Security document with hybrid uv-led radiation curable protective varnish

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 hybrid UV-LED radiation curable protective varnish comprising: a) from about 60 wt-% to about 85 wt-% of a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide and one or more cationically curable monomers other than the cycloaliphatic epoxide; b) from about 3 wt-% to about 15 wt-% of one or more radically curable monomers and / or oligomers; c) from about 1 wt-% to about 6 wt-% of a diaryliodonium salt; d) from about 0.5 wt-% to about 3 wt-% of a radical photoinitiator selected from the group consisting of alpha-hydroxy ketones, alpha-alkoxy ketones, benzyl diketones, benzoin ethers, phosphine oxides, phenylglyoxalic acid esters, and mixtures thereof; e) from about 0.01 wt-% to about 5 wt-% of a non-ionic surfactant; and f) a photosensitizer of general formula (I), wherein the weight percentages are based on the total weight of the hybrid UV-LED radiation curable protective varnish.

Description

TECHNICAL FIELD

[0001] 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. BACKGROUND

[0002] With the continuous improvement in the quality of color copies and prints and the attempts to protect security documents such as banknotes, value documents or cards, transport tickets or cards, tax banderols and commodity labels from counterfeiting, tampering or illegal reproduction, it is a traditional practice to introduce various security features in these documents. Typical examples of security features include anti-counterfeiting security threads, windows, fibers, planchettes, foils, patches, labels, holograms, watermarks, security features obtained from security inks containing security materials such as magnetic pigments, UV absorbing pigments, IR absorbing pigments, optically variable pigments, polarizing pigments, luminescent pigments, electrically conductive pigments and surface-enhanced Raman spectroscopy particles.

[0003] It is well known to provide security documents, in particular banknotes, with a soil resistant protective coating to extend their lifetime and fitness for circulation. The protective coating is a protective layer facing the document environment, which is obtained from a heat (solvent containing) curable varnish, a radiation curable varnish or a combination thereof.

[0004] European patent application publication no. EP 0256170 Al proposes a protective layer consisting essentially of a cellulose ester or ether for coating currency paper printed with an ink containing 1 to 10 wt% of micronized wax. The protective layer is obtained by applying a solvent containing varnish on the surface of the currency paper by spraying, dipping or roll coating and curing the varnish with a hot air stream.

[0005] The increasing sensitivity of the public to environmental issues and the necessary response of the chemical industry to environmental regulations have prompted the industry to develop radiation curable protective varnishes (i.e. varnishes that cure by UV-visible light radiation or electron beam radiation) that contain no or significantly reduced amounts of organic solvents (volatile organic components, VOCs). In addition to being more environmentally friendly than solvent containing protective varnishes, radiation curable protective varnishes enable the manufacture of protective coatings with increased chemical and physical resistance and are conveniently cured, thereby reducing the manufacturing time of security documents coated with radiation curable protective varnishes.

[0006] Free radical UV radiation curable coatings suffer from insufficient adhesion properties, limited physical resistance and undesirably high levels of shrinkage during curing, which are cured through an activated free radical mechanism involving one or more free radical photoinitiators capable of releasing free radicals upon the action of radiation, in particular UV light, which in turn initiate the polymerization of free radical curable monomers and / or oligomers to form a cured layer. Cationic UV radiation curable coatings, which are cured through an activated cationic mechanism involving UV-Vis light of one or more cationic photoinitiators releasing cationic species such as acids, which in turn initiate the polymerization of cationic curable monomers, forming a cured adhesive, exhibit increased adhesion and mechanical resistance when compared to free radical UV radiation curable coatings. Hybrid UV radiation curable coatings, i.e. coatings containing both cationic curable monomers and free radical curable monomers and / or oligomers, exhibit adhesion and mechanical resistance comparable to cationic UV radiation curable coatings and, in addition, have the advantage of higher curing speed compared to cationic UV radiation curable coatings.

[0007] International patent application publication no. WO2014067715A1 has disclosed the use of a hybrid UV-Vis radiation curable protective varnish comprising cationic curable compounds, free radical curable compounds, cationic photoinitiators, free radical photoinitiators and fluorinated compounds for imparting dirt resistance to security documents. The hybrid UV-Vis radiation curable protective varnish described therein is applied by screen printing or flexographic printing and cured by exposure to UV light emitted by a standard mercury UV lamp.

