Cationic uv-led radiation curable protective varnish for security documents

Abstract

The present invention relates to the technical field of varnishes for protecting security documents such as banknotes from premature deleterious effects of soil and / or moisture in use and over time. In particular, the present invention provides a cationic UV-LED radiation curable protective varnish comprising: a) from about 65 wt% to about 90 wt% of a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more cationically curable monomers other than a cycloaliphatic epoxide; b) from about 1 wt% to about 10 wt% of a diaryliodonium salt; c) from about 0.01 wt% to about 5 wt% of a non-ionic surfactant; and d) a photoinitiator of general formula (I): wherein the weight percentages are based on the total weight of the cationic UV-LED curable protective varnish, and a method of coating a security document with the cationic UV-LED radiation curable protective varnish.

Description

Technical Field

[0001] This invention relates to the technical field of varnishes for protecting secure documents such as banknotes from the premature harmful effects of soil and / or moisture during use and over time. Background Technology

[0002] With the continuous improvement in the quality of color photocopies and printed materials, and the need to protect secure documents such as banknotes, valuable documents or cards, transportation tickets or cards, tax banderols, and product labels from counterfeiting, tampering, or illegal copying, the traditional practice is to introduce various security features into these documents. Typical examples of security features include security threads, windows, fibers, planchettes, foil, patches, labels, holograms, watermarks, and security features obtained from security inks containing, for example, magnetic pigments, UV-absorbing pigments, IR-absorbing pigments, optically variable pigments, polarizing pigments, luminescent pigments, conductive pigments, and surface-enhanced Raman spectroscopy particles.

[0003] As is well known, protective coatings are provided to secure documents, especially banknotes, to extend their lifespan and make them suitable for circulation. These protective coatings are applied to the document's environment and are obtained from heat- (solvent-containing) curable varnishes, radiation-curable varnishes, or combinations thereof.

[0004] European Patent Application Publication No. EP0256170A1 discloses a protective layer, essentially composed of cellulose esters or cellulose ethers, for coating banknote paper printed with ink containing 1-10% by weight of micronized wax. The protective layer is obtained by applying a solvent-containing varnish to the surface of the banknote paper by spraying, dipping, or rolling, and then curing the varnish with a stream of hot air.

[0005] Public sensitivity to environmental issues and the chemical industry's necessary response to environmental regulations have prompted the industry to develop radiation-curable protective varnishes (i.e., varnishes cured by UV-visible light radiation or electron beam radiation) that contain no or significantly reduce organic solvents (volatile organic compounds, VOCs). In addition to being more environmentally friendly than solvent-based protective varnishes, radiation-curable protective varnishes can create protective coatings with increased chemical and physical resistance and are easy to cure, thereby reducing the manufacturing time of safety documents coated with radiation-curable protective varnishes.

[0006] For example, U.S. Patent Application Publication No. US20070017647A1 describes an adaptive antifouling protective layer for extending the lifespan and circulation of secure documents. This antifouling protective layer comprises at least two coating layers: a first lower coating layer formed by a physically dried coating layer applied directly to a paper substrate to seal the pores of the paper substrate; and a second upper coating layer that protects the substrate from physical and chemical influences. US20070017647A1 specifies that, to provide the second upper coating layer with high chemical and physical resistance, a UV-curable varnish, such as a free radical crosslinking or cationic crosslinking varnish, is used. Specific examples of free radical crosslinking or cationic crosslinking UV-curable varnishes are not disclosed.

[0007] Radical UV-curable coatings suffer from insufficient adhesion, limited physical resistance, and undesirable high levels of shrinkage during curing. These coatings cure via an activated radical mechanism involving one or more radical photoinitiators that release free radicals under radiation, particularly UV light, which then initiate polymerization to form a cured layer. In contrast, cationic UV-curable coatings exhibit increased adhesion and mechanical resistance. These coatings cure via a cationic mechanism activated by UV-Vis light, involving one or more cationic photoinitiators that release cationic substances such as acids, which then initiate polymerization of monomers to form a cured adhesive.

[0008] International Patent Application Publication No. WO2014067715A1 discloses the use of a cationic UV-Vis radiation-curable protective varnish comprising a cationic curable compound and a fluorinated compound for imparting stain resistance to security documents. The cationic UV-Vis radiation-curable protective varnish described herein is applied by screen printing or flexographic printing and cured by exposure to UV light emitted by a standard mercury UV lamp.

[0009] Mercury lamps require a large amount of energy, necessitate efficient and expensive cooling systems, are prone to ozone formation, and have a limited lifespan. To provide a lower-cost, less-interventional, and more environmentally friendly solution, UV-LED-based lamps and systems have been developed for curing inks and varnishes. Unlike medium-pressure mercury lamps, which have emission bands 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 quasi-monochromatic radiation, meaning they emit only one wavelength, such as 365nm, 385nm, 395nm, or 405nm.

[0010] The UV curing efficiency of varnishes or inks depends particularly on the overlap between the emission spectrum of the radiation source used for curing and the absorption spectrum of the photoinitiator contained in the varnish or ink. Therefore, cationic UV-curable coatings or inks containing conventionally used cationic photoinitiators suffer reduced curing efficiency when cured by UV-LED lamps due to poor overlap between the emission spectrum of the UV-LED lamp and the absorption of the conventionally used photoinitiator, resulting in slow or poor curing or curing defects. Cationic UV-LED curable compositions have been described in the literature. These compositions contain a cationic photoinitiator in combination with a photosensitizer that absorbs the energy of light emitted by a UV-LED lamp and acts as a donor by transferring energy to the cationic photoinitiator. International Patent Application Publication No. WO2006093680A1 discloses a hot-melt cationic formulation that can be cured by UV-LED exposure. The cationic formulation comprises a mixture of a cationic curable monomer, propylene carbonate, 2.5 wt% of a thioxanthenium salt photosensitizer, and 2 wt% of an isopropylthioxanthenone (ITX) photosensitizer. International Patent Application Publication No. WO2007017644A1 describes a cationic inkjet ink that can be cured by exposure to a UV-LED source emitting at 395 nm. An example cationic inkjet ink comprises 36.25 wt% epoxy UVR-6105, 33.5 wt% dioxane, 11.25 wt% propylene carbonate, 3 wt% xylyl iodothium hexafluorophosphate as a photoinitiator, and 1 wt% of a sensitizer, such as isopropylthioxanthenone (ITX), 1-chloro-4-propoxy-9H-thioxanthenone (CPTX), and bis(butoxy)anthracene (DBA). WO2007017644A1 teaches that the UV-LED radiation dose required for curing ink can be significantly reduced by doubling the amounts of photoinitiator and sensitizer while maintaining a 3:1 weight ratio between the weight percentages of photoinitiator and sensitizer. Due to the photoinitiation systems used in known cationic LED-curable radiation inks in the art, particularly the amounts of sensitizers such as isopropylthioxanthone (ITX), 1-chloro-4-propoxy-9H-thioxanthone-9-one (CPTX), and bis(butoxy)anthracene (DBA) required for good curing, known cationic LED-curable radiation inks in the art exhibit high fluorescence when excited by UV light, especially when excited by UV light at wavelengths of 254 nm or 366 nm. It is well known that UV-excited luminescent security features have been widely used in the field of security documents, particularly banknotes, to impart additional covert security features to said security documents, where protecting said security documents from counterfeiting and illegal copying relies on the concept that these features typically require specialized equipment and knowledge to detect them.UV-exciteable luminescent security features include, for example, UV-exciteable luminescent fibers, UV-exciteable luminescent security lines, UV-exciteable luminescent labels, stripes, or foils (where at least a portion of the label, stripe, or foil exhibits luminescence upon UV excitation), and printed UV-exciteable luminescent features. The printed UV-exciteable luminescent features include luminescent serial numbers (printed by letterpress printing), printed labels (printed by indirect letterpress printing), and luminescent features printed by offset printing. Since security documents typically contain UV-exciteable luminescent security features covered by a protective coating obtained from a protective varnish, photoinitiation systems known in the art cannot be used in the protective varnish of security documents because the high level of fluorescence exhibited by the protective coating upon excitation with UV light at wavelengths such as 254 nm or 366 nm impairs machine detection and / or human identification of the UV-exciteable luminescent security features.

[0011] Therefore, there remains a need for a cationic UV-LED radiation-curable protective varnish for providing a protective coating for security documents at high speed (i.e., industrial speed), which extends the lifespan and circulation applicability of the security documents, wherein the cationic UV-LED radiation-curable varnish exhibits optimal curing performance and, after curing, exhibits low fluorescence in response to 254nm and 366nm excitation, which does not impair machine detection and / or human identification of the luminescent security features contained in the coated security documents that can be excited by UV light, particularly with UV light of wavelengths such as 254nm or 366nm. Summary of the Invention

[0012] Therefore, the object of the present invention is to provide a cationic UV-LED radiation-curable protective varnish for coating security documents at high speeds (i.e., industrial speeds) to extend the lifespan and circulation applicability of the security documents, wherein the cationic UV-LED radiation-curable varnish exhibits optimal curing performance and, after curing, exhibits low fluorescence in response to UV light excitation, such as 366 nm and 254 nm excitation. This is achieved by the cationic UV-LED radiation-curable protective varnish claimed herein, wherein the protective varnish comprises:

[0013] a) about 65% by weight to about 90% by weight of an alicyclic epoxide, or a mixture of an alicyclic epoxide with one or more cationic curable monomers other than the alicyclic epoxide;

[0014] b) about 1% to about 10% by weight, preferably about 2% to about 5% by weight, more preferably about 3% by weight of diaryliodomonium salt;

[0015] c) about 0.01% to about 5% by weight of nonionic surfactant; and

[0016] d) Photosensitizers of general formula (I):

[0017]

[0018] In general formula (I),

[0019] A 1 and A 2 Each is independently selected from hydrogen and the following structural components:

[0020]

[0021] -L 1 -Selected from:

[0022]

[0023] -L 2 -Selected from:

[0024]

[0025] n1 and n2 are integers greater than or equal to 0;

[0026] and

[0027] Or m represents 0;

[0028] B represents hydrogen;

[0029] C is selected from hydrogen,

[0030] A 3 and A 4 Each is independently selected from hydrogen and the following structural components:

[0031]

[0032] -L 3 -and-L 4 - Selected independently from:

[0033]

[0034] And n3 and n4 are integers greater than or equal to 0, where the sum of n1 + n2 is included between 2 and 8;

[0035] The sum of n1+n2+n3 is included between 3 and 12; and the sum of n1+n2+n3+n4 is included between 4 and 16.

[0036] or

[0037] m represents 1;

[0038] B is selected from ethyl, and

[0039] C is selected from

[0040] A 3 A 4 A 5 and A 6 Each is independently selected from hydrogen and the following structural components:

[0041]

[0042] -L 3 -、-L 4 -、-L 5 -and-L 6 - Selected independently from:

[0043]

[0044] And n3, n4, n5, and n6 are integers greater than or equal to 0, where

[0045] The sum of n1 + n2 + n3 is included in the range of 3-12;

[0046] The sum of n1+n2+n3+n4 is included in the range of 4-16;

[0047] The sum of n1+n2+n3+n4+n6 is included in the range of 5-15;

[0048] The sum of n1+n2+n3+n5 is included in the range of 4-16;

[0049] The sum of n1+n2+n3+n4+n5 is included in the range of 5-15;

[0050] The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6-18;

[0051] in

[0052] The cationic UV-LED radiation-curable protective varnish includes a portion of the photosensitizer of general formula (I). The concentration of (2-keto-thioxanthone) is about 1.3 mmol to about 4.7 mmol per 100 g of cationic UV-LED radiation curable protective varnish, preferably about 1.45 mmol to about 4.5 mmol, more preferably about 1.6 mmol to about 4.25 mmol.

[0053] The weight percentage (wt%) is based on the total weight of the cationic UV-LED radiation-curable protective varnish. Preferably, the photosensitizer contained in the cationic UV-LED radiation-curable protective varnish according to the invention is a compound of general formula (Ib).

[0054]

[0055] in

[0056] A 1 A 2 C, n1, n2, -L 1 -and-L 2 -With the meaning defined herein. More preferably, the photosensitizer contained in the cationic UV-LED radiation-curable protective varnish according to the invention is a compound of general formula (Ib), wherein C represents

[0057]

[0058] Where A 3 n3 and -L 3 - Has the meaning described in this article.

