, or primer may be applied between the substrate and the printed feature, as known to those skilled in the art. With the aim of further increasing the level of security and resistance against counterfeiting and illegal reproduction of security documents, the substrate may contain watermarks, security threads, fibers, planchets, luminescent compounds, windows, sheets, decals, coatings and combinations thereof. The substrate described herein, onto which the UV-LED radical curable offset printing ink described herein is applied, may consist of an intrinsic part of a security document or, alternatively, the UV-LED radical curable offset printing ink described herein is applied onto an auxiliary substrate, such as, for example, a security thread, security strip, sheet, decal or label and is accordingly transferred to a security document at a separate step. Also described herein are the uses of the one or more photoinitiators described herein to produce the UV-LED radical curable offset printing ink described herein, said UV-LED radical curable offset printing ink being suitable for printing one or more features on a security document. EXAMPLE The present invention is described in more detail below with reference to non-limiting Examples. The following Examples provide further details of the preparation of UV-LED radical-curable printing inks and the use of photoinitiators and amino-containing compounds according to the invention, along with comparative data. Photoinitiators and amino-containing compounds Table 1A / nn / zznz / E / YiAi Trade name (supplier) Structure, nTCAS and molecular weight Rest of TX / mmol / g Ρ1 OMNIPOL TX (IGM Resins) NT CAS: 813452-37-8 761 ±17 g / mol equiv. of PS 2.40 Ρ2 Genocure* ITX (Rahn) o I i Λ CX II NT CAS: 5495-84-1 254.35 (supplied by supplier) 3.91 Ρ3 Genopol® TX-2 (Rahn) C 91 oicX with n = 1-3 QU i with a+b+c = 3-12 NT CAS: no available 8 ± 12 g / mol equiv. dn 3 e PS 1.70 Ρ4 SPEEDCURE TPO-L (Lambson), 0 or _. A 'Ί° NT CAS: 84434-11-7 316.34 (provided by the supplier) pací / ηη / ζζηζ / Ε / γίΛΐ Thioxanthone residue concentration in photoinitiators P1-P3: determination by EDXRF The molar concentration of the thioxanthone moiety was determined by ED-XRF (Spectro XEPOS) using the sulfur atom signal. For each of the photoinitiators P1–P3 in Table 1A, three 50 mL solutions of 2 mg / mL of the corresponding photoinitiator in acetonitrile (Sigma-Aldrich, 99.9%) were prepared. Five-mL samples of each solution were collected, and increasing amounts of a 5 mg / mL solution of Genocure ITX (Rahn, 99.3%, according to the certificate of analysis) in acetonitrile were added. Each sample was brought up to 10 mL with acetonitrile. The resulting solutions are shown in Table 1B. Table 1B pro / ηη / ζζηζ / Ε / γίΛΐ Level P1-P3 Solution [mi] ITX Solution [mi] Acetonitrile [mi] 0 5 0 5 1 5 1 4 2 5 3 2 3 5 4 1 Each sample was independently subjected to ED-XRF measurement (Spectro XEPOS), and a spectrum was recorded. The measurement for the blank assay sample (pure acetonitrile) was derived from all spectra. For each series of samples (measurement in triplicate), the fluorescence intensity measured at 2.31 keV (Ka1 peak of S) was plotted as a function of the added ITX concentration, and a linear regression was performed. The x-intercept (abscissa at the origin) of the regression line indicated the concentration of the remaining thioxanthone present at level 0 in each sample. Average values ​​(average of three measurements) are provided in Table 1A. The corresponding average value was used to determine the thioxanthone concentration in each of the P1-P3 photoinitiators in mmol / gy to calculate the amount of P1-P3 photoinitiator to be added for the preparation of the Examples and Comparative Examples. Table 1C Trade Name (Supplier) Structure, CAS No. 2 and Molecular Weight Nitrogen / mmol / g S1 Genocure* EHA(Rahn) 2-Ethylhexyl 4-(dimethylamino)benzoate CAS No.: 21245-02-3 277.4 (provided by supplier) 3.63 S2 Ebecril® 80 (Allnex) Mixture of active agent, 30% propoxylated glycerol, esters with acrylic acid and 0.5% dipropylene glycol diacrylate CAS No.: 69.5% active ingredient (not available), 0.5% CAS No. 57472-68-1 and 30% CAS No. 52408-84-1 3983 ± 226 (g / mol PS equiv.) 1.03 S3 Speedcure 7040 (Lambson) Mixture of 1,3-di({-4-(dimethylamino)benzoylpoly[oxy(1-methylethylene)]}oxy)2,2-bis({-4-(dimethylamino)-benzoylpoly[oxy(1-methylethylene)]}oxymethyl)propane and {a4(dimethylamino)benzoylpoly(oxyethylene)-poly[oxy(1-methylethylene)]-poly(oxyethylene)}4-dimethylamino)benzoate Mixture of CAS No. 2: 1003567-84-7 and CAS No. 2: 1003557-17-2 1085 ± 20 (g / mol PS equiv.) 