[0008] Mercury lamps require a lot of energy, need an efficient and expensive heat dissipation system, are prone to form ozone and have a limited lifetime. In order to provide a solution that is less costly, requires less intervention and is more environmentally friendly, UV-LED based lamps and systems have been developed for curing inks and varnishes. In contrast to medium pressure mercury lamps having an emission band in the UV-A, UV-B and UV-C region of the electromagnetic spectrum, UV-LED lamps emit radiation in the UV-A region. Moreover, current UV-LED lamps emit quasi-monochromatic radiation, i.e. only one wavelength, for example 365 nm, 385 nm, 395 nm or 405 nm.

[0009] The UV-curing efficiency of a varnish or ink layer depends, inter alia, on the overlap of the emission spectrum of the radiation source used for the curing and the absorption spectrum of the photoinitiator contained in the varnish or ink. Thus, mixed UV-radiation curable coating or ink layers containing a mixture of conventionally used cationic and free radical photoinitiators suffer from reduced curing efficiency upon curing with UV-LED lamps as a result of the poor overlap of the emission spectrum of UV-LED lamps with the absorption of conventionally used photoinitiators, leading to slow or poor curing or curing defects.

[0010] Mixed UV-LED radiation curable compositions have been described in the literature. Said mixed UV-LED radiation curable compositions contain a free radical photoinitiator, a cationic photoinitiator and a photosensitizer which absorbs the energy of the light emitted by the UV-LED lamp and acts as a donor by transferring energy to the cationic photoinitiator. Chinese patent application publication CN107011768A discloses a mixed high stain resistance matte finish gloss oil which is curable by UV-LED exposure. The mixed high stain resistance matte finish gloss oil contains 60 wt-% of a cycloaliphatic epoxide, 18 wt-% of an oxetane, 5 wt-% of an aliphatic epoxy dimethacrylate, 3 wt-% of 4,4'-dimethyldiphenyliodonium hexafluorophosphate, 0.5 wt-% of 1-(diphenyl-4-yl)-2-methyl-2-morpholinopropan-1-one and 0.5 wt-% of 1-chloro-4-propyloxythioxanthone (CPTX). Due to the amount of CPTX sensitizer required for achieving good curing, in particular, and the photoinitiating system used in the mixed LED curable mixed high stain resistance matte finish gloss oil known in the art, the mixed UV-LED radiation curable compositions known in the art exhibit high fluorescence upon excitation with UV light, in particular upon excitation with UV light having a wavelength of 254 nm or 366 nm.

[0011] It is well known that UV light excitable luminescent security features have been widely used in the field of security documents, in particular for banknotes, to impart additional covert security features to said security documents, where the protection of said security documents against counterfeiting and illegal reproduction relies on the concept that such features generally require specialized equipment and knowledge to detect them. UV light excitable luminescent security features include for example UV light excitable luminescent fibers, UV light excitable luminescent security threads, UV light excitable luminescent labels, stripes or foils, where at least a portion of said labels, stripes or foils show luminescence when excited with UV light, and printed UV light excitable luminescent features. Said printed UV light excitable luminescent features include luminescent numbering (printed by letterpress), printed labels (printed by indirect letterpress) and luminescent features printed by offset. Since security documents usually contain UV light excitable luminescent security features, which are covered by a protective coating obtained from a protective varnish, photoinitiating systems known in the art cannot be used in protective varnishes for security documents, because the high level of fluorescence exhibited by the protective coating upon excitation with UV light of a wavelength of for example 254 nm or 366 nm impairs the machine detection and / or human recognition of the UV light excitable luminescent security features.