[0059] This document claims and describes a cationic UV-LED radiation-curable protective varnish that can be cured by exposure to UV light emitted by a UV-LED light source, preferably by exposure to one or more wavelengths between about 365 nm and about 405 nm, more preferably by exposure to UV light at 365 nm and / or 385 nm and / or 395 nm. Therefore, according to another aspect of the invention, there is a method for coating a security document comprising a substrate and one or more security features applied to or inserted into a portion of the substrate, wherein the method comprises the following steps:

[0060] i) Preferably, the cationic UV-LED radiation-curable protective varnish claimed and described herein is applied to the substrate surface of the security document and / or the surface of one or more security features using a printing method selected from flexographic printing, inkjet printing, and screen printing to form a varnish layer; and

[0061] ii) The varnish layer is cured by exposure to UV light emitted from a UV-LED source to form a protective coating covering the substrate surface of the security document and / or one or more security features. The coating method according to the invention is environmentally friendly and enables the convenient (i.e., industrial-speed) manufacture of antifouling protective coatings for security documents that exhibit acceptable fluorescence levels in response to UV light excitation, such as 366 nm and 254 nm excitation.

[0062] According to another aspect of the invention, there is a security document comprising a substrate, one or more security features applied to or inserted into a portion of the substrate, and a protective coating covering the substrate surface and / or the surface of one or more security features of the security document, wherein the protective coating is obtained by the coating method claimed and described herein. Detailed Implementation

[0063] definition

[0064] The following definitions are used to clarify the meaning of the terms discussed in the specification and listed in the claims.

[0065] As used in this article, the indefinite article “a / an” means one or more than one, and does not necessarily require the noun it specifies to be singular.

[0066] As used herein, the term "about" means that the quantity or value in discussion can be a specified value or some other value near it. Generally, the term "about" indicating a specific value is intended to represent a range of ±5% of that value. As an example, the phrase "about 100" represents a range of 100 ± 5, that is, a range from 95 to 105. Preferably, the range indicated by the term "about" represents a range within ±3%, more preferably ±1%, of that value. Generally, when the term "about" is used, similar results or effects according to the invention can be expected to be obtained within ±5% of the indicated value.

[0067] As used herein, the term "and / or" means that all or only one element of the group may be present. For example, "A and / or B" means "A only, or B only, or both A and B". In the case of "A only", the term also covers the possibility that B is not present, i.e., "A only, but no B".

[0068] As used herein, the term "comprising" is intended to be non-exclusive and open-ended. Thus, for example, a solution comprising compound A may include other compounds besides A. However, the term "comprising" also encompasses the more restrictive meaning of "consistently composed of" and "composed of" as in particular embodiments thereof, such that, for example, a "solution comprising A, B and optional C" may also consist (substantially) of A and B or (substantially) of A, B and C.

[0069] In cases where this specification refers to "preferred" embodiments / features, such combinations of "preferred" embodiments / features are also considered disclosed, provided that a particular combination of "preferred" embodiments / features is technically meaningful.

[0070] As used in this article, the term "one or more" refers to one, two, three, four, etc.

[0071] The terms “UV-LED radiation curable,” “UV-LED radiation curing,” “UV-LED curable,” and “UV-LED curing” refer to radiation curing via photopolymerization under the influence of one or more radiation sources emitted at wavelengths between about 365 nm and about 405 nm, such as 365 nm and / or 385 nm and / or 395 nm.

[0072] The term “cationic UV-LED radiation-curable varnish” refers to a varnish cured by a cationic mechanism activated by one or more radiation emitted from one or more UV-LED sources with wavelengths between about 365 nm and about 405 nm, such as 365 nm and / or 385 nm and / or 395 nm.

[0073] As used herein, "2-keto-thioxanthone moiety" or "2-keto-9H-thioxanthone-9-one" refers to the moiety having the following structure:

[0074]

[0075] Surprisingly, it has been found that cationic UV-LED radiation can cure protective varnishes including:

[0076] a) about 65% by weight to about 90% by weight of an alicyclic epoxide, or a mixture of an alicyclic epoxide with one or more cationic curable monomers other than the alicyclic epoxide;

[0077] b) about 1% to about 10% by weight, preferably about 2% to about 5% by weight, more preferably about 3% by weight of diaryliodomonium salt;

[0078] c) about 0.01% to about 5% by weight of nonionic surfactant; and

[0079] d) Photosensitizers of general formula (I):

[0080]

[0081] In general formula (I)

[0082] A 1 and A 2 Each is independently selected from hydrogen and the following structural components:

[0083]

[0084] -L 1 -Selected from:

[0085]

[0086] -L 2-Selected from:

[0087] n1 and n2 are integers greater than or equal to 0;

[0088] and

[0089] or

[0090] m represents 0;

[0091] B represents hydrogen;

[0092] C is selected from hydrogen,

[0093] A 3 and A 4 Each is independently selected from hydrogen and the following structural components:

[0094]

[0095] -L 3 -and-L 4 - Selected independently from:

[0096]

[0097] And n3 and n4 are integers greater than or equal to 0, where the sum of n1 + n2 is included between 2 and 8;

[0098] The sum of n1+n2+n3 is included between 3 and 12; and the sum of n1+n2+n3+n4 is included between 4 and 16.

[0099] or

[0100] m represents 1;

[0101] B is selected from ethyl, and

[0102] C is selected from

[0103] A 3 A 4 A 5 and A 6 Each is independently selected from hydrogen and the following structural components:

[0104]

[0105] -L 3 -、-L 4 -、-L 5 -and-L 6 - Selected independently from:

[0106]

[0107] And n3, n4, n5, and n6 are integers greater than or equal to 0, where

[0108] The sum of n1 + n2 + n3 is included in the range of 3-12;

[0109] The sum of n1+n2+n3+n4 is included in the range of 4-16;

[0110] The sum of n1+n2+n3+n4+n6 is included in the range of 5-15;

[0111] The sum of n1+n2+n3+n5 is included in the range of 4-16;

[0112] The sum of n1+n2+n3+n4+n5 is included in the range of 5-15;

[0113] The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6-18;

[0114] in

[0115] Cationic UV-LED radiation-curable protective varnish includes a portion of the photosensitizer present in general formula (I). The concentration of (2-keto-thioxanthone) in the portion of 1.3 mmol to 4.7 mmol, preferably 1.45 mmol to 4.5 mmol, and more preferably 1.6 mmol to 4.25 mmol per 100 g of cationic UV-LED curable protective varnish, exhibits optimal curing performance and, after curing, displays acceptable fluorescence levels in the field of secure documentation in response to UV light excitation, such as 366 nm and 254 nm excitation. A photoinitiation system using a photoinitiator of general formula (I) containing a diaryliodonium salt as a cationic photoinitiator and a photosensitizer containing one or more 2-keto-thioxanthone moieties, wherein the concentration of the 2-keto-thioxanthone moieties present in the photosensitizer of general formula (I) in the cationic UV-LED curable protective varnish is between about 1.3 mmol and about 4.7 mmol per 100 g of the cationic UV-LED curable protective varnish, preferably about 1.45 mmol and about 4.5 mmol, more preferably about 1.6 mmol and about 4.25 mmol of the 2-keto-thioxanthone moieties, ensures that the cationic UV-LED curable protective varnish exhibits optimal curing performance and provides the protective coating with a fluorescence level acceptable for the security document field in response to UV light excitation, such as 366 nm excitation and 254 nm excitation.

[0116] This document claims protection for and describes the following cationic UV-LED radiation-curable protective varnishes:

[0117] d) Photosensitizers of general formula (I):

[0118]

[0119] In general formula (I)

[0120] A 1 and A 2 Each is independently selected from hydrogen and the following structural components:

[0121]

[0122] -L 1 -Selected from:

[0123]

[0124] -L 2 -Selected from:

[0125] n1 and n2 are integers greater than or equal to 0;

[0126] and

[0127] or

[0128] m represents 0;

[0129] B represents hydrogen;

[0130] C is selected from hydrogen,

[0131] A 3 and A 4 Each is independently selected from hydrogen and the following structural components:

[0132]

[0133] -L 3 -and-L 4 - Selected independently from:

[0134]

[0135] And n3 and n4 are integers greater than or equal to 0, where the sum of n1 + n2 is included between 2 and 8;

[0136] The sum of n1+n2+n3 is included between 3 and 12; and the sum of n1+n2+n3+n4 is included between 4 and 16.

[0137] or

[0138] m represents 1;

[0139] B is selected from ethyl, and

[0140] C is selected from

[0141] A 3 A 4 A 5 and A 6 Each is independently selected from hydrogen and the following structural components:

[0142]

[0143] -L 3 -、-L 4 -、-L 5 -and-L 6 - Selected independently from:

[0144]

[0145] And n3, n4, n5 and n6 are integers greater than or equal to 0, where the sum of n1+n2+n3 is included between 3 and 12;

[0146] The sum of n1+n2+n3+n4 is included in the range of 4-16;

[0147] The sum of n1+n2+n3+n4+n6 is included in the range of 5-15;

[0148] The sum of n1+n2+n3+n5 is included in the range of 4-16;

[0149] The sum of n1+n2+n3+n4+n5 is included in the range of 5-15;

[0150] The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6-18;

[0151] And some of the photosensitizers of general formula (I) The concentration of (2-keto-thioxanthone) is about 1.3 mmol to about 4.7 mmol, preferably about 1.45 mmol to about 4.5 mmol, more preferably about 1.6 mmol to about 4.25 mmol per 100 g of cationic UV-LED radiation-curable protective varnish.

[0152] Because the cationic UV-LED radiation-curable protective varnish contains a 2-keto-thioxanthone moiety present in the photosensitizer at a concentration of about 1.3 mmol to about 4.7 mmol, preferably about 1.45 mmol to about 4.5 mmol, more preferably about 1.6 mmol to about 4.25 mmol per 100 g of the cationic UV-LED radiation-curable protective varnish, the corresponding amount of photosensitizer of general formula (I) contained in the varnish (by weight %) can be easily calculated based on the molar concentration of the 2-keto-thioxanthone moiety in the photosensitizer of general formula (I) (2-keto-thioxanthone moiety (mmol) / photosensitizer of general formula (I) (g)). The molar concentration of the 2-keto-thioxanthone moiety in the photosensitizer of general formula (I) (2-keto-thioxanthone moiety (mmol) / photosensitizer (g)) is equal to the molar concentration of sulfur in the photosensitizer of general formula (I) (sulfur (mmol) / photosensitizer (g)), which can be determined by energy-dispersive X-ray fluorescence (ED-XRF) using the signal of the sulfur atom contained in the 2-keto-thioxanthone moiety. ED-XRF measurements can be performed using an internal standard technique with a Spectro XEFOS spectrometer, employing a 9H-thioxanthone (thioxanthone) containing a compound with a known structure, such as 2-isopropyl-9H-thioxanthone (ITX), as an internal standard.

[0153] In a preferred embodiment of the invention, m represents 0 and B represents hydrogen. Therefore, a cationic UV-LED curable protective varnish comprising a photosensitizer of general formula (Ia) is preferred.

[0154]

[0155] Where A 1 A 2 C, n1, n2, -L 1 -and-L 2 - Has the meaning as defined in this article.

[0156] In an alternative preferred embodiment according to the invention, m represents 1. Therefore, the cationic UV-LED radiation-curable protective varnish claimed and described herein may contain a photosensitizer of the general formula (Id):

[0157]

[0158] Where A 1 A 2 B, C, -L 1 -、-L 2-, n1, and n2 have the meanings defined herein. A particularly preferred embodiment of the invention relates to a cationic UV-LED radiation-curable protective varnish claimed and described herein, where m represents 1 and B represents ethyl. Therefore, a cationic UV-LED radiation-curable protective varnish claimed and described herein, comprising a photosensitizer of general formula (Ib), is particularly preferred:

[0159]

[0160] Where A 1 A 2 C, n1, n2, -L 1 -and-L 2 - Has the meaning as defined in this article.

[0161] A further preferred embodiment of the invention relates to a cationic UV-LED radiation-curable protective varnish claimed and described herein, wherein m represents 1 and B represents Where -L 5 -, n5 and A 5 This has the meaning as defined herein. Therefore, cationic UV-LED radiation-curable protective varnishes claimed and described herein that contain photosensitizers of general formula (Ic) are also preferred:

[0162]

[0163] Where A 1 A 2 A 5 C, n1, n2, n5, -L 1 -、-L 2 -and-L 5 - Has the meaning as defined in this article.