2.71 pro / nn / zznz / E / YiAi Nitrogen concentration of compounds containing S1-S3 amino acids: determination by potentiometric titration The molar concentration of nitrogen in the S1-S3 amino-containing compounds of Table 1C was obtained by potentiometric titration with perchloric acid. For each S1-S3 compound, three 50 mL samples were prepared at 3 mg / mL in dichloromethane (Acros, 99.99%). Five milliliters of each sample were transferred to a volumetric flask and diluted to 50 mL with dichloromethane. These solutions were titrated with a 0.01 M perchloric acid solution in glacial acetic acid, prepared by mixing 9 parts of glacial acetic acid (Sigma-Aldrich, 99%) and 1 part of a perchloric acid solution (Sigma-Aldrich, 0.1 mol / L in glacial acetic acid). The titration was performed using a Metrohm Titrando 905 equipped with a conductivity meter 826 and a Solvotrode electrode for non-aqueous solutions (LiCl saturated in ethanol). The inflection point was determined graphically. Average values ​​(in mmol / g) from three measurements are provided in Table 1C. Measurement of average molecular weight in weight The weight average molecular weight of photoinitiators P1 and P3 and of amino-containing compounds S2 and S3 was determined independently by GPC (gel permeation chromatography) according to the method described below (based on OECD test method 118): A Malvern Viskotek GPCmax was used. The device was equipped with an isocratic pump, a degasser, an autosampler, and a TDA 302 triple detector comprising a differential refractometer, a viscometer, and a dual-angle light scattering detector (7° and 90°). For this specific measurement, only the differential refractometer was used. A calibration curve (log(molecular mass) = f(retention volume)) was established using six polystyrene standards (with molecular masses ranging from 472 to 512,000 g / mol). Two Viskotek TM4008L UV-LED columns (column length, 30.0 cm; internal diameter, 8.0 mm) were coupled in series. The stationary phase was prepared from a styrene-divinylbenzene copolymer with a particle size of 6 pm and a maximum pore size of 3000 Å. During the measurement, the temperature was set at 35 °C. The analyzed samples contained 10 mg / ml of the investigated compounds dissolved in THF (Acros, 99).9%, anhydrous) and were injected at a rate of 1 ml / min. The molecular mass of the compounds was calculated from the chromatogram as average molecular weight in polystyrene equivalent weight (MW of PS equiv.), with a 95% confidence level and the average of three measurements of the same solution, using the following formula: / ηη / ζζηζ / E / γίΛΐ where H, is the detector signal level from the baseline value for the retention volume V¡, 15 M¡ is the molecular weight of the compound fraction at the retention volume 14 yn is the number of data points. As software support, the Omnisec 5.12 provided with the device was used. i nn / zznz / E / YiAi UV-LED radically curable offset printing inks comprising color pigments and printed features derived therefrom (C1-C4 and E1-E2) Table 2A Ingredients Trade Name (Supplier) Chemical Name (CAS Number) C1 C2 C3 C4 E1 E2 Ebecril® 811 Oligomer (Allnex) Polyester acrylate oligomer (active agent (CAS unknown) at 24.4% + 94108-97-1 at 75% + 1562589-5 at 0.4% + 150-76-5 at 0.2%) 35.28 36.75 37.06 41.05 33.57 36.51 Ebecril® 1606 Oligomer (Allnex) Bisphenol A epoxy diacrylate diluted with TMPTA (5581857-0 at 74.7% + 15625-89-5 at 25% + 42978-66-5 at 0.3%) 21.6 22.5 22.69 25.13 20.55 22.35 Ebecril® 150 Oligomer (Allnex) Ethoxylated bisphenol A diacrylate oligomer (CAS unknown) 10.08 10.5 10.59 11.73 9.59 10.43 Miramer M4004 Monomer Ethoxylated pentaerythritol tetraacrylate monomer (51728-26-8) 2.52 2.63 2.65 2.93 2.40 2.61 Pigments Heliogen® Blue D7088 (BASF) Pigment Blue 15:3 (147-14-8) with a particle size of 3-5 pm according to ISO1524:2013 10 10 10 10 10 10 Load Finntalc M03 (Grolman) Talc (14807-96-6 at 97% + 1318-59-8 at 1% + 16389-881 at 1% + 13717-00-5 at 1%) 0.36 0.38 0.38 0.42 0.34 0.37 Aerosil®200 Filler (Evonik) Pyrogenized silica (7631-86-9) 0.36 0.38 0.38 0.42 0.34 0.37 Florstab UV-1 Stabilizer (Kromatech) Copper(II) dimethyldithiocarbamate solution (137-29-1 at 5% + 55818-57-0 at 55% + 52408-84-1 at 40%) 1.08 1.13 1.13 1.26 1.03 1.12 S394N1 Wax (Shamrock) Polyethylene wax (8002-742) 0.36 0.38 0.38 0.42 0.34 0.37 Gelling Agent Bentone® 34 (Elementis) Organic derivative of a bentonite clay (68953-582 at 97% + 14808-60-7 at 3%) 0.36 0.38 0.38 0.42 0.34 0.37 Photoinitiator P1 8 P2 5 P3 11.5 11.5 11.5 P4 6.22 Amine Synergist S1 2.86 S2 10 10 10 S3 4 Viscosity [Pa-s] 3.91 2.92 3.63 3.27 3.69 4.11 Thioxanthone concentration / mmol / g 0.192 0.196 0.196 0.196 0.196 Amine concentration / mmol / g 0.103 0.103 0.104 0.103 0.108 Amine / thioxanthone ratio 54% 53% 53% 53% 55%. UV-LED radically curable offset printing inks comprising color pigments and luminescent pigments and printed features obtained therefrom (C5-C8 and E3-E4) Table 2B pao / ηη / ζζηζ / E / γίΛΐ Ingredients Trade Name (Supplier) Chemical Name (CAS Number) C5 C6 C7 C8 E3 E4 Ebecril® 811 