[0012] Therefore, there is still a need for a hybrid UV-LED radiation curable protective varnish for providing a protective coating for security documents at high speed, i.e. at industrial speed, which extends the lifetime and the circulation suitability of said security documents, wherein said hybrid UV-LED radiation curable varnish exhibits optimal curing performance and, after curing, exhibits a low fluorescence in response to 254 nm excitation and 366 nm excitation, which does not impair the machine detection and / or human recognition of luminescent security features contained by the coated security documents, which are excitable by UV light, in particular by UV light of a wavelength of for example 254 nm or 366 nm. SUMMARY

[0013] Therefore, it is an object of the present invention to provide a hybrid UV-LED radiation curable protective varnish for coating security documents at high speed, i.e. at industrial speed, to extend the lifetime and the circulation suitability of said security documents, wherein said hybrid UV-LED radiation curable varnish exhibits optimal curing performance and, after curing, exhibits a low fluorescence in response to excitation by UV light, for example 366 nm excitation and 254 nm excitation. This is achieved by the hybrid UV-LED radiation curable protective varnish as claimed herein, wherein said protective varnish comprises:

[0014] a) from about 60 wt-% to about 85 wt-% of a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide and one or more cationically curable monomers other than the cycloaliphatic epoxide;

[0015] b) from about 3 wt-% to about 15 wt-%, preferably from about 6 wt-% to about 10 wt-%, more preferably about 8 wt-%, of one or more free radical curable monomers and / or oligomers;

[0016] c) from about 1 wt-% to about 6 wt-%, preferably from about 2 wt-% to about 4 wt-%, more preferably about 2.5 wt-%, of a diaryliodonium salt;

[0017] d) from about 0.5 wt-% to about 3 wt-%, preferably from about 1 wt-% to about 2 wt-%, more preferably about 1.5 wt-%, of a free radical photoinitiator selected from the group consisting of a-hydroxy ketones, a-alkoxy ketones, benzyl diketones, benzoin ethers, phosphine oxides, phenyl glyoxalic acid esters, and mixtures thereof;

[0018] e) from about 0.01 wt-% to about 5 wt-% of a non-ionic surfactant; and

[0019] f) a photosensitizer of general formula (I)

[0020]

[0021] wherein in general formula (I)

[0022] or

[0023] i) A 1 and A 2 are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0024] -L 1 - is selected from the group consisting of

[0025]

[0026] -L 2 - is selected from the group consisting of

[0027]

[0028] n1 and n2 are integers greater than or equal to 0;

[0029] and

[0030] or

[0031] m represents 0;

[0032] B represents hydrogen;

[0033] C is selected from the group consisting of hydrogen,

[0034] A 3 and A 4are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0035]

[0036] - L 3 - and -L 4 - are independently of each other selected from the group consisting of

[0037]

[0038] and n3 and n4 are integers greater than or equal to 0, wherein

[0039] the sum of n1 + n2 is comprised between 2 and 8;

[0040] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0041] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0042] or

[0043] m represents 1 ;

[0044] B is selected from the group consisting of ethyl, and

[0045] C is selected from the group consisting of

[0046] A 3 , A 4 , A 5 and A 6 are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0047]

[0048] - L 3 -, -L 4 -, -L 5 - and -L 6 - are independently of each other selected from the group consisting of

[0049]

[0050] and n3, n4, n5 and n6 are integers greater than or equal to 0, wherein

[0051] the sum of n1 + n2 + n3 is comprised between 3 and 12;

[0052] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0053] the sum of n1 + n2 + n3 + n4 + n6 is comprised between 5 and 15;

[0054] the sum of n1 + n2 + n3 + n5 is comprised between 4 and 16;

[0055] the sum of n1 + n2 + n3 + n4 + n5 is comprised between 5 and 15;

[0056] the sum of n1 + n2 + n3 + n4 + n5 + n6 is comprised between 6 and 18;

[0057] wherein the UV-LED radiation curable protective varnish comprises a moiety present in the photoinitiator of general formula (I) at a concentration comprised between about 1.3 mmol and about 3.2 mmol of said moiety per 100 g of the mixed UV-LED radiation curable protective varnish;

[0058] or

[0059] ii) A 1 and A 2 are independently from each other selected from hydrogen and a moiety of the following structure

[0060]

[0061] -L 1 - is selected from

[0062]

[0063] -L 2 - is selected from

[0064]

[0065] n1 and n2 are integers greater than or equal to 0;

[0066] and

[0067] or

[0068] m represents 0;