[0164] Preferably, C represents Where -L 3 -, n3 and A 3 This has the meaning as defined herein. Therefore, cationic UV-LED radiation-curable protective varnishes claimed and described herein, comprising photosensitizers of general formulas (I), (Ia), (Ib), (Ic), or (Id), are preferred, where C represents... -L 3 -, n3 and A 3 With the meaning defined herein. Particularly preferred are cationic UV-LED radiation-curable protective varnishes claimed and described herein, which contain photosensitizers of general formula (Ie):

[0165]

[0166] Where A1 A 2 A 3 -L 1 -、-L 2 -、-L 3 -, n1, n2, and n3 have the meanings defined herein. Preferably, -L 1 -express And -L 2 -、-L 3 -、-L 4 -、-L 5 -and-L 6 -express Therefore, cationic UV-LED curable protective varnishes containing photosensitizers of general formulas (I), (Ia), (Ib), (Ic), (Id), or (Ie) are preferred, wherein -L 1 -express And -L 2 -、-L 3 -、-L 4 -、-L 5 -and-L 6 -express A particularly preferred embodiment of the invention relates to a cationic UV-LED curable protective varnish comprising a photosensitizer of the general formula (If):

[0167]

[0168]

[0169] Where A 1 A 2 A 3 n1, n2, and n3 have the meanings defined in this paper. In the general formula (If), A 1 A 2 and A 3 One or more, preferably two or more, representing the following 2-keto-thioxanthone moiety:

[0170]

[0171] The cationic UV-LED curable protective varnish may comprise a mixture of photosensitizers of general formulas (I), (Ia), (Ib), (Ic), (Id), (Ie), or (If), provided that the varnish contains a 2-keto-thioxanthone moiety at a concentration of about 1.3 mmol to about 4.7 mmol per 100 g of the cationic UV-LED curable protective varnish, preferably about 1.45 mmol to about 4.5 mmol, more preferably about 1.6 mmol to about 4.25 mmol. A particularly preferred cationic UV-LED curable protective varnish according to the invention comprises wherein A 1 A 2 and A 3 It is a photosensitizer of the general formula (If) of the 2-keto-thioxanthone moiety, wherein A 1 and A 2 It is the 2-keto-thioxanthone moiety and A 3 Photosensitizers representing the general formula (If) of hydrogen, and wherein A... 1 It is the 2-keto-thioxanthone moiety and A 2 and A 3 A photosensitizer of the general formula (If) representing hydrogen, characterized in that the concentration of the 2-keto-thioxanthone moiety is from about 1.3 mmol to about 4.7 mmol, preferably from about 1.45 mmol to about 1.45 mmol, more preferably from about 1.6 mmol to about 4.25 mmol per 100 g of a cationic UV-LED curable protective varnish.

[0172] In a further preferred embodiment of the invention, -L 1 -express And -L 2 -、-L 3 -、-L 4 -、-L 5 -and-L 6 -express Photosensitizers of general formulas (I), (Ia), (Ib), (Ic), (Id), (Ie), and (If) preferably have a weight-average molecular weight (M) greater than or equal to about 700 g / mol eq PS, more preferably greater than or equal to 900 g / mol eq PS. WThe weight-average molecular weight was determined by gel permeation chromatography (GPC) according to OECD (Organisation for Economic Co-operation and Development) test method 118, using Malvern Viskotek GPCmax, and a calibration curve (log(molecular weight) = f(retention volume)) was established using six polystyrene (PS) standards (molecular weight range 472 to 512000 g / mol). The apparatus was equipped with an isocratic pump, degasser, autosampler, and a triple detector TDA302, which included a differential refractometer, viscometer, and dual-angle light scattering detectors (7° and 90°). For this specific measurement, only the differential refractometer was used. Two Viskotek TM4008L columns (30.0 cm long, 8.0 mm inner diameter) were connected in series. The stationary phase consisted of particles with a diameter of 6 μm and a maximum pore size of [missing information]. The sample was prepared from a styrene-divinylbenzene copolymer. During the measurements, the temperature was fixed at 35°C, and the sample contained 10 mg / mL of the analyte dissolved in THF (Acros, 99.9%, anhydrous). As described in the examples below, the sample was injected independently at a rate of 1 mL / min. The molecular weight of the compound was calculated from the chromatogram as the polystyrene equivalent weight-average molecular weight (PS eq MW) using the following formula, with a 95% confidence level and the average of three measurements of the same solution:

[0173]

[0174] Where H i It is the distance to the preserved volume V i The baseline detector signal level, M i In the retention volume V i The molecular weight of the polymer fraction at the given location is given, and n is the number of data points. Omnisec 5.12, included with the device, is used as the software.

[0175] Preferably, the concentration of the 2-keto-thioxanthone moiety in the cationic UV-LED curable protective varnish is about 1.3 mmol to about 4.7 mmol per 100 g of the cationic UV-LED curable protective varnish, preferably about 1.45 mmol to about 4.5 mmol, more preferably about 1.6 mmol to about 4.25 mmol, and particularly preferably about 1.6 mmol to about 2.9 mmol, for example, about 1.63 mmol to about 2.9 mmol of the 2-keto-thioxanthone moiety. The cationic UV-LED curable protective varnishes claimed and described herein include:

[0176] b) about 1% to about 10% by weight, preferably about 2% to about 5% by weight, more preferably about 3% by weight of diaryliodomonium salt.

[0177] As used herein, the term "diaryliodonium salt" refers to a cationic photoinitiator comprising diaryliodonium as a cationic moiety and any suitable anionic moiety, said anionic moiety including but not limited to BF4. - (Tetrafluoroborate, CASNr 14874-70-5), B(C6F5)4 - (Tetra(pentafluorophenyl)borate, CAS Nr47855-94-7), PF6 - (Hexafluorophosphate, CAS Nr 16919-18-9), AsF6 - (Hexafluoroarsenate, CAS Nr 16973-45-8), SbF6 - (Hexafluoroantimonate, CAS Nr17111-95-4), CF3SO3 - (trifluoromethanesulfonate, CAS Nr 37181-39-8), (CH3C6H4)SO3 - (4-Methylbenzenesulfonate, CAS Nr16722-51-3), (C4F9)SO3 - (1,1,2,2,3,3,4,4,4-nonafluoro-1-butanesulfonate, CASNr45187-15-3), (CF3)CO2 - (Trifluoroacetate, CAS Nr 14477-72-6), (C4F9)CO2 - (2,2,3,3,4,4,5,5,5-nonafluoro-1-pentanoate, CAS Nr 45167-47-3), and (CF3SO2)3C - (Tris(trifluoromethylsulfonyl)methyl compound, CAS Nr 130447-45-9).

[0178] The two aryl groups of the diaryliodonium cationic moiety can be independently substituted by one or more straight-chain or branched alkyl groups, said straight-chain or branched alkyl groups (e.g., methyl, ethyl, isopropyl, isobutyl, tert-butyl, undecyl, dodecyl, tridecyl, tetradecyl, etc.) optionally substituted by one or more halogens and / or one or more hydroxyl groups; substituted by one or more alkoxy groups, said alkoxy groups optionally substituted by one or more halogens and / or one or more hydroxyl groups; substituted by one or more nitro groups; substituted by one or more halogens; substituted by one or more hydroxyl groups; or substituted by combinations thereof. Examples of the diaryl iodine cationic moieties described herein include bis(4-dodecylphenyl)iodine (CAS Nr71786-69-1), bis[4-(1,1-dimethylethyl)phenyl]iodine (CAS Nr 61267-44-5), (4-isopropylphenyl)(4-methylphenyl)iodine (CAS Nr 178233-71-1), bis(4-methylphenyl)iodine (CAS Nr46449-56-3), (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodine (CAS Nr 344562-79-4), bis(2,4-dimethylphenyl)]iodine (CAS Nr78337-07-2), and bis(3,4-dimethylphenyl)]iodine (CAS Nr 61267-44-5), bis(4-isopropylphenyl)(4-methylphenyl)iodine (CAS Nr 78337-07-2), bis(3,4-dimethylphenyl)] ...4-dimethylphenyl)]iodine (CAS Nr 78337-07-2), bis(4-dimethylphenyl)]iodine (CAS Nr 78337-07-2), bis(4-dimethylphenyl)]iodine (CAS Nr 78337-44-54-54-54-54-54-54-55-54-55-55-55-55-55-55-55-55-55-55-55-55-55 66482-57-3), (4-methylphenyl)(2,4,6-trimethylphenyl)iodonium (CAS Nr 758629-51-5), bis[(4-(2-methylpropyl)phenyl]iodonium (CAS Nr 157552-66-4), bis(4-butylphenyl)iodonium (CAS Nr 76310-29-7), bis(2,4,6-Trimethylphenyl)iodonium (CAS Nr94564-97-3), bis(4-hexylphenyl)iodonium (CAS Nr 249300-48-9), bis(4-decylphenyl)iodonium (CAS Nr137141-44-7), (4-decylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-83-3), bis(4-undecylphenyl)iodonium (CAS Nr 167997-61-7), bis(4-tridecylphenyl)iodonium (CAS Nr 124053-08-3), bis(4-tetradecylphenyl)iodonium (CAS Nr 167997-63-9), bis(4-hexadecylphenyl)iodonium (CAS Nr137141-41-4), bis(4-heptadecylphenyl)iodonium (CAS Nr 137141-41-4), bis(4-heptadecylphenyl)iodonium (CAS Nr 124053-08-3), bis(4-tetradecylphenyl)iodonium (CAS Nr 167997-63-9), bis(4-hexadecylphenyl)iodonium (CAS Nr 137141-41-4), bis(4-hepta ... CAS Nr 202068-75-5, (4-decylphenyl)(4-dodecylphenyl)iodonium (CAS Nr 167997-67-3), (4-decylphenyl)(4-tridecylphenyl)iodonium (CAS Nr 167997-77-5), (4-decylphenyl)(4-tetradecylphenyl)iodonium (CAS Nr 167997-81-1), (4-dodecylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-71-9), (4-dodecylphenyl)(4-tridecylphenyl)iodonium (CAS Nr 167997-69-5), (4-dodecylphenyl)(4-tetradecylphenyl)iodonium (CAS Nr 202068-75-5), 167997-65-1), (4-tetraylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-73-1), (4-tetradecylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-79-7), (4-tetradecylphenyl)(4-tetraylphenyl)iodonium (CAS Nr 167997-75-3), p-(octoxyphenyl)phenyliodonium (CAS Nr 121239-74-5), [4-[(2-hydroxytetradecyl)oxy]phenyl]phenyliodonium (CAS Nr 139301-14-7), phenyl[3-(trifluoromethyl)phenyl]iodonium (CAS Nr 789443-26-1), bis(4-fluorophenyl)iodonium (CAS Nr 167997-65-1), (91290-88-9), (4-nitrophenyl)phenyl iodine (CAS Nr 46734-23-0), and (4-nitrophenyl)(2,4,6-trimethylphenyl)iodine (CAS Nr 1146127-10-7).

[0179] Preferably, the diaryliodonium salt is a compound of general formula (II):

[0180]

[0181] in

[0182] R 1 -R 10 They are independently selected from hydrogen, C1-C 18 -alkyl and C1-C 12 -alkoxy; and

[0183] An - It is selected from BF4 - B(C6F5)4 - PF6 - AsF6 - SbF6 - CF3SO3 - (CH3C6H4)SO3 - (C4F9)SO3 - (CF3)CO2 - (C4F9)CO2 - and (CF3SO2)3C - The anions in the solution are preferably selected from BF4. - B(C6F5)4 - PF6 - AsF6 - SbF6 - and CF3SO3 - .

[0184] The term "C1-C" used in this article 18 "-alkyl" refers to 1-18 carbon atoms (C1-C2). 18 ) saturated straight-chain or branched monovalent hydrocarbon groups. C1-C 18Examples of -alkyl groups include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, isopropyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, isobutyl, -CH2CH(CH3)2), 2-butyl (s-Bu, sec-butyl, -CH(CH3)CH2CH3), and 2-methyl-2-propyl (t-Bu, tert-butyl). ,-C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (-CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2C) H2CH2CH2CH2CH3), 2-hexyl(-CH(CH3)CH2CH2CH2CH3), 3-hexyl(-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl(-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl(-CH(CH3)CH(CH3)CH2CH3), 4-methyl-2-pentyl(-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl(-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl 2,3-Dimethyl-2-butyl (-CH(CH2CH3)CH(CH3)2), 3,3-Dimethyl-2-butyl (-CH(CH3)C(CH3)3), 1-Heptyl (-CH2(CH2)5CH3), 1-Octyl (-CH2(CH2)6CH3), 1-Nonyl (-CH2(CH2)7CH3), 1-Decyl (-CH2(CH2)8CH3), 1-Undecyl (-CH2(CH2)9CH3), and 2-Dodecyl (-CH2(CH2)) 10 CH3).

[0185] The term "C1-C" 12 "-alkoxy" refers to a C1-C group that is bonded to the rest of the molecule through an oxygen atom. 12 -alkyl group (i.e., 1-12 carbon atoms (C1-C2) 12 (saturated straight-chain or branched monovalent hydrocarbon groups).