Oligomer (Allnex) Polyester acrylate oligomer (active agent (CAS unknown) at 24.4% + 94108-97-1 at 75% + 15625-89-5 at 0.4% + 150-76-5 at 0.2%) 35.28 35.28 41.05 41.05 33.57 33.57 Ebecril® 1606 Oligomer (Allnex) Bisphenol A epoxy diacrylate diluted with TMPTA (55818-57-0 at 74.7% + 15625-89-5 at 25% + 42978-66-5 at 0.3%) 21.60 21.60 25.13 25.13 20.55 20.55 Ebecril® 150 Oligomer (Allnex) Ethoxylated bisphenol A diacrylate oligomer (CAS not available) 10.08 10.08 11.73 11.73 9.59 9.59 Miramer M4004 Monomer Ethoxylated pentaerythritol tetraacrylate monomer (51728-26-8) 2.52 2.52 2.93 2.93 2.40 2.40 Colored pigment Heliogen® Blue D7088 (BASF) Blue Pigment 15:3(14714-8) with a particle size of 3-5 pm according to ISO1524:2013 5 5 5 5 5 5 Luminescent pigment RADGLO VSFX02 UV GREEN (Radiant Colors) 2-(2-hydroxyphenyl)-4(3H)quinazolinone (1026-04-6) with a particle size <3 pm according to the laser diffraction method 5 5 5 LUMILUX CD GREEN 140 FS 52155 (Honeywell) ZnS:Cu (CAS not available) with a particle size of 1.5 pm according to a Coulter Lasersizer 230 5 5 5 Filler Finntalc M03 (Grolman) Talc (14807-96-6 to 97% + 1318-59-8 at 1% + 16389-88-1 at 1% + 13717-00-5 at 1%) 0.36 0.36 Aerosil® 200 Filler (Evonik) Pyrogenic Silica (7631-86-9) 0.36 0.36 Florstab UV-1 Stabilizer (Kromatech) Copper (II) Dimethyldithiocarbamate Solution (137-29-1 at 5% + 55818-57-0 at 55% + 52408-84-1 at 40%) 1.08 1.08 S394 N1 Wax (Shamrock) Polyethylene Wax (800274-2) 0.36 0.36 Gelling Agent Bentone® 34 (Elementis) Organic derivative of a bentonite clay (68953-58-2 at 97% + 14808-60-7 at 3%) 0.36 0.36 Photoinitiator P1 8 8 P3 11.5 11.5 P4 6.22 6.22 Amine Synergist S2 10 10 10 10 Viscosity [Pa-s] 4.1 3.77 3.19 2.95 3.62 3.35 Thioxanthone concentration / mmol / g 0.192 0.192 0.196 0.196 Amine concentration / mmol / g 0.103 0.103 0.103 0.103 Amine / thioxanthone ratio 54% 54% 53% 53%. The UV-LED radical-curable offset printing inks of Table 2A were prepared to assess the effectiveness of the photoinitiators P1-P4 (Table 1A) and the amine synergists S1-S3 (Table 1C) in curing the layers printed with these inks, as well as to evaluate their influence on the residual fluorescence of the printed and cured layers. The UV-LED radical-curable offset printing inks listed in Table 2B were prepared to assess the effectiveness of the photoinitiators P1, P3, and P4 (Table 1A) and the amine synergists S2 (Table 1C) in curing layers printed with these inks, and to evaluate their influence on the measured luminescence of the printed and cured layers containing either a fluorescent pigment (RADGLO VSFX02 UV GREEN) or a phosphorescent pigment (LUMILUX CD GREEN 140 FS 52155 (Honeywell)). The objective was to determine whether the residual fluorescence of the printed and cured layers due to the presence of the photoinitiator (P1, P3, and P4, Table 1A) negatively affects the luminescence signals of the luminescent pigments. The UV-LED radical curable offset printing inks of Tables 2A-B were prepared independently by mixing the ingredients listed in Tables 2A-B, except for photoinitiators P1-P4, using the SpeedMixer™ (Hauschild Engineering DAC 150 SP CM31) at room temperature. The resulting pastes were independently ground in an SDY300 three-roll mill in three passes (a first pass at a pressure of 500 kPa (5 bar), a second and a third pass at a pressure of 1,100 kPa (11 bar)). The photoinitiators P1-P4 were added independently to the pastes thus obtained and the inks thus obtained were mixed in a SpeedMixer™ (DAC 150 SP CM31 from Hauschild Engineering) at a speed of 2500 rpm for three minutes at room temperature, ground in a Loher mill (3 x 50 turns with a weight of 7.5 kg) and mixed again with the SpeedMixer™ for three minutes. The viscosity values ​​of the UV-LED radical curable offset printing inks from Tables 2A-B were independently measured at 40°C and 1000 s1 on a Haake Roto-Visco RV1 with a 2 cm cone at 0.5°, a linear speed increase from 0-1000 s1 in 30 seconds and are provided in Tables 2A-B. Curing efficacy The UV-LED radical curavie offset printing inks from Tables 2A-B were independently printed as a feature (4.5 cm x 23 cm) on a fiducial polymeric substrate (Guardian™, CCL Secure) using a Prüfbau at a pressure of 1000 N (T = 22 °C, relative humidity = 54%). The printed layers obtained were cured independently with a UV-LED-UV lamp (LUV3 at 385 nm, IST) at a dose of approximately 200 mJ / cm2. The irradiation dose was determined with the following details: The irradiation source (LUV3 at 385 nm, IST) was switched on. A Power Puck® II radiometer (EIT, Inc., USA) was placed on the conveyor belt of the irradiation apparatus designed to receive the samples to be irradiated. The Power Puck®, equipped with four filters (UVA, UVB, UVC, and UVA2), was irradiated by the irradiation source at different belt speeds. Only the dose obtained in the field was