[0069] B represents hydrogen;

[0070] C is selected from hydrogen,

[0071] A 3 and A 4 are independently from each other selected from hydrogen and a moiety of the following structure

[0072]

[0073] -L 3 - and -L 4 - are independently from each other selected from

[0074]

[0075] and n3 and n4 are integers greater than or equal to 0, wherein

[0076] the sum of n1 + n2 is comprised between 2 and 8;

[0077] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0078] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0079] or

[0080] m represents 1 ;

[0081] B is selected from ethyl, and

[0082] C is selected from

[0083] A 3 , A 4 , A 5 and A 6 are independently from each other selected from hydrogen and a moiety of structure:

[0084]

[0085] -L 3 -, -L 4 -, -L 5 - and -L 6 - are independently from each other selected from

[0086]

[0087] and n3, n4, n5 and n6 are integers greater than or equal to 0, wherein

[0088] the sum of n1 + n2 + n3 is comprised between 3 and 12;

[0089] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0090] the sum of n1 + n2 + n3 + n4 + n6 is comprised between 5 and 15;

[0091] the sum of n1 + n2 + n3 + n5 is comprised between 4 and 16;

[0092] the sum of n1 + n2 + n3 + n4 + n5 is comprised between 5 and 15;

[0093] the sum of n1 + n2 + n3 + n4 + n5 + n6 is comprised between 6 and 18;

[0094] wherein the UV-LED radiation curable protective varnish comprises a moiety present in the photoinitiator of general formula (I) at a concentration of about 1.3 mmol to about 2.6 mmol of the moiety per 100 g of the mixed UV-LED radiation curable protective varnish;

[0095] wherein the weight percentage is based on the total weight of the mixed UV-LED radiation curable protective varnish.

[0096] Preferably, the photoinitiator comprised by the mixed UV-LED radiation curable protective varnish according to the present application is a compound of general formula (I-b) or a compound of general formula (I-c)

[0097]

[0098] wherein A 1 , A 2 , C, n1, n2, -L 1 - and -L 2 have the meaning defined herein.

[0099]

[0100] wherein A 1 , A 2 , A 5 , C, n1, n2, n5, -L 1 -, -L 2 - and -L 5 have the meaning defined herein.

[0101] The mixed UV-LED radiation curable protective varnish claimed and described herein can be cured by exposure to UV light emitted by a UV-LED light source, preferably by exposure to UV light at 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. Accordingly, another aspect according to the present application relates to a method of coating a security document comprising a substrate and one or more security features applied on or inserted into a portion of the substrate, wherein the method comprises the steps of:

[0102] i) applying the mixed UV-LED radiation curable protective varnish claimed and described herein on the surface of the substrate of the security document and / or on the surface of the one or more security features, preferably by a printing method selected from flexographic printing, inkjet printing and screen printing, so as to form a varnish layer; and

[0103] ii) curing the varnish layer by exposure to UV light emitted by a UV-LED source so as to form a protective coating covering the surface of the substrate and / or the surface of the one or more security features of the security document. The coating method according to the present application is environmentally friendly and enables the manufacture of a dirt repellent protective coating for security documents in a convenient manner, i.e. at industrial speeds, which displays an acceptable level of fluorescence in response to excitation by UV light, e.g. 366 nm excitation and 254 nm excitation.

[0104] Another aspect according to the present application relates to a security document comprising a substrate, one or more security features applied on 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 of the security document, wherein the protective coating is obtained by the coating method as claimed and described herein. DETAILED DESCRIPTION

[0105] Definitions

[0106] The following definitions are used to clarify the meaning of terms discussed in the specification and recited in the claims.

[0107] As used herein, the indefinite article "a" or "an" means one as well as more than one and does not necessarily limit its designated noun to a single entity.

[0108] As used herein, the term "about" means that the amount or value in question can be the recited value or some other value within a range of ±5% of that value. In general, the term "about" when used in reference to a particular recited value is intended to mean within ±5% of that value. As an example, the phrase "about 100" means a range of 95 to 105. Preferably, the range indicated by the term "about" means within ±3%, more preferably ±1% of the value. Generally, when the term "about" is used, it is expected that similar results or effects according to the application can be obtained within ±5% of the recited value.