[0186] Preferably, in general formula (II), the substituent R1 R 2 R 4 R 5 R 6 R 7 R 9 and R 10 This represents hydrogen. Therefore, preferred cationic photoinitiators are compounds of general formula (II-a):

[0187]

[0188] in

[0189] An - It has the meaning as defined in this article; and

[0190] R 3 and R 8 They are independently selected from hydrogen, C1-C 18 -alkyl and C1-C 12 -alkoxy group, preferably selected from hydrogen and C1-C 18 -alkyl, more preferably selected from hydrogen and C1-C 12 -alkyl, particularly preferably selected from C1-C4-alkyl. Preferably, in general formulas (II) and (II-a), the anion An - Indicates PF6 - .

[0191] Particularly suitable diaryliodonium salts of general formulas (II) and (II-a) are commercially available, known under the names DEUTERONUV 1240 (CAS Nr 71786-70-4), DEUTERON UV 1242 (a mixture of CAS Nr 71786-70-4 and CAS Nr 68609-97-2), DEUTERON UV 2257 (a mixture of CAS Nr 60565-88-0 and CAS Nr 108-32-7), and DEUTERON UV 1250 (branched bis-((C 10 -C 13 (a mixture of alkylphenyl)-iodonium hexafluoroantimonate and CAS Nr 68609-97-2), and DEUTERON UV 3100 (branched bis-((C7-C 10The following are commercially available: (a mixture of alkylphenyl)-iodonium hexafluorophosphate and CASNr. 68609-97-2) (all available from DEUTERON); OMNICAT 250 (CAS Nr 344562-80-7), OMNICAT 440 (CAS Nr 60565-88-0), and OMNICAT 445 (a mixture of CAS Nr 60565-88-0 and CAS Nr 3047-32-3) (all available from IGM Resins); and SpeedCure 937 (CAS Nr 71786-70-4), SpeedCure 938 (CAS Nr 61358-25-6), and SpeedCure 939 (CAS Nr 178233-72-2).

[0192] The cationic UV-LED curable protective varnish according to the present invention comprises:

[0193] a) about 65% to about 90% by weight, preferably about 70% to about 90% by weight, of an alicyclic epoxide, or a mixture of an alicyclic epoxide and one or more cationic curable monomers other than the alicyclic epoxide.

[0194] Preferably, the cationic UV-LED curable protective varnish claimed and described herein comprises about 65% to about 90% by weight, preferably about 70% to about 90% by weight, of an alicyclic epoxide and a mixture of one or more cationic curable monomers other than the alicyclic epoxide. More preferably, the cationic UV-LED curable protective varnish claimed and described herein comprises about 70% to about 90% by weight of an alicyclic epoxide and a mixture of one or more cationic curable monomers other than the alicyclic epoxide, wherein the alicyclic epoxide is present in an amount of at least 70% by weight, the weight percentage being based on the total weight of the cationic UV-LED radiation curable protective varnish.

[0195] As is well known to those skilled in the art, alicyclic epoxides are cationic curable monomers containing at least substituted or unsubstituted epoxy cyclohexyl residues:

[0196] Preferably, the alicyclic epoxides described herein comprise at least one cyclohexane ring and at least two epoxy groups. More preferably, the alicyclic epoxides are compounds of general formula (III):

[0197]

[0198] Wherein -L- represents a single bond or a divalent group containing one or more atoms. The alicyclic epoxide of general formula (III) is optionally substituted with one or more straight-chain or branched alkyl groups containing 1 to 10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl and isopropyl).

[0199] In general formula (III), the divalent group -L- can be a straight-chain or branched alkylene group containing 1-18 carbon atoms. Examples of such straight-chain or branched alkylene groups include, but are not limited to, methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene.

[0200] In general formula (III), the divalent group -L- can be a divalent alicyclic hydrocarbon group or a cycloalkylene group, such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene group, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene and cyclohexylidene group.

[0201] In general formula (III), -L- can be a divalent group containing one or more oxygen-containing linking groups, wherein the oxygen-containing linking groups are selected from -C(=O)-, -OC(=O)O-, -C(=O)O-, and -O-. Preferably, the alicyclic epoxide is an alicyclic epoxide of general formula (III), wherein -L- is a divalent group containing one or more oxygen-containing linking groups, wherein the oxygen-containing linking groups are selected from -C(=O)-, -OC(=O)O-, -C(=O)O-, and -O-, more preferably alicyclic epoxides of general formulas (III-a), (III-b), or (III-c) as defined below:

[0202]

[0203] in

[0204] L1 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0205] L2 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, and decyl), preferably containing 1-3 carbon atoms (e.g., methyl, ethyl, n-propyl, and isopropyl); and

[0206] l1 and l2 are independent integers, ranging from 0 to 9, preferably from 0 to 3, and more preferably 0;

[0207]

[0208] in

[0209] L1 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0210] L2 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, and decyl), preferably containing 1-3 carbon atoms (e.g., methyl, ethyl, n-propyl, and isopropyl); and

[0211] l1 and l2 are independent integers, ranging from 0 to 9, preferably from 0 to 3, and more preferably 0;

[0212] -L3- is a single bond or a straight-chain or branched divalent hydrocarbon group containing 1-10 carbon atoms, preferably 3-8 carbon atoms, such as alkylene groups including trimethylene, tetramethylene, hexamethylene and 2-ethylhexene, and cyclohexene groups, such as 1,2-cyclohexene, 1,3-cyclohexene, 1,4-cyclohexene and cyclohexylidene;

[0213]

[0214] in

[0215] L1 can be the same or different each time it appears, and it is a straight-chain or branched alkyl group containing 1-3 carbon atoms, such as methyl, ethyl, n-propyl and isopropyl.

[0216] L2 can be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-3 carbon atoms, such as methyl, ethyl, n-propyl, and isopropyl; and

[0217] l1 and l2 are independent integers, ranging from 0 to 9, preferably from 0 to 3, and more preferably 0.

[0218] Preferred alicyclic epoxides of general formula (III-a) include, but are not limited to: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexane carboxylate, 3,4-epoxy-2-methylcyclohexylmethyl-3,4-epoxy-2-methyl-cyclohexane carboxylate, and 3,4-epoxy-4-methylcyclohexylmethyl-3,4-epoxy-4-methylcyclohexane carboxylate.

[0219] Preferred alicyclic epoxides of general formula (III-b) include, but are not limited to: bis(3,4-epoxycyclohexylmethyl) adipic acid, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid, bis(3,4-epoxycyclohexylmethyl) oxalate, bis(3,4-epoxycyclohexylmethyl) pimecrolate, and bis(3,4-epoxycyclohexylmethyl) sebacate.

[0220] The preferred alicyclic epoxide of general formula (III-c) is 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-m-dioxane.

[0221] Other alicyclic epoxides include alicyclic epoxides of general formula (IV-a) and general formula (IV-b), which are optionally substituted with one or more straight-chain or branched alkyl groups containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl, and decyl), preferably containing 1-3 carbon atoms (e.g., methyl, ethyl, n-propyl, and isopropyl).

[0222]

[0223] The alicyclic epoxides described herein may be hydroxyl-modified or (meth)acrylate-modified. Examples are commercially available under the names Cyclomer A400 (CAS: 64630-63-3) and Cyclomer M100 (CAS No.: 82428-30-6) (DaicelCorp.) or TTA 15 and TTA16 46 (TetraChem / Jiangsu).

[0224] The one or more cationic curable monomers other than the alicyclic epoxides described herein are selected from: vinyl ethers, allyl ethers, cyclic ethers other than alicyclic epoxides (including epoxides other than alicyclic epoxides), oxetanes and tetrahydrofurans, lactones, cyclic sulfides, vinyl sulfides, allyl sulfides, hydroxyl-containing compounds and mixtures thereof, preferably selected from: vinyl ethers, cyclic ethers other than alicyclic epoxides, especially oxetanes and mixtures thereof.

[0225] Vinyl ethers are known in the art to accelerate curing and reduce tack, thereby limiting the risk of blocking and set-off when coated sheets are stacked immediately after coating. They also improve the physical and chemical resistance of the protective coating and enhance its flexibility and adhesion to substrates, which is particularly advantageous when coating plastic and polymeric substrates. Vinyl ethers also help reduce the viscosity of varnishes while strongly copolymerizing with the varnish vehicle. Examples of preferred vinyl ethers used in the cationic UV-LED radiation-curable protective varnishes claimed herein 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, cyclohexyl vinyl ether, cyclohexanediethanol monovinyl ether, cyclohexanediethanol divinyl ether, 4-(ethoxymethyl)cyclohexylmethyl benzoate, phenyl vinyl ether, methyl phenyl vinyl ether, methoxyphenyl vinyl ether, 2-chloroethyl vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 1,6-hexanediol monovinyl ether, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, 4-(ethoxy)butyl benzoate, bis[4-]adipic acid. [4-(Ethyloxy)butyl ester], bis[4-(Ethyloxy)butyl succinate], bis[4-(Ethyloxymethyl)cyclohexyl methyl glutarate], 4-(Ethyloxy)butyl stearate, trimethylolpropane trivinyl ether, propylene carbonate ether, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, ethylene glycol butyl vinyl ether, dipropylene glycol divinyl ether, triethylene glycol divinyl ether, triethylene glycol methyl vinyl ether, triethylene glycol monobutyl vinyl ether, tetraethylene glycol diethylene glycol... Alkenyl ethers, poly(tetrahydrofuran)divinyl ethers, polyethylene glycol-520 methyl vinyl ether, pluriol-E200 divinyl ether, tris[4-(ethoxy)butyl]trimethacrylate, 1,4-bis(2-ethoxyethoxy)benzene, 2,2-bis(4-ethoxyethoxyphenyl)propane, bis[4-(ethoxy)methyl]cyclohexyl]methyl]terephthalate, bis[4-(ethoxy)methyl]cyclohexyl]methyl]isophthalate. Suitable vinyl ethers are sold by BASF under the names EVE, IBVE, DDVE, ODVE, BDDVE, DVE-2, DVE-3, CHVE, CHDM-di, HBVE. One or more vinyl ethers described herein may be hydroxyl-modified or (meth)acrylate-modified (e.g., VEEA, 2-(2-ethoxyethoxy)ethyl acrylate, from Nippon Shokubai (CAS: 86273-46-3)).

[0226] The use of epoxides other than alicyclic epoxides in the cationic UV-LED radiation-curable protective varnishes claimed and described herein helps to accelerate curing and reduce tackiness, as well as reduce the viscosity of the varnish, while strongly copolymerizing with the varnish carrier. Preferred examples of epoxides other than alicyclic epoxides described herein include, but are not limited to: cyclohexanediol diglycidyl ether, poly(ethylene glycol) diglycidyl ether, poly(propylene glycol) diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, bisphenol A diglycidyl ether, neopentyl glycol diglycidyl ether, trimethylolpropane triglycidyl ether, glycerol triglycidyl ether, pentaerythritol tetraglycidyl ether, butyl glycidyl ether, p-tert-butylphenyl glycidyl ether, hexadecyl glycidyl ether, 2-ethylhexyl glycidyl ether, octyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, tetradecyl glycidyl ether, C 12 / C 14 -alkyl glycidyl ether, C 13 / C 15 - Alkyl glycidyl ethers and mixtures thereof. Suitable epoxides other than alicyclic epoxides are marketed under the trademark of EMSGriltech. (For example (V51-63 or RV 1806) for sale.

[0227] According to a preferred embodiment of the present invention, a cationic UV-LED radiation-curable protective varnish claimed and described herein comprises:

[0228] a) A mixture of about 65% to about 90% by weight, preferably about 70% to about 90% by weight, of an alicyclic epoxide and one or more oxetanes.

[0229] Oxycyclic butanes are known in the art to accelerate curing and reduce tack, thereby limiting the risk of sticking and smudging when printed sheets are stacked immediately after coating. They also help reduce the viscosity of varnishes while strongly copolymerizing with the varnish carrier. Preferred examples of oxetanes include trimethylolpropane, 3,3-dimethyloxetane, trimethylolpropaneoxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane, 3,3-dicyclomethyloxetane, 3-ethyl-3-phenoxymethyloxetane, bis([1-ethyl(3-oxetane)]methyl) ether, 1,4-bis[3-ethyl-3-oxetanemethoxy)methyl]benzene, 3,3-dimethyl-2(p-methoxy-phenyl)oxetane, 3-ethyl-[(triethoxysilylpropoxy)methyl]oxetane, 4,4-bis(3-ethyl-3-oxetane)methoxymethyl]biphenyl, and 3,3-dimethyl-2(p-methoxy-phenyl)oxetane. The one or more oxobutanes described herein may be hydroxyl-modified (e.g., Curalite from Perstorp). TM Ox (CAS Nr: 3047-32-3) or (meth)acrylate modified (e.g., UVi-Cure S170 from Lambson (CAS Nr: 37674-57-0)).