retained. UVA2. It was determined that the speed of the conveyor belt to obtain an irradiation of approximately 200 mJ / cm2 was approximately 36 m / min (average of two measured values). The printed features were cured at 36 m / min (corresponding to a dose of approximately 200 mJ / cm²) using a UV-LED-UV lamp (LUV3 at 385 nm, IST). The exact number of printed and cured layers was calculated for each sample by weighing the substrate before and after printing and curing. The weight of the printed and cured layers for all printed features was 1 g / m² ± 3%. For each sample, a curing test was performed by placing a portion of blank test sample substrate (i.e., an unprinted substrate) on the front side of the substrate bearing the printed and cured layer and subjecting the resulting assembly to a back pressure of 340 kPa (3.4 bar) at 65 °C using an ORMAG IntagIio Proof Press. The substrate bearing the printed and cured layer and the blank test sample substrate were then separated, and the optical density of the blank test sample substrate was measured to assess ink transfer. Two blank test samples were prepared to define the two possible extremes of the curing behavior.A first blank sample was obtained for testing to define the maximum effectiveness (100% curing efficiency) by measuring the optical density of an unprinted substrate sample, while the minimum effectiveness (0% curing efficiency) was defined by measuring the optical density of a sample obtained by applying back pressure to a completely uncured ink layer (without passing through the UV-LED-UV lamp) directly after printing. The maximum optical density (corresponding to a 0% curing efficiency) was defined as DOmax, while the minimum optical density (corresponding to a 100% curing efficiency) was defined as DOmin. The actual curing efficiency (curing efficiency of each sample in %) was defined as DO and calculated as follows. DOmax—DO Curing efficiency (%) = —-----—--100 j ηη / ζζηζ / Β / γίΛΐ Table 3 provides the results of the curing efficiency of the printed layer obtained with the UV-LED radically curable offset printing inks from Tables 2A-B. Table 3 Radiation dose C1 C2 C3 C4 C5 C6 C7 C8 E1 E2 E3 E4 200 mJ / cm2 93% 95% 85% 44% 86% 85% 51% 49% 95% 96% 95% 92% As shown in Table 3, the comparative offset printing ink 4, 7 and 8 (C4, C7 and C8) comprising a phosphine oxide as a photoinitiator exhibited very poor curing performance. As shown in Table 3, comparative offset printing ink 3 (C3) comprising a thioxanthone photoinitiator of Formula (I) and having a weight average molecular weight (MW) greater than 900 g / mol PS equiv., but comprising a benzoate compound as an amino-containing compound having a molecular weight less than 400 g / mol PS equiv. (in particular, a molecular weight of 277.4, supplied by the supplier), exhibited intermediate curing performance. As shown in Table 3, the comparative offset printing inks 1, 2, 5 and 6 (C1, C2, C5 and C6), i.e., the inks comprising a thioxanthone photoinitiator of a Formula (I) different from Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol PS equiv. and comprising an amino-containing compound of polyether-based acrylates compound modified as an amino-containing compound having a molecular weight greater than 400 g / mol equiv. PS (in particular, approximately 4,000 g / mol PS equivalent) showed intermediate or good curing performances, whereas offset printing inks according to the invention (E1-E4), i.e., inks comprising a thioxanthone photoinitiator of Formula (I) and having a weight average molecular weight (MW) greater than 900 g / mol PS equivalent.PS and comprising either an amino-containing compound of modified polyether-based acrylates compound as an amino-containing compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.) or a benzoate compound as an amino-containing compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 1000 g / mol PS equiv.), showed good curing performance. Fluorescence measurements The UV-LED radical-curable offset printing inks from Tables 2A-B were independently printed as a feature (4.5 cm x 23 cm) on a cotton fiduciary substrate (Louisenthal BNP paper, 100 g / m²) on a Prüfbau at 800 N. The resulting printed layers were independently cured with a UV-LED-UV lamp (LUV3 at 385 nm, IST) at a dose of 200 mJ / cm² (36 m / min). The exact amount of printed and cured layers was calculated for each sample by weighing the substrate before and after printing and curing. The weight of the printed and cured layers for all printed features was 2 g / m² ± 3%. The fluorescence of the printed and cured layers prepared with the inks in Tables 2A-B was evaluated using the method described below in this document. The results of the fluorescence tests are presented in Tables 4A-B. Fluorescence of the front side (C1-C8 and E1-E4) The residual fluorescence of the printed and cured