[0109] As used herein, the term "and / or" means that all the elements or only one of the elements can be present. For example, "A and / or B" means "A alone, or B alone, or both A and B." In the case of "A alone," the term also encompasses the possibility that B is not present, i.e., "A alone, but not B."

[0110] The term "comprising", as used herein, is intended to be non-exclusive and open-ended. Thus, for example, a solution comprising compound A can include other compounds in addition to A. However, the term "comprising" also encompasses the more restrictive meanings of "consisting essentially of and "consisting of" as specific embodiments thereof, so that, for example, a solution "comprising A, B, and optionally C" can also consist (essentially) of A and B or consist (essentially) of A, B, and C.

[0111] Where the specification refers to "preferred" embodiments / features, then so long as a particular combination of "preferred" embodiments / features is technically meaningful, whatever that meaning can be, then such combination of "preferred" embodiments / features is also deemed to be disclosed.

[0112] As used herein, the term "one or more" means one, two, three, four, etc.

[0113] The terms "UV-LED radiation curable", "UV-LED radiation cured", "UV-LED curable", and "UV-LED cured" mean radiation curing by photopolymerization under the influence of one or more radiations emitted by one or more UV-LED sources having wavelengths comprised between about 365 nm and about 405 nm, such as 365 nm and / or 385 nm and / or 395 nm.

[0114] As known to those skilled in the art and as used herein, hybrid varnish means a varnish containing both cationically curable monomers as well as both radically curable monomers and / or oligomers.

[0115] The term "hybrid UV-LED radiation curable varnish" means a varnish containing cationically curable monomers as well as both radically curable monomers and / or oligomers, which cures by both cationic and radical mechanisms activated by one or more radiations emitted by one or more UV-LED sources having wavelengths comprised between about 365 nm and about 405 nm, such as 365 nm and / or 385 nm and / or 395 nm.

[0116] As used herein, "2-keto-thioxanthone moiety" or "2-keto-9H-thioxanth-9-one" means a moiety having the following structure:

[0117]

[0118] As used herein, "1-chloro-4-carboxymethoxy-thioxanthone moiety" or "1-chloro-4-carboxymethoxy-9H-thioxanth-9-one" means a moiety having the following structure:

[0119]

[0120] Surprisingly, it has been found that a hybrid UV-LED radiation curable protective varnish comprises:

[0121] a) from about 60 wt-% to about 85 wt-% of a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide and one or more cationically curable monomers other than the cycloaliphatic epoxide;

[0122] b) from about 3 wt-% to about 15 wt-%, preferably from about 6 wt-% to about 10 wt-%, more preferably about 8 wt-%, of one or more free radical curable monomers and / or oligomers;

[0123] c) from about 1 wt-% to about 6 wt-%, preferably from about 2 wt-% to about 4 wt-%, more preferably about 2.5 wt-%, of a diaryliodonium salt;

[0124] d) from about 0.5 wt-% to about 3 wt-%, preferably from about 1 wt-% to about 2 wt-%, more preferably about 1.5 wt-%, of a free radical photoinitiator selected from the group consisting of a-hydroxy ketones, a-alkoxy ketones, benzyl diketones, benzoin ethers, phosphine oxides, phenyl glyoxalic acid esters, and mixtures thereof;

[0125] e) from about 0.01 wt-% to about 5 wt-% of a non-ionic surfactant; and

[0126] f) a photosensitizer of general formula (I)

[0127]

[0128] wherein in general formula (I)

[0129] or

[0130] i) A 1 and A 2 are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0131]

[0132] -L 1 - is selected from the group consisting of

[0133]

[0134] -L 2 - is selected from the group consisting of

[0135]

[0136] n1 and n2 are integers greater than or equal to 0;

[0137] and

[0138] or

[0139] m represents 0;

[0140] B represents hydrogen;

[0141] C is selected from the group consisting of hydrogen,

[0142] A 3 and A4 each independently of one another selected from the group consisting of hydrogen and a moiety of the structure:

[0143]

[0144] -L 3 - and -L 4 - each independently of one another selected from the group consisting of

[0145]