[0230] This document claims protection for and describes the following cationic UV-LED radiation-curable protective varnishes:

[0231] c) about 0.01% by weight to about 5% by weight, preferably about 0.05% by weight to about 3% by weight, more preferably about 0.1% by weight to about 2% by weight, and even more preferably about 0.2% by weight to about 1% by weight of nonionic surfactant.

[0232] As is well known to those skilled in the art, nonionic surfactants comprise both hydrophilic and hydrophobic portions and are uncharged. Preferably, the nonionic surfactants used in the cationic UV-LED curable protective varnishes claimed and described herein have a molecular weight between about 200 g / mol and about 3000 g / mol, and / or contain more than one functional group selected from hydroxyl and epoxy groups. More preferably, the nonionic surfactants are selected from nonionic fluorinated surfactants and nonionic silicone surfactants.

[0233] As used herein, the term “nonionic fluorinated surfactant” includes nonionic perfluoropolyether surfactants and nonionic fluorinated surfactants.

[0234] As used herein, the term "nonionic perfluoropolyether surfactant" refers to a nonionic surfactant comprising a perfluoropolyether backbone and one or more, preferably two or more, terminal functional groups selected from hydroxyl, epoxide, acrylate, methacrylate, and trialkoxysilyl groups, preferably selected from hydroxyl and epoxide groups. Preferably, the nonionic perfluoropolyether surfactant is characterized by an average molecular weight (M... n The concentration is less than about 2000 [g / mol]. As used herein, the perfluoropolyether backbone refers to the residues of a perfluoropolyether polymer containing randomly distributed repeating units selected from perfluoromethyleneoxy (-CF2O-) and perfluoroethyloxy (-CF2-CF2O-). The perfluoropolyether residues are directly or via a spacer selected from methylene (oxyvinyl), 1,1-difluoroethylene-(oxyvinyl), methylene-di(oxyvinyl), 1,1-difluoroethylene-di(oxyvinyl), methylene-tri(oxyvinyl), 1,1-difluoroethylene-tri(oxyvinyl), methylene-tetra(oxyvinyl), 1,1-difluoroethylene-tetra(oxyvinyl), methylene-penta(oxyvinyl), 1,1-difluoroethylene-penta(oxyvinyl) and straight-chain or branched hydrocarbon groups, and optionally fluorinated at the carbon atom of the carbon atom connecting the spacer to the perfluoropolyether residue. The residues contain one or more urethane groups, or one or more amide groups, and optionally one or more cyclic moieties, including saturated cyclic moieties (such as cyclohexylene) and aromatic cyclic moieties (such as phenylene). Preferably, the nonionic perfluoropolyether surfactant is functionalized with one or more hydroxyl and / or epoxide functional groups.

[0235] Preferably, the nonionic perfluoropolyether surfactant is a compound of general formula (V) with an average molecular weight (M). n The concentration is approximately 1200 g / mol to approximately 2000 g / mol.

[0236]

[0237] in

[0238] f and e are independent integers, chosen from 1, 2, and 3;

[0239] FG 1 and FG 2 These are terminal functional groups that are independently selected from the following groups:

[0240] -OH, -OC(O)CH=CH2, -OC(O)C(CH3)=CH2, and -Si(OR 20 3;

[0241] R 20It is a C1-C4 alkyl group;

[0242] -S 1 - indicates a single bond or a spacer selected from the following:

[0243]

[0244] in

[0245] -J 1 -Selected from

[0246] in

[0247] j 1 It is an integer between 1 and 12, preferably between 4 and 10;

[0248] L5 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0249] L6 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0250] l5 and l6 are independent integers, ranging from 0 to 4, preferably from 0 to 1; and

[0251] -J 3 - Selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-;

[0252] -J 2 -Selected from

[0253] a is an integer between 1 and 6, preferably between 1 and 3; and

[0254] b is an integer between 1 and 6, preferably between 2 and 4;

[0255] -S 2 - indicates a single bond or a spacer base selected from the following:

[0256]

[0257]

[0258] in

[0259] -J 4 -Selected from

[0260] in

[0261] j 4 It is an integer between 1 and 12, preferably between 4 and 10;

[0262] L7 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0263] L8 may be the same or different each time it appears, and is a straight-chain or branched alkyl group containing 1-10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hexyl, octyl and decyl), preferably containing 1-3 carbon atoms (e.g. methyl, ethyl, n-propyl and isopropyl).

[0264] l7 and l8 are independent integers, ranging from 0 to 4, preferably from 0 to 1; and

[0265] -J 6 - Selected from -O-, -CH2-, -CH(CH3)- and -C(CH3)2-;

[0266] -J 5 -Selected from

[0267] in

[0268] r is an integer between 1 and 6, preferably between 1 and 3; and

[0269] w is an integer between 1 and 6, preferably between 2 and 4;

[0270] and

[0271] Where s and t are the average molecular weights (M) of compounds of general formula (V). n The integer is chosen from approximately 1200 [g / mol] to approximately 2000 [g / mol].

[0272] Preferably, in general formula (V), FG 1 and FG 2They can be expressed independently as -OC(O)CH=CH2 or -OC(O)C(CH3)=CH2;

[0273] -S 1 -express Where b has the meaning defined in this article; and

[0274] -S 2 -express Where w has the meaning defined in this article.

[0275] More preferably, in general formula (V), FG 1 and FG 2 It represents -OH;

[0276] -S 1 - indicates a single key or Where 'a' has the meaning defined in this article;

[0277] -S 2 - indicates a single key or Where r has the meaning defined in this article; the sum of o and r is between 3 and 9.

[0278] More preferably, in general formula (V), FG 1 and FG 2 Represents -Si(OR) 20 3;

[0279] R 20 It is a C1-C4 alkyl group, preferably ethyl;

[0280] -S 1 -express Where b has the meaning defined in this article; and

[0281] -S 2 -express Where w has the meaning defined herein. Therefore, the preferred perfluoropolyether surfactant is a compound of the general formula (Va):

[0282]

[0283] in

[0284] b and w are integers between 1 and 6, preferably between 2 and 4;

[0285] s is an integer between 2 and 6; and

[0286] q is an integer between 2 and 4.

[0287] A particularly suitable example of a nonionic perfluoropolyether surfactant is Solvay, named after it. E10H, MD700 MD500 AD1700 E-series and S10 is commercially available.

[0288] As used herein, the term "nonionic fluorinated surfactant" refers to a surfactant containing a perfluoroalkyl chain CF3 (CF2). x The nonionic surfactant, wherein x is an integer from 2 to 18. Preferably, the nonionic fluorosurfactant is characterized by an average molecular weight (M... n The concentration is approximately 200 g / mol to approximately 2000 g / mol.

[0289] Preferably, the nonionic fluorosurfactant is a compound of general formula (VI):

[0290] CF3 (CF2) x (CH2) y E

[0291] (VI)

[0292] in

[0293] x is an integer between 2 and 18;

[0294] y is an integer from 0 to 8; and

[0295] E is selected from -(CR2CR2O) z H, and -OSi(OR) 20 )3,

[0296] Where z is an integer between 0 and 15;

[0297] R can be the same or different each time it appears, and is selected from hydrogen and methyl; and

[0298] R 20 It is a C1-C4 alkyl group. In general formula (VI), R preferably represents hydrogen.

[0299] Particularly preferred are nonionic fluorinated surfactants of general formula (VI-a):

[0300] CF3 (CF2) x (CH2) y (CR2CR2O) z H(VI-a)

[0301] in

[0302] x is an integer between 2 and 18;

[0303] y is an integer between 0 and 8;

[0304] z is an integer between 0 and 15; and

[0305] R may be the same or different each time it appears, and is selected from hydrogen and methyl, preferably hydrogen. Nonionic fluorinated surfactants of general formula (VI-a) include CHEMGUARD S550-100 or CHEMGUARD S550, CHEMGUARD S222N, CHEMGUARD S559-100 or CHEMGUARD S559 (all commercially available from CHEMGUARD); Capstone TM FS-31, Capstone TM FS-35, Capstone TM FS-34, Capstone TM FS-30, Capstone TM The name FS-3100 (fully commercialized by Chemours) is commercially available.

[0306] Preferably, it is a nonionic fluorinated surfactant of general formula (VI-b):

[0307] CF3 (CF2) x (CH2) y OSi(OR 20 (VI-b),

[0308] in

[0309] x is an integer between 2 and 18;

[0310] y is an integer from 0 to 8; and

[0311] R 20 It is a C1-C4 alkyl group. Nonionic fluorinated surfactants of general formula (VI-b) are commercially available under the names Dynasylan F8261 and Dynasylan F8263 (commercialized by Evonik).

[0312] Preferably, it is a nonionic fluorinated surfactant of the general formula (VI-c):

[0313]

[0314] in

[0315] x is an integer between 2 and 18;

[0316] y is an integer from 0 to 8; and

[0317] R 21Selected from hydrogen and methyl. Examples of nonionic fluorinated surfactants of general formula (VI-c) include, but are not limited to: 1H,1H,2H,2H-octyl perfluoroacrylate (Sigma-Aldrich), 1H,1H,2H,2H-octyl perfluoromethacrylate (Sigma-Aldrich), 1H,1H-octyl perfluoroacrylate (Sigma-Aldrich), 1H,1H-octyl perfluoromethacrylate (Sigma-Aldrich), 1H,1H-heptyl perfluoroacrylate (Sigma-Aldrich), and 1H,1H-heptyl perfluoromethacrylate (Sigma-Aldrich).

[0318] As used herein, nonionic silicone surfactants refer to nonionic surfactants containing a silicone backbone, wherein the silicone backbone contains a compound selected from di(methyl)siloxane (-(CH3)2SiO-) and / or methyl-(C2-C) 10 -alkyl)-siloxane(-(CH3)(C2-C 10 Randomly distributed repeating units of (-alkyl)SiO-), wherein one or more methyl groups and / or C2-C 10 -alkyl groups can be independently substituted by: aryl groups, polyesters, optionally with terminal functional groups selected from hydroxyl, epoxide, and (meth)acrylate groups, polyethers, such as polyalkylene glycols (including polyethylene glycol and polypropylene glycol), optionally with terminal functional groups selected from hydroxyl, epoxide, and (meth)acrylate groups, hydroxyl, epoxide, or (meth)acrylate groups, and / or wherein the silicone backbone can be directly or via spacer groups linked to terminal functional groups selected from hydroxyl, epoxide, and (meth)acrylate groups. The silicone backbone described herein can be linked to aliphatic polyurethane acrylates or fluorinated aliphatic polyurethane acrylates. Preferably, the nonionic silicone surfactant is characterized by an average molecular weight of less than about 3000 [g / mol].

[0319] Nonionic silicone surfactants include, but are not limited to: polymethylalkylsiloxanes, such as BYK-077 and BYK-085 sold by BYK; polyester-modified polydimethylsiloxanes, such as BYK310 sold by BYK; polyether-modified polydimethylsiloxanes, such as BYK-377, BYK-333, BYK-345, BYK-346, and BYK-348 sold by BYK; polyester-modified polymethylalkylsiloxanes, such as BYK-315 sold by BYK; polyether-modified polymethylalkylsiloxanes, such as BYK-341, BYK-320, and BYK-325 sold by BYK; and hydroxyl-functionalized polydimethylsiloxanes, such as those sold by Evonik. HSI-2311, polyester-modified hydroxyl-functionalized polydimethylsiloxane, such as BYK-370 and BYK-373 sold by BYK; polyether-modified hydroxyl-functionalized polydimethylsiloxane, such as BYK-308 sold by BYK; polyether-polyester-modified hydroxyl-functionalized polydimethylsiloxane, such as BYK-375 sold by BYK; epoxy-functionalized polydimethylsiloxane, such as sold by Evonik. E-Si 2330, acryloyloxy-functionalized polydimethylsiloxane, such as that sold by Evonik. V-SI 2250 and Rad 2700, polyester-modified acrylic-functionalized polydimethylsiloxane, such as BYK-371 sold by BYK, and polyether-modified acrylic-functionalized polydimethylsiloxane, such as sold by Evonik. Rad 2100 and Rad 2500, silicone-modified aliphatic polyurethane acrylates, such as SUO-S3000 and SUO-S600NM sold by Polygon, silicone and fluorine-modified aliphatic polyurethane acrylates, such as SUO-FS500 sold by Polygon.