layers was assessed using a Fluorolog II (Spex) device at 254 nm and 365 nm, using the following parameters: Detector: R928 / 0115 / 0381 Angle: 30° Position: front face Excitation slit: 2 nm (254 nm) and 1.2 nm (365 nm) Wavelength covered: 400-700 nm (1 nm increments) Detection slit: 1 nm (254 nm) and 0.6 nm (365 nm). First, the fluorescence spectrum of a portion of the blank test substrate (i.e., an unprinted substrate) was measured. Subsequently, the fluorescence spectrum of the printed and cured layers was recorded. From the resulting spectrum, the maximum fluorescence intensity was determined, the fluorescence of the blank test substrate at the same wavelength was subtracted, and the value obtained was reported with the corresponding wavelength. This corresponds to the maximum fluorescence of the front side (printed side). The luminescence of the front side of printed and cured layers prepared with the inks in Table 2B was evaluated to determine the influence of residual fluorescence from the printed and cured layer on the intrinsic luminescence intensity of the added luminescent compound. A CAMAG UV Cabinet 4 (equipped with two 8 W UV tubes at 254 nm and 366 nm) was used to observe the perceived color of the printed and cured security features with the naked eye. The measured luminescence intensity and observed color are shown in Table 4B. Fluorescence on the back side (C1-04 and E1-E2) Each of the printed and cured layers was placed against an equal-sized portion of a blank test sample substrate (i.e., an unprinted substrate), with the printed side (front side in Table 4) in contact with the blank test sample substrate. Both portions were held between two glass plates (20 cm x 15 cm x 3 mm), and this assembly was placed horizontally in an oven at 60 °C and 50% relative humidity for 72 hours. Two fluorescence measurements were then performed, as described herein: Fluorescence of the back side of the printed layer: the result (average of three measurements at three different sites on the back side) is indicated as back of the printed sample in Table 4; Fluorescence on the back side of the unprinted sample: The result (average of three measurements at three different sites on the back side) is listed as the back of the unprinted sample in Table 4 and is indicative of the transfer of fluorescent compounds from the printed layer of a sheet to the back side of the sheet placed over it. In all cases, the fluorescence spectrum of a blank test sample substrate (i.e., an unprinted substrate) was first measured, and the result was deduced from the fluorescence of the printed and cured layers. Table 4A / ηη / ζζηζ / Ε / γίΛΐ Excitation wavelength C1 C2 C3 C4 E1 E2 254 nm Front side 2.5E+06 a) (519%) 4.8E+05 (ref.) 1.7E+05 (36%) 7.5E+04 (16%) 2.0E+05 (42%) 1.6E+05 (34%) Printed sample back 1.2E+05 (13%) 9.4E+05 (ref.) 1.4E+05 (14%) 1.0E+05 (11.7°) 1.3E+05 (13.7°) 1.0E+05 (11.7°) Unprinted sample back 1.8E+05 (14%) 1.2E+06 (ref.) 1.6E+05 (13%) 1.3E+05 (10%) 1.8E+05 (15%) 1.4E+05 (12%) 365nm Front 9.6E+05 (340%) 2.8E+05 (ref.) 1.3E+05 (47%) 5.6E+04 (20%) 1.6E+05 (56%) 1.2E+05 (42%) Back of printed sample 3.6E+05 (56%) 6.5E+05 (ref.) 2.4E+05 (37%) 2.5E+05 (39%) 2.6E+05 (40%) 2.2E+05 (33%) Back of unprinted sample 4.1E+05 (49%) 8.3E+05 (ref.) 2.7E+05 (33%) 2.3E+05 (28%) 3.1E+05 (37%) 2.5E+05 (30%) Wavelength of maximum fluorescence intensity / nm b> 448 442 444 443 442 447 a) Absolute values ​​are given in photons / second; values ​​in parentheses are relative to the fluorescence intensity of Comparative Example C2 (ITX), used as a reference (ref. = 100%), b) after excitation at 365 nm. Table 4B pro / ηη / ζζηζ / Ε / γίΛΐ Excitation wavelength C5 C6 C7 C8 E3 E4 254 nm Luminescence intensity3) 4.9E+06 (100%) 5.0E+06 (100%) 1.7E+06 (35%) 4.3E+05 (9%) 1.4E+06 (29%) 3.8E+05 (8%) Perceived color Blue Blue Green Green Green Green 365 nm Luminescence intensity3' 1.2E+06 (100%) 5.8E+05 (100%) 9.4E+05 (78%) 4.7E+04 (8%) 8.5E+05 (71%) 6.9E+04 (12%) Perceived color Blue Blue Green Green Green Green a) Absolute values ​​are given in photons / second; values ​​in parentheses are relative to the luminescence intensity of Comparative Example C5 with respect to C6 (photoinitiator P1), used as references (ref. = 100%) As shown in Table 4A, the printed feature prepared with comparative offset printing ink 4 (C4) comprising a phosphine oxide as a photoinitiator showed very low fluorescence on the front and back sides. As shown in Table 4A, the printed feature prepared with comparative offset printing ink 3 (C3) comprising a thioxanthone photoinitiator of Formula (I), but comprising a benzoate compound as the amino-containing compound having a molecular weight less than 400 g / mol PS equiv. (in particular, a molecular weight of 277.4, as supplied by the supplier), exhibited low fluorescence. As shown in Table 4A, the printed feature prepared with the comparative offset printing inks 1 and 2 (C1 and C2), i.e., the inks comprising a thioxanthone photoinitiator of a Formula (I) different from Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol PS equiv. and comprising an amine-modified polyether-based acrylate compound as the amino-containing compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.), exhibited strong fluorescence on the front side, thus rendering them unsuitable. As shown in Table 4A, the printed feature prepared with comparative offset printing ink 2 (C2), i.e., the ink comprising a thioxanthone photoinitiator of a Formula (I) different from Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol equiv.PS and comprising an amine-modified polyether-based acrylate compound as an amino-containing compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.), showed strong fluorescence not only from the front and back sides of the printed feature, but also on the back side of the blank test sample substrate (unprinted substrate). As shown in Table 4A, the printed feature prepared with the offset printing inks according to the invention (E1 and E2), i.e., the inks comprising a thioxanthone photoinitiator of Formula (I) and having a weight average molecular weight (MW) greater than 900 g / mol PS equiv. and comprising either an amino-containing compound of amine-modified polyether-based acrylates compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.) or a benzoate compound as an amino-containing compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 1000 g / mol PS equiv.), exhibited low fluorescence on the front and back sides. As shown in Tables 3 and 4A, the UV-LED radical curable offset printing inks according to the present invention (E1 and E2) combined good curing performance and allowed the production of features that exhibited low fluorescence on their front and back sides, whereas the comparator inks either exhibited very poor or poor curing performance or provided features that exhibited fluorescence. As shown in Table 4B, the luminescent printed feature prepared with the comparative offset printing inks C7 and C8 (containing a phosphine oxide photoinitiator) showed a strong green luminescence signal from the added luminescent compounds (C7: fluorescent pigment; C8: phosphorescent pigment). In other words, the residual blue fluorescence of the printed and cured layer obtained from an ink containing a phosphine oxide photoinitiator did not negatively affect the signal of the added luminescent pigments. As shown in Table 4B, the luminescent printed feature prepared with the comparative offset printing inks 05 and C6 (comprising a thioxanthone having a structure different from Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol PS equiv. and comprising an amine-modified polyether-based acrylate compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.)) showed a blue luminescent signal arising essentially from the strong residual fluorescence of the printed and cured layer. In other words, the green luminescence signal from the added luminescent compounds (C5: fluorescent pigment; C6: phosphorescent pigment) was hidden by the strong residual fluorescence of the printed and cured layers, making the luminescence signal from the added luminescent compounds very difficult to detect.As shown in Table 4B, the luminescent printed feature prepared with the offset printing inks according to the invention (E3 and E4), i.e., the inks comprising a thioxanthone photoinitiator of Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol PS equiv. and comprising an amine-modified polyether-based acrylate compound having a molecular weight greater than 400 g / mol PS equiv. (in particular, about 4000 g / mol PS equiv.)) showed a strong green luminescent signal from the added luminescent compounds (E3: fluorescent pigment, E4: phosphorescent pigment). In other words, the residual blue fluorescence / ηη / ζζηζ / E / γίΛΐ of the printed and cured layers obtained from an ink comprising a thioxanthone photoinitiator having a structure according to Formula (I) and having a weight average molecular weight (MW) less than 900 g / mol of equiv.PS did not negatively affect the signal of the added luminescent pigments. As shown in Tables 3 and 4B, radically curable offset printing inks by UV-LEDs according to the present invention (E3 and E4) combined good curing performance and allowed the production of luminescent security features that showed strong luminescent signals from the added luminescent pigments (fluorescent or phosphorescent), whereas the comparator inks (C5-C8) either had poor curing performance or provided luminescent security features that showed strong residual fluorescence from the printed and cured layers, making the intrinsic luminescence signals of the added luminescent pigments very difficult to detect correctly.