[0320] To facilitate the storage, stacking, and retrieval of secure documents, particularly banknotes, this document claims and describes a cationic UV-LED radiation-curable protective varnish that may contain a matte agent, providing a matte protective coating with improved grip. Furthermore, the matte protective coating has the advantage of maintaining the user's habitual perception of the secure document through touch and causes significantly less reflection than a glossy protective coating, thereby enabling machine inspection and authentication of the secure document using conventionally used optical sensors. The matte agent may be present in an amount from about 1% to about 12% by weight, where the weight percentage (wt%) is based on the total weight of the cationic UV-LED radiation-curable protective varnish.

[0321] As is well known to those skilled in the art, matting agents should be avoided in cationic UV-LED radiation-curable protective varnishes intended for use in the production of glossy protective coatings, which can be used, for example, to protect surfaces containing overt security features present in security documents. The cationic UV-LED radiation-curable protective varnish claimed and described herein is free of matting agents and provides a glossy protective coating that is eye-catching and draws the attention of lay users to the security features covered by the gloss varnish, thereby helping inexperienced users easily locate security features on security documents. This cationic UV-LED radiation-curable protective varnish can be applied directly to the surface of the security features present in the security document. Furthermore, as described in International Patent Application Publication No. WO2011120917A1, this matting agent-free cationic UV-LED radiation-curable protective varnish can be used to produce glossy, discontinuous protective coatings for security documents, presenting both a matte protective coating applied directly to the surface of the security document and a glossy protective coating partially covering the surface of the matte protective coating.

[0322] The matting agent is preferably selected from inorganic particles and resin particles. Examples of inorganic particles and resin particles include, but are not limited to: thermoplastic polymer matting agents, such as thermoplastic polymer microspheres and micronized polyolefin waxes; calcium carbonate matting agents, such as those produced by Omya under the trade name... 100 offers core / shell microparticles containing a calcium carbonate core and a hydroxyapatite shell, alumina matting agents, aluminosilicate matting agents, and amorphous silica particles with porous structures, such as fumed amorphous silica particles, precipitated amorphous silica particles, and amorphous silica particles obtained from the sol-gel method.

[0323] Preferably, the matting agent is selected from amorphous silica particles with a porous structure, including organically surface-treated amorphous silica particles. This matting agent exhibits a low refractive index, resulting in good transmittance. A preferred feature of the matting agent is that its D50 value, determined by laser diffraction, is in the range of about 1 μm to about 25 μm, more preferably 2 μm to about 15 μm, and more preferably between about 3 μm and about 10 μm.

[0324] Suitable amorphous silica particles with porous structures are named as follows: (from Grace) (e.g.) C906, Rad 2105, 7000, ED30), (from Evonik) (e.g.) OK412, OK500, OK520, OK607, OK900, 3600, TS100), PPG (from PPG) (e.g., PPG) 66, 2023, 8100, 8300) (from PQ Corporation) (e.g.) The UV55C, UV70C, HP210, HP240, HP380, and HP860 models are commercially available.

[0325] The cationic UV-LED radiation-curable protective varnish may contain up to 10% by weight of organic solvent, the weight percentage being based on the total weight of the cationic UV-LED radiation-curable protective varnish. Preferably, the organic solvent is present in an amount from about 1% to about 7.5% by weight, more preferably from about 2% to about 5% by weight. Preferably, the organic solvent is a polar organic solvent selected from alcohols, glycols, glycol ethers, glycol esters, and cyclic carbonates, preferably having a boiling point above about 80°C, more preferably above about 100°C. The cationic UV-LED radiation-curable protective varnish claimed and described herein may further contain one or more additives, including but not limited to antifoaming agents, defoaming agents, UV absorbers, antisettling stabilizers, antimicrobial agents, viricides, biocidal agents, fungicides, and combinations thereof.

[0326] The cationic UV-LED radiation-curable protective varnish described and claimed herein can be prepared by mixing an alicyclic epoxide or a mixture of an alicyclic epoxide and one or more cationic curable monomers other than an alicyclic epoxide with an organic solvent (if present), one or more additives (if present), a matting agent (if present), a nonionic surfactant, a photosensitizer of general formula (I), and a diaryliodomonium salt. Preferably, the solid components of the cationic UV-LED radiation-curable protective varnish are dispersed in a mixture of the liquid components contained in the protective varnish. The nonionic surfactant, the photosensitizer of general formula (I), and the diaryliodomonium salt can be added to the mixture simultaneously or sequentially during the dispersion or mixing steps of all other components, or at a later stage (i.e., just before the cationic UV-LED radiation-curable protective varnish is applied to the substrate surface of the security document and / or the surface of one or more security features of the security document).

[0327] Preferably, the cationic UV-LED radiation curable protective varnish is a flexographic printing varnish, an inkjet printing varnish, or a screen printing varnish, more preferably a flexographic printing varnish.

[0328] In a preferred embodiment, the cationic UV-LED radiation-curable protective varnish is a flexographic printing varnish. Flexographic printing preferably uses a unit having a doctor blade, preferably a chambered doctor blade, an anilox roller, and a plate cylinder. The anilox roller advantageously has small units whose volume and / or density determine the application speed of the curable varnish. The doctor blade abuts against the anilox roller and simultaneously scrapes away any remaining varnish. The anilox roller transfers the varnish to the plate cylinder, and finally to the substrate. Specific designs can be implemented using designed photopolymer plates. The plate cylinder can be made of polymer or elastomer materials. Polymers are primarily used as photopolymers in the plate and sometimes as seamless coatings on sleeves. The photopolymer plate is made of a photosensitive polymer that is cured by ultraviolet (UV) light. The photopolymer plate is cut to the desired size and placed in a UV light exposure unit. One side of the plate is fully exposed to UV light to harden or cure the base of the plate. The plate is then flipped over, a working negative is mounted on the uncured side, and the plate is further exposed to UV light. This hardens the plate in the image area. The plate is then processed to remove the unhardened photopolymer from the non-image areas, which lowers the plate surface in these non-image areas. After processing, the plate is dried and subjected to a post-exposure dose of UV light to cure the entire plate. The preparation of the printing cylinder for flexographic printing is described in J.M.A. Dams and P.A. Dolin's Printing Technology (Delmar Thomson Learning, 5th ed., pp. 359-360). For suitability for printing by flexographic printing, the cationic UV-LED radiation-curable protective varnish must have a viscosity in the range of about 50-500 mPas at 25°C, which is measured at 100 rpm using a Brookfield viscometer (model "DV-IPrime") equipped with a rotor S21 for measuring viscosities in the range of 100-500 mPas at 25°C, or using a viscometer for measuring viscosities in the range of 100-500 mPas at 25°C and 1000 rpm. -1 Viscosities below 100 mPas were measured using a TA Instruments DHR-2 rotational viscometer (conical-planar geometry, 40 mm diameter).

[0329] In another preferred embodiment of the invention, the cationic UV-LED radiation-curable protective varnish is an inkjet printing varnish, preferably a drop-on-demand (DOD) inkjet printing varnish. DOD printing is a non-contact printing process in which droplets are generated only when printing is required, and typically by a jetting mechanism rather than by destabilizing the jet. DOD printing is classified into piezoelectric pulse, thermal jet, and valve jet printing, depending on the mechanism used to generate the droplets in the printhead. For suitability for DOD inkjet printing, the cationic UV-LED radiation-curable protective varnish must have a low viscosity of less than about 20 cP and a surface tension of less than about 45 N / m at the jetting temperature.

[0330] In a still preferred embodiment of the invention, the cationic UV-LED radiation-curable protective varnish is a screen-printed varnish. As is well known to those skilled in the art, screen printing (also known in the art as silkscreen printing) is a printing technique that typically uses a screen made of woven mesh to support an ink-blocking stencil. The attached stencil forms a mesh-like open area, transferring the varnish as a sharply defined image onto the substrate. A squeegee moves through the screen with the ink-blocking stencil, forcing the varnish through the threads of the woven mesh in the open areas. A significant feature of screen printing is that a thicker varnish can be applied to the substrate compared to other printing techniques. Therefore, screen printing is preferred when a varnish deposit with a thickness between approximately 10-50 μm or greater is required, which cannot be (easily) achieved with other printing techniques. Typically, a screen is made of a porous, finely woven fabric called a mesh stretched onto a frame, such as aluminum or wood. Currently, most meshes are made of synthetic materials such as synthetic threads or steel wire. Preferred synthetic materials are nylon or polyester threads. In addition to wire meshes manufactured based on woven meshes of synthetic or metal wires, wire meshes have been developed from solid metal sheets with perforated grids. Such wire meshes are prepared by a method comprising: forming a wire mesh skeleton on a matrix provided with a separating agent in a first electrolytic cell; peeling the formed wire mesh skeleton from the matrix; and electrolyzing the wire mesh skeleton in a second electrolytic cell to deposit metal onto the skeleton, thereby electrolytically forming a metal wire mesh.

[0331] There are three types of screen printing machines: flatbed, rotary, and rotary screen printing machines. Flatbed and rotary screen printing machines are similar in that they both use a flat screen and a three-step reciprocating process to perform the printing operation. First, the screen is moved to a position on the substrate, then a squeegee presses against the screen and draws on the image area, and then the screen is lifted off the substrate to complete the process. With a flatbed press, the substrate to be printed is typically placed on a horizontal printing platform parallel to the screen. With a rotary press, the substrate is mounted on a cylinder. Flatbed and rotary screen printing processes are discontinuous processes, therefore speeds are limited, typically a maximum of 45 m / min in web printing and a maximum of 3,000 sheets / hour in sheet-fed processes.

[0332] In contrast, rotary screen printing presses are designed for continuous, high-speed printing. The screen used on a rotary screen printing press is, for example, a thin metal cylinder typically obtained using the electroforming method described above, or a thin metal cylinder made of braided steel wire. The cylinder, with its open ends, is capped at both ends and mounted in blocks on the side of the printing press. During printing, varnish is pumped into one end of the cylinder, ensuring a continuous fresh supply. The squeegee is fixed inside the rotating screen, and the squeegee pressure is maintained and adjusted to achieve good and consistent print quality. The advantage of rotary screen printing presses is that speeds in roll-to-roll processes can easily reach 150 m / min, and speeds in sheet-fed processes can easily reach 10,000 sheets / hour.

[0333] Screen printing is further described in, for example, RHLeach and RJPierce's *The Printing Ink Manual* (Springer Edition, 5th Edition, pp. 58-62), JMAdams and PADolin's *Printing Technology* (Delmar Thomson Learning, 5th Edition, pp. 293-328), and H. Kipphan's *Handbook of Print Media* (Springer, pp. 409-422 and 498-499).

[0334] The cationic UV-LED radiation-curable protective varnish claimed and described herein can be cured by exposure to UV light emitted by one or more UV-LED light sources, preferably by exposure to one or more wavelengths between about 365 nm and about 405 nm, more preferably by exposure to UV light at 365 nm and / or 385 nm and / or 395 nm. As is well known to those skilled in the art, the cationic UV-LED radiation-curable protective varnish claimed and described herein is also suitable for curing using a medium-pressure mercury lamp.

[0335] According to another aspect of the invention, there is a method for coating a security document, the security document comprising a substrate and one or more security features applied to or inserted into a portion of the substrate, wherein the method comprises the following steps:

[0336] i) Preferably, the cationic UV-LED radiation-curable protective varnish claimed and described herein is applied to the substrate surface of the security document and / or the surface of one or more security features using a printing method selected from flexographic printing, inkjet printing, and screen printing to form a varnish layer; and

[0337] ii) Curing the varnish layer by exposing it to UV light emitted by a UV-LED source to form a protective coating covering the substrate surface of the security document and / or one or more security features.

[0338] Preferably, at least one of the security features applied to or inserted into a portion of the substrate of the security document to be coated is a UV light-excited luminescent security feature, i.e. a security feature that emits light in response to excitation by UV light, particularly UV light with wavelengths of 254 nm or 366 nm.

[0339] Preferably, step ii) described herein comprises: exposing a varnish layer to one or more wavelengths emitted by one or more UV-LED sources in the range of about 365 nm to about 405 nm to form a protective coating covering the surface of the substrate of the security document and / or the surface of one or more security features. Typically, commercially available UV-LED sources use one or more wavelengths, such as 365 nm, 385 nm, 395 nm, and 405 nm. Preferably, step ii) described herein comprises: exposing a varnish layer to a single wavelength emitted by a UV-LED source in the range of 365 nm to 405 nm, such as 365 nm, 385 nm, 395 nm, or 405 nm, to form a protective coating covering the surface of the substrate of the security document and / or the surface of one or more security features. The varnish layer preferably has an intensity of at least 150 mJ / cm². 2 The dosage, more preferably at least 200 mJ / cm 2 The dosage, and particularly preferably at least 200 mJ / cm².2 The dose of UV light exposure is at least 220 mJ / cm². 2 This process allows the clear coat to cure and form a protective coating covering the substrate surface and / or one or more security features of the security document. As described below, UV Power from EIT, Inc., USA, can be used. II. Radiation meter to measure dose.