Claims

CLAIMS 1. A UV-LED radical-curable offset printing ink characterized in that it has a viscosity in the range of 2.5 to 25 Pa-s at 40°C and 1000s1 for offset printing of a feature on a substrate, said UV-LED radical-curable offset printing ink comprising: i) from 10 wt% to 80 wt% of one or more radically curable (meth)acrylate compounds consisting of one or more radically curable (meth)acrylate oligomers and one or more radically curable (meth)acrylate monomers, said radically curable (meth)acrylate oligomers being selected from the group consisting of epoxy (meth)acrylates, (meth)acrylated oils, epoxidized (meth)acrylated oils, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, (meth)acrylates of polyacrylic acid, (meth)acrylates of polyacrylate esters and mixtures thereof,more preferably selected from the group consisting of epoxy (meth)acrylates, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates and mixtures thereof, and said (meth)acrylate monomers being radically curable selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, penta(meth)acrylates, hexa(meth)acrylates and mixtures thereof; i) from 4% by weight to 20% by weight of one or more photoinitiators of Formula (I): pací / ηη / ζζηζ / E / γίΛΐ where Q has the following Formula (Ha), (IIb) or (He): O (Ha) (Hb) / ηη / ζζηζ / E / γίΛΐ (IIC) where n is equal to or greater than 1, R1 are identical or different from each other and are selected from the group consisting of hydrogen and C1-C3 alkyl groups, R2 is selected from the group consisting of hydrogen and C1-C3 alkyl groups and where the sum a+b+c is between 3 and 12 and the sum d+e+f+g is between 4 and 16,iii) from 1% by weight to 15% by weight of one or more amino-containing compounds selected from the group consisting of aminobenzoate compounds having a weight average molecular weight of at least 400 g / mol PS equiv., amine-modified polyether-based acrylates having a weight average molecular weight of at least 400 g / mol PS equiv. of PS and combinations thereof, and iv) from 1% by weight to 30% by weight of one or more inorganic pigments and / or one or more organic pigments, and v) from 0.5% by weight to 10% by weight of one or more fillers and / or extenders, selected from the group consisting of carbon fibers, talcs, micas, wollastonites, clays, kaolins, carbonates, silicates, sulfates, titanates, alumina hydrates, silica, montmorillonites, graphites, bentonites, vermiculites, wood flours, quartz flours, natural fibers, synthetic fibers and combinations thereof,most preferably selected from the group consisting of carbonates, silicates, talcs, clays and mixtures thereof, the percentages by weight being based on the total weight of the UV-LED radical curable offset printing ink.

2. The UV-LED radical-curable offset printing ink according to claim 1, further characterized in that at least one of the one or more photoinitiators is of Formula (I) and wherein Q has the following Formula (llb-1), (llb-2) or (llb-3): paq / nn / zznz / E / YiAi (llb-2) (llb-3) where n equals 1, 2 or 3 and the sum a+b+c is between 3 and 12.

3. The UV-LED radical-curable offset printing ink according to any of the preceding claims, further characterized in that the one or more amino-containing compounds are selected from the group consisting of aminobenzoate compounds having a weight average molecular weight of at least 700 g / mol PS equiv., amine-modified polyether-based acrylates having a weight average molecular weight of at least 700 g / mol PS equiv., and combinations thereof.

4. The UV-LED radical-curable offset printing ink according to any of the preceding claims, further characterized in that the one or more amino-containing compounds are selected from the group consisting of aminobenzoate compounds, preferably compounds comprising 4-dialkylaminobenzoate.

5. The UV-LED radical-curable offset printing ink according to claim 4, further characterized in that the one or more amino-containing compounds are selected from the group consisting of aminobenzoate compounds having Formula (III): paq / nn / zznz / E / YiAi where m is greater than 1, preferably between 1 and 4, and where the sum h+i+j+k is between 3 and 12.

6. The UV-LED radical-curable offset printing ink according to any of the preceding claims, further characterized in that the one or more inorganic pigments and the one or more organic pigments independently have a particle size less than or equal to 5 pm, preferably less than or equal to 3 pm, when measured using a particle size meter.

7. The UV-LED radically curable offset printing ink according to any of the preceding claims, further characterized in that it additionally comprises one or more waxes preferably selected from the group consisting of paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, carnauba waxes and mixtures thereof.

8. A process for printing a feature on a substrate by means of an offset printing process characterized in that it comprises the steps of: a) applying the UV-LED radical curable offset printing ink mentioned in any one of claims 1 to 7 by means of offset printing to form an ink layer, and b) exposing the ink layer to UV light at a dose of at least 150 mJ / cm2, preferably at least 200 mJ / cm2, to cure said ink layer with a UV-LED source.

9. The process according to claim 8, further characterized in that Step b) consists of exposing the ink layer to one or more wavelengths between 355 nm and 415 nm.

10. A use of the one or more photoinitiators mentioned in claim 1 or 2 in an amount of 4 wt% to 20 wt% and the one or more amino-containing compounds described herein in an amount of 1 wt% to 15 wt% to produce a UV-LED radical-curable offset printing ink having a viscosity in the range of 2.5 to 25 Pa-s at 40°C and 1000 s1, said UV-LED radical-curable offset printing ink being suitable for printing one or more features on a security document, said UV-LED radical-curable offset printing ink comprising 10 wt% to 80 wt% of radical-curable (meth)acrylate compounds, 1 wt% to 30 wt% of one or more inorganic pigments and / or one or more organic pigments, and 0.5% to 10% by weight of one or more fillers and / or extenders, the weight percentages being based on the total weight of the UV-LED radical curable offset printing ink.

11. A printed feature consisting of a cured ink layer prepared from the UV-LED radically curable offset printing ink mentioned in any one of claims 1 to 7.

12. A security document characterized in that it comprises a substrate and one or more printed features mentioned in claim 11.

13. The security document according to claim 12, further characterized in that the one or more printed features have a total surface area greater than or equal to 50%, preferably greater than or equal to 60%, more preferably greater than or equal to 70%, the % being based on the total surface area of ​​the substrate on which said one or more printed features are present.

14. The security document according to claim 12 or 13, further characterized in that the substrate is a non-fluorescent substrate.