[0340] As used herein, the term "substrate" includes any secure document substrate in which security features may be inserted and / or applied. Secure document substrates include, but are not limited to, paper or other fibrous materials such as cellulose, paper-containing materials, plastics and polymers, composite materials, and mixtures or combinations thereof. Typical paper, paper-like, or other fibrous materials are made from a variety of fibers, including but not limited to Manila hemp, cotton, flax, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton / flax blends are preferred for banknotes, while wood pulp is commonly used for non-banknote security documents. Typical examples of plastics and polymers include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), poly(1,4-butanediol terephthalate) (PBT), and polyethylene (2,6-naphthoic acid glycol) (PEN), and polyvinyl chloride (PVC). Typical examples of composite materials include, but are not limited to, multilayer structures or laminates of paper and at least one plastic or polymer material, such as those described above. The substrate of the security document can be printed with any desired markings, including any symbols, images, and patterns, and / or may include one or more security features, including luminescent security features. Another aspect of the invention relates to a security document comprising a substrate, one or more security features applied to or inserted into a portion of the substrate, and a protective coating covering the surface of the substrate and / or the surface of the one or more security features, wherein the protective coating is obtained by a coating method claimed and described herein, the coating method comprising the following steps:

[0341] i) Preferably, the cationic UV-LED radiation-curable protective varnish claimed and described herein is applied to the surface of the substrate of the security document and / or the surface of one or more security features by a printing method selected from flexographic printing, inkjet printing, and screen printing, more preferably by flexographic printing, to form a varnish layer; and

[0342] ii) Curing the varnish layer by exposing it to UV light emitted by a UV-LED source to form a protective coating covering the substrate surface of the security document and / or one or more security features.

[0343] The security document according to the invention may include an uncoated area of ​​about 5% to about 15% of the substrate surface on one side, where the percentage is based on the total surface area of ​​the security document. Preferably, the uncoated area is present on at least one edge or corner of the substrate. The uncoated area can be used, for example, for numbering the security document. If the security document is a banknote, the uncoated area can also be used to absorb staining (non-erasable) ink used to protect the banknote from theft and robbery, as described in International Patent Application Publication No. WO2013127715A2.

[0344] Another aspect of the invention relates to a protective coating for a security document, the security document comprising a substrate and one or more security features applied to or inserted into a portion of the substrate, wherein the protective coating is obtained by a cationic UV-LED radiation-curable protective varnish claimed and described herein. Specifically, the aforementioned protective coating is obtained by:

[0345] i) Preferably, a cationic UV-LED radiation-curable protective varnish claimed and described herein is applied to the surface of the substrate of the security document and / or the surface of one or more security features by a printing method selected from flexographic printing, inkjet printing, and screen printing, more preferably by flexographic printing, to form a varnish layer; and

[0346] ii) Curing the varnish layer by exposing it to UV light emitted by a UV-LED source to form a protective coating covering the substrate surface of the security document and / or one or more security features.

[0347] Preferably, at least one of the security features applied to or inserted into a portion of the substrate of the security document to be coated is a UV light-excited luminescent security feature, i.e. a security feature that emits light in response to UV light, particularly UV light with a wavelength of 254 nm or 366 nm.

[0348] As used herein, the term "secure document" refers to a valuable document that, for example, makes it potentially easy to attempt to forge or illegally copy, and is typically protected against forgery or fraud by at least one security feature. Typical examples of secure documents include, but are not limited to, banknotes, contracts, bills, checks, vouchers, stamp duty and tax labels, agreements, and identification documents such as passports, ID cards, visas, bank cards, credit cards, transaction cards, access documents, and admission tickets.

[0349] Example

[0350] The invention will now be described in more detail with reference to non-limiting embodiments. The following examples and comparative examples provide further details on the preparation of the cationic UV-LED radiation-curable protective varnish according to the invention.

[0351] photosensitizer

[0352] Table 1A

[0353]

[0354] Weight-average molecular weight measurement

[0355] The weight-average molecular weights of the oligomeric photosensitizers S1-S2 were independently determined by GPC (gel permeation chromatography) according to the following method (based on OECD test method 118):

[0356] The Malvern Viskotek GPCmax was used. This instrument is equipped with an isocratic pump, degasser, autosampler, and a triple detector TDA302, which includes a differential refractometer, viscometer, and dual-angle light scattering detectors (7° and 90°). For this specific measurement, only the differential refractometer was used. Calibration curves (log(molecular weight) = f(retention volume)) were established using six polystyrene standards (molecular weight range 472 to 512000 g / mol). Two Viskotek™ 4008L columns (30.0 cm long, 8.0 mm inner diameter) were connected in series with a UV-LED. The stationary phase consisted of particles with a diameter of 6 μm and a maximum pore size of [missing information]. The sample was prepared from a styrene-divinylbenzene copolymer. The temperature was maintained at 35°C during the measurements. The analyzed sample contained 10 mg / mL of the study compound dissolved in THF (Acros, 99.9%, anhydrous) and was injected at a rate of 1 mL / min. The molecular weight of the compound was calculated from the chromatogram as the polystyrene equivalent weight-average molecular weight (PS eq MW) using the following formula, with a 95% confidence level and the average of three measurements at the same solution:

[0357]

[0358] Where H i It is the distance to the preserved volume V i The baseline detector signal level, M i In the retention volume V i The molecular weight of the compound fraction at point n is given, and n is the number of data points. Omnisec 5.12, which is included with the device, is used as the software. The PS eq Mw measured for S1 and S2 is shown in Table 1A above.

[0359] The molar concentration of sulfur in thioxanone-based photosensitizers S1-S4

[0360] The sulfur molar concentration (sulfur (mmol) / photosensitizer (g)) corresponds to the molar concentration of the reactive thioxanone moiety (reactive thioxanone moiety (mmol) / photosensitizer (g)) and is used to ensure that all thioxanone photosensitizers are used at the equivalent molar concentration of the reactive thioxanone moiety.

[0361] The molar concentration of sulfur in oligomeric photosensitizers S1-S2 was determined by ED-XRF.

[0362] The molar concentration of sulfur in oligomeric photosensitizers S1 and S2 was determined by ED-XRF (Spectro XEPOS) using internal standard addition technology and sulfur atom signaling. For each of the oligomeric photosensitizers S1-S2 in Table 1A, three 50 mL solutions of the corresponding photosensitizer at 2 mg / mL in acetonitrile (Sigma-Aldrich, 99.9%) were prepared. 5 mL samples were collected from each solution and an additional 5 mg / mL of Genocure ITX (Rahn, 99.3% according to the certificate of analysis) in acetonitrile was added. Each sample was finished with acetonitrile to a final volume of 10 mL. The solutions obtained are shown in Table 1B.

[0363] Table 1B

[0364] level Solution S1-S2 [mL] Solution ITX [mL] Acetonitrile [mL] 0 5 0 5 1 5 1 4 2 5 3 2 3 5 4 1

[0365] Each sample was independently measured using ED-XRF (Spectro XEPOS) and the spectrum was recorded. Blank measurements (pure acetonitrile) were derived from all spectra. For each series of samples (three measurements), the measured fluorescence intensity at 2.31 keV (SKα1 peak) was shown as a function of the molar concentration (mmol / ml) of sulfur in the added Genocure ITX, and linear regression was performed. The absolute value of the x-intercept of the regression line indicates the sulfur molar concentration at level 0 in each sample. The average values ​​(average of the three measurements) are provided in Table 1C. The corresponding average values ​​were used to determine the sulfur molar concentration (sulfur (mmol) / photosensitizer (g)) in each oligomeric photosensitizer S1-S2 and to calculate the amount (wt%) of oligomeric photosensitizer S1-S2 added for the preparation examples and comparative examples. For thioxanthone photosensitizers S3-S4, the sulfur molar concentration [mmol / g] was calculated directly from their known molecular structures.

[0366] Table 1C summarizes the determined (photosensitizers S1 and S2) and calculated (photosensitizers S3 and S4) sulfur molar concentrations (sulfur (mmol) / photosensitizer (g)) corresponding to the molar concentrations of the reactive thioxanthone fraction (reactive thioxanthone fraction (mmol) / photosensitizer (g)).

[0367] Table 1C

[0368]

[0369] cationic photoinitiator

[0370] Table 1D

[0371]

[0372] Other ingredients

[0373] Table 1E

[0374]

[0375] Preparation of cationic UV-LED radiation-curable protective varnishes (E1-E5 and C1-C9) and the resulting protective coatings

[0376] A1. The cationic UV-LED radiation-curable protective varnish (E1-E5) and comparative experiments (C1-C9) according to the present invention Preparation of (Table 2A)

[0377] 100g of each of the cationic UV-LED curable protective varnishes E1-E5 and comparative varnishes C1-C9 was prepared as follows: First, the first two components (alicyclic epoxide and oxetane) of Table 2A were premixed using Dispermat (model CV-3) (at 1000 rpm for 10 minutes). Then, the matting agent was added and dispersed at 1500 rpm for approximately 15 minutes. Finally, the remaining components were added at 1000 rpm for approximately 10 minutes, and the resulting mixture was further mixed. The cationic UV-LED curable protective varnishes E1-E5 possess viscosity characteristics that make them suitable for flexographic and screen printing.

[0378] A2. Preparation of protective coating

[0379] Varnishes E1-E5 and C1-C9 are applied independently by hand using a manual coating unit (RK-print) with n°0 bar on a fiduciary polymer substrate (CCL Secure Guardian). TM A clear coat with dimensions of approximately 5 cm × 10 cm and a thickness of approximately 4 μm was applied to the sample. Subsequently, a sample was prepared using lamps from IST Metz GmbH (100% lamp power, 70% duty cycle, nominal lamp-to-sample distance of 20 mm), resulting in approximately 220 mJ / cm². 2The varnish layer was exposed twice to UV light at a rate of 150 m / min under a LUV20 UV-LED curing unit emitting at 385 nm, with each layer cured under controlled relative humidity. The dose was measured using a Powerpuck II device under UV-LED conditions similar to those used for curing the sample (same speed and same distance between lamp and sample / detector). The dose was given for the UV-A2 range, selected by a specific filter (370-415 nm) in the device. The conditions used to cure the coated substrate were similar to those expected in an industrial environment.

[0380] Table 2A. Composition of cationic UV-LED radiation-curable protective varnishes E1-E5 and C1-C9

[0381]

[0382] a) Concentration of reactive thioxanone fraction in varnish (reactive thioxanone fraction (mmol) / varnish (100g))

[0383] A3. Evaluation of cationic UV-LED radiation-curable protective varnishes E1-E5 and comparative varnishes using MEK abrasion tests. Curing properties of C1-C9 The protective coating obtained as described in Item A2 above is stored in the dark for 24 hours. After this period, the deep cure performance of each protective coating is evaluated using the following procedure, which is an indicator of the curing performance of the varnish used to obtain the protective varnish:

[0384] - Soak cotton swabs in 99.5% methyl ethyl ketone (MEK) (Brenntag);

[0385] - Gently press and rub each protective coating area (approximately 0.5cm x 5cm) 50 times with a cotton swab. After 30 seconds, visually evaluate the rubbed area. The visual evaluation results summarized in Table 2B are categorized as follows:

[0386] "Poor": The MEK abrasion test resulted in partial or complete removal of the protective varnish, indicating insufficient curing of the protective coating and poor curing performance of the varnish.

[0387] "Acceptable": The MEK abrasion test shows that the protective coating has not been removed, indicating that the curing of the protective coating is acceptable, and the varnish exhibits acceptable curing performance.

[0388] “Optimal”: The MEK abrasion test could not detect it visually, indicating that the curing of the protective coating was optimal, and the varnish exhibited the best curing performance. The varnish with optimal curing performance under the curing conditions described in this article is suitable for industrial production of protective coatings for secure documents.

[0389] Table 2B. Results of MEK Friction Test

[0390]

[0391] a) Curing time determined by MEK friction test after 24 hours.

[0392] A4. Evaluation of fluorescence exhibited by the protective coating exhibiting the best curing performance as determined by the MEK friction test. price

[0393] The fluorescence of protective coatings obtained from varnishes exhibiting the best curing performance as determined by MEK friction tests, specifically those cured by cationic UV-LED radiation, namely protective varnishes E1-E5 and comparative varnishes C2, C4, C6, C8, and C9, was evaluated using the methods described below. Table 2C presents the fluorescence results.

[0394] The residual fluorescence of the protective coating was evaluated at 254 nm and 366 nm using the following parameters with a Fluorolog II (Spex) instrument:

[0395] Detector: R928 / 0115 / 0381

[0396] Angle: 30°

[0397] Position: Front

[0398] Excitation slits: 2nm (254nm) and 2nm (366nm)

[0399] Integrating time: 0.1 seconds

[0400] Wavelength coverage: 400-700nm (in 1nm increments)

[0401] Detection slits: 1nm (254nm) and 1nm (366nm), ultraviolet filters (400nm and below) to avoid detection of excitation light.

[0402] From the obtained spectrum, the maximum fluorescence intensity is determined and the obtained value is reported as an absolute value in photons per second, as shown in Table 2C.

[0403] The absolute intensity (in photons per second) of each protective coating obtained from the cationic UV-LED radiation-curable protective varnishes E1-E5 according to the invention and the comparative varnishes (C2, C4, C6, C8, C9) with the best curing performance was measured and compared with the absolute intensity of the comparative standards (ST1-ST4) at maximum fluorescence. The comparative standards were prepared using cationic varnishes cured under a standard mercury lamp containing compounds that, in the opinion of a person skilled in the art, exhibit low intrinsic fluorescence and / or generate only minimal amounts of fluorescent degradation products during curing. The comparative standards (ST1-ST4) were prepared simultaneously with their protective coatings, which served as comparative standards.

[0404] The residual fluorescence of the comparative standards (ST1-ST4) and the residual fluorescence of their protective coatings, which served as comparative standards, were measured simultaneously.

[0405] Table 2C. Composition of standard cationic protective varnishes that can be cured by UV-Vis with a mercury lamp (used to generate comparative standards ST1-ST4)

[0406] The standard cationic protective varnish described in Table 2C was applied to a reference polymer substrate (CCL Secure Guardian) using a manual coating unit (RK-print) with n°0 bar. TM A clear coat with dimensions of approximately 5 cm × 10 cm and a thickness of approximately 4 μm was formed on the surface. The clear coat was then exposed to UV-Vis light twice at a speed of 100 m / min under a mercury lamp unit (IST Metz GmbH; two lamps: an iron-doped mercury lamp + a mercury lamp) and cured under controlled relative humidity to generate comparative standards ST1-ST4.

[0407] After storage in the dark for 24 hours, the curing of each independent comparative standard ST1-ST4 was evaluated using the MEK friction test described in item A3 above. Comparative standards ST1-ST4 showed optimal curing.

[0408] Table 2D shows the absolute intensity (in photons / second) of the protective coatings obtained from varnishes E1-E5, C2, C4, C6, C8, and C9 under maximum fluorescence and the absolute intensity (in photons / second) of the corresponding comparative standards (ST1-ST4) under maximum fluorescence, as well as the ratio (relative fluorescence value) between the absolute intensity of each protective coating under maximum fluorescence and the absolute intensity (in photons / second) of the corresponding comparative standards ST1-ST4 under maximum fluorescence.

[0409] Table 2D. Fluorescence Measurement Results

[0410]

[0411] The fluorescence of the protective coatings obtained from the cationic UV-LED radiation-curable protective varnishes E1-E5 according to the invention and the comparative varnishes C2, C4, C6, C8, and C9 was also visually evaluated using a CAMAG UV Cabinet 4 (equipped with two UV tubes, each 8W, at 254 nm and 366 nm). Visual perception was correlated with the measured relative fluorescence values ​​determined as described above. Table 2E summarizes the correlation between visual perception and the measured relative fluorescence values.

[0412] Table 2E

[0413] Relative fluorescence values ​​@254 / 366nm Visual perception <1.3 Low fluorescence, close to the comparison standard 1.3–1.6 Acceptable fluorescence >1.6 Excessive fluorescence

[0414] Protective varnishes are typically applied to the entire surface and both sides of security documents. Therefore, protective coatings exhibiting a relative fluorescence higher than 1.6 (compared to comparative standards ST1-ST4) tend to make visual observation and / or machine readability of luminescent security features present in the security document difficult or even impossible. As demonstrated in experiments using protective varnishes E1-E5 according to the invention, cationic UV-LED curable protective varnishes containing a photosensitizer of general formula (I) and a 2-keto-thioxanthone moiety concentration of about 1.3 mmol to about 4.7 mmol / 100 g of protective varnish exhibited optimal curing performance and low to acceptable fluorescence at both 254 nm and 366 nm. Cationic UV-LED curable protective varnishes containing a photosensitizer of general formula (I), but with a 2-keto-thioxanthone moiety concentration lower than about 1.3 mmol / 100 g of protective varnish, such as comparative varnish C1, showed poor curing performance. Photosensitizers including those of general formula (I), but with a concentration of 2-keto-thioxanthone moiety higher than 4.7 mmol / 100g, can be cured by cationic UV-LED radiation of protective varnishes, for example, compared to varnish C2, which has good curing properties but produces a protective coating that exhibits excessive fluorescence.

[0415] As demonstrated in experiments with comparative varnishes C3, C5, and C7, varnishes containing small amounts of thioxanthone containing photosensitizers other than those of general formula (I) described herein exhibit poor curing performance and result in incomplete curing of coatings using curing conditions suitable for industrial coating methods.

[0416] As demonstrated in experiments using comparative varnishes C4, C6, and C8, the cationic UV-LED radiation-curable protective varnish exhibits good curing performance but produces a protective coating that displays excessive fluorescence (particularly at 254 nm). This protective varnish contains a reactive thioxanthone moiety containing a photosensitizer other than that of general formula (I), wherein the concentration of the reactive thioxanthone moiety is within the required protection range.

[0417] As demonstrated in experiments conducted with comparative varnish C9, cationic UV-LED radiation-curable protective varnishes containing strontium photoinitiator instead of diaryliodonium photoinitiator and 9,10-dibutoxyanthracene as a photosensitizer exhibit good curing performance but produce a protective coating that displays extremely high fluorescence.

[0418] Cationic UV-LED radiation-curable protective varnishes exhibiting excessive fluorescence, particularly relative fluorescence values ​​above approximately 1.6 as measured above, are unsuitable for use on security documents because they make the machine detectability of potential luminescent security features present on the security documents difficult or even impossible.

Claims

1. A cationic UV-LED radiation-curable protective varnish, comprising: a) 65% to 90% by weight of an alicyclic epoxide, or a mixture of an alicyclic epoxide with one or more cationic curable monomers other than the alicyclic epoxide; b) 1% to 10% by weight of diaryliodomonium salts; c) 0.01% to 5% by weight of nonionic surfactant; and d) Photosensitizers of general formula (I): (I) In general formula (I) A 1 and A 2 Each is independently selected from hydrogen and the following structural components: ； -L 1 -Selected from: , ,and ; -L 2 -Selected from: , ,and ; n1 and n2 are integers greater than or equal to 0; and or m represents 0; B represents hydrogen; C is selected from hydrogen, ,and ; A 3 and A 4 Each is independently selected from hydrogen and the following structural components: ； -L 3 -and-L 4 - Selected independently from: , ,and ; And n3 and n4 are integers greater than or equal to 0, where The sum of n1 + n2 is included between 2 and 8; The sum of n1 + n2 + n3 is included between 3 and 12; and The sum of n1+n2+n3+n4 is included in the range of 4-16; or m represents 1; B is selected from ethyl, and ; C is selected from , ,and ; A 3 A 4 A 5 and A 6 Each is independently selected from hydrogen and the following structural components: ； -L 3 -、-L 4 -、-L 5 -and-L 6 - Selected independently from: , ,and ; And n3, n4, n5, and n6 are integers greater than or equal to 0, where The sum of n1 + n2 + n3 is included in the range of 3-12; The sum of n1+n2+n3+n4 is included in the range of 4-16; The sum of n1+n2+n3+n4+n6 is included in the range of 5-15; The sum of n1+n2+n3+n5 is included in the range of 4-16; The sum of n1+n2+n3+n4+n5 is included in the range of 5-15; The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6-18; in The cationic UV-LED radiation-curable protective varnish includes a portion of the photosensitizer of general formula (I). The concentration is 1.3 mmol to 4.7 mmol per 100g of cationic UV-LED radiation-curable protective varnish; The weight percentage is based on the total weight of the cationic UV-LED radiation-curable protective varnish.

2. The cationic UV-LED radiation-curable protective varnish according to claim 1, wherein... -L 1 -express And -L 2 -、-L 3 -、-L 4 -、-L 5 -and-L 6 -express .

3. The cationic UV-LED radiation-curable protective varnish according to claim 1, wherein... -L 1 -express And -L 2 -、-L 3 -、-L 4 -、-L 5 -and-L 6 -express .

4. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has the general formula (Ia): (Ia) in A 1 A 2 C, n1, and n2 have the meanings defined in claim 1, and -L 1 -and-L 2 - It has the meaning defined by any one of claims 1-3.

5. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has the general formula (Ib): (Ib) in A 1 A 2 C, n1, and n2 have the meanings defined in claim 1, and -L 1 -and-L 2 - It has the meaning defined by any one of claims 1-3.

6. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has the general formula (Ic): (Ic) in A 1 A 2 A 5 C, n1, n2, and n5 have the meaning defined in claim 1, and -L 1 -、-L 2 -and-L 5 - It has the meaning defined by any one of claims 1-3.

7. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein... C indicates Where A 3 and n3 have the meaning defined in claim 1, and -L 3 - It has the meaning defined in any one of claims 1-3.

8. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein a portion of the cationic UV-LED-curable protective varnish... The concentration is 1.6 mmol to 2.9 mmol per 100g of cationic UV-LED curable protective varnish.

9. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the diaryliodonium salt has the general formula (II): (II) in R 1 -R 10 They are independently selected from hydrogen, C1-C 18 -alkyl and C1-C 12 -alkoxy; and An - It is selected from BF4 B(C6F5)4 PF6 AsF6 SbF6 CF3SO3 (CH3C6H4)SO3 (C4F9)SO3 (CF3)CO2 (C4F9)CO2 and (CF3SO2)3C Anions in the solution.

10. The cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein one or more cationic curable monomers other than the alicyclic epoxides are selected from: vinyl ethers, allyl ethers, cyclic ethers other than alicyclic epoxides, lactones, cyclic sulfides, vinyl sulfides, allyl sulfides, hydroxyl-containing compounds, and mixtures thereof.

11. The cationic UV-LED radiation curable protective varnish according to any one of claims 1-3, wherein the varnish is selected from flexographic printing varnish, inkjet printing varnish and screen printing varnish.

12. A method for coating a security document, the security document comprising a substrate and one or more security features applied to or inserted into a portion of the substrate, wherein the method comprises the following steps: i) Applying a cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3 to the surface of the substrate of the security document or the surface of one or more security features to form a varnish layer; and ii) The varnish layer is cured by exposure to UV light emitted by a UV-LED source to form a protective coating covering the surface of the substrate of the security document and / or the surface of one or more security features.

13. The method of claim 12, wherein the application is performed by a printing method selected from inkjet printing, flexographic printing and screen printing.

14. A method for coating a security document, the security document comprising a substrate and one or more security features applied to or inserted into a portion of the substrate, wherein the method comprises the following steps: i) Applying a cationic UV-LED radiation-curable protective varnish according to any one of claims 1-3 to the surface of the substrate of the security document and the surface of the one or more security features to form a varnish layer; and ii) The varnish layer is cured by exposure to UV light emitted by a UV-LED source to form a protective coating covering the surface of the substrate of the security document and / or the surface of one or more security features.

15. A security document comprising a substrate, one or more security features applied to or inserted into a portion of the substrate, and a protective coating covering a surface of the substrate or a surface of the one or more security features, wherein the protective coating is obtained by the method of claim 12.

16. A security document comprising a substrate, one or more security features applied to or inserted into a portion of the substrate, and a protective coating covering a surface of the substrate and a surface of the one or more security features, wherein the protective coating is obtained by the method of claim 12.

17. The secure document of claim 15 or 16, wherein the secure document is selected from banknotes, contracts, checks, vouchers, tax stamps, tax labels, agreements, passports, identity cards, visas, credit cards, and admission tickets.

18. The secure document according to claim 15 or 16, wherein the secure document is selected from tickets, identity documents, and transaction cards.

19. The security document according to claim 15 or 16, wherein the security document is selected from bank cards and passes.

Images