[0146] and n3 and n4 are integers greater than or equal to 0, wherein

[0147] the sum of n1 + n2 is comprised between 2 and 8;

[0148] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0149] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0150] or

[0151] m represents 1 ;

[0152] B is selected from the group consisting of ethyl, and

[0153] C is selected from the group consisting of

[0154] A 3 , A 4 , A 5 and A 6 each independently of one another selected from the group consisting of hydrogen and a moiety of the structure:

[0155]

[0156] -L 3 -, -L 4 -, -L 5 - and -L 6 - each independently of one another selected from the group consisting of

[0157]

[0158] and n3, n4, n5 and n6 are integers greater than or equal to 0, wherein

[0159] the sum of n1 + n2 + n3 is comprised between 3 and 12;

[0160] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0161] the sum of n1 + n2 + n3 + n4 + n6 is comprised between 5 and 15;

[0162] the sum of n1 + n2 + n3 + n5 is comprised between 4 and 16;

[0163] the sum of n1 + n2 + n3 + n4 + n5 is comprised between 5 and 15;

[0164] the sum of n1 + n2 + n3 + n4 + n5 + n6 is comprised between 6 and 18;

[0165] wherein the UV-LED radiation curable protective varnish comprises a moiety present in the photoinitiator of general formula (I) at a concentration of about 1.3 mmol to about 3.2 mmol of said moiety per 100 g of the mixed UV-LED radiation curable protective varnish;

[0166] or

[0167] ii) A 1 and A 2 are independently from each other selected from hydrogen and a moiety of the structure

[0168] -L 1 - is selected from

[0169]

[0170] -L 2 - is selected from

[0171]

[0172] n1 and n2 are integers greater than or equal to 0;

[0173] and

[0174] or

[0175] m represents 0;

[0176] B represents hydrogen;

[0177] C is selected from hydrogen,

[0178] A 3 and A 4 are independently from each other selected from hydrogen and a moiety of the structure

[0179]

[0180] -L 3 - and -L 4 - are independently from each other selected from

[0181]

[0182] and n3 and n4 are integers greater than or equal to 0, wherein

[0183] the sum of n1 + n2 is comprised between 2 and 8;

[0184] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0185] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0186] or

[0187] m represents 1 ;

[0188] B is selected from ethyl, and

[0189] C is selected from

[0190] A 3 , A 4 , A 5 and A 6 are independently from each other selected from hydrogen and moieties of the following structures:

[0191]

[0192] -L 3 -, -L 4 -, -L 5 - and -L 6 - are independently from each other selected from

[0193]

[0194] and n3, n4, n5 and n6 are integers greater than or equal to 0, wherein

[0195] the sum of n1 + n2 + n3 is comprised between 3 and 12;

[0196] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0197] the sum of n1 + n2 + n3 + n4 + n6 is comprised between 5 and 15;

[0198] the sum of n1 + n2 + n3 + n5 is comprised between 4 and 16;

[0199] the sum of n1 + n2 + n3 + n4 + n5 is comprised between 5 and 15;

[0200] the sum of n1 + n2 + n3 + n4 + n5 + n6 is comprised between 6 and 18;

[0201] Among them, the photoinitiator of general formula (I) of UV-LED radiation curable protective varnish contains a portion of the photoinitiator. The concentration of the component is approximately 1.3 mmol to approximately 2.6 mmol per 100 g of the mixed UV-LED radiation-curable protective varnish; wherein the weight percentage, based on the total weight of the mixed UV-LED radiation-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.

[0202] A photoinitiating system using a free radical photoinitiator selected from the group consisting of α-hydroxy ketones, α-alkoxy ketones, benzyl diketals, benzoin ethers, phosphine oxides, phenyl glyoxylates, and mixtures thereof, a diaryl iodonium salt as a cationic photoinitiator, and a photosensitizer of general formula (I) comprises

[0203] i) one or more 2-keto-thioxanthone moieties, wherein the concentration of the 2-keto-thioxanthone moieties present (comprising) in the photosensitizer of general formula (I) in the mixed UV-LED curable protective varnish is between about 1.3 mmol and about 3.2 mmol, preferably between about 1.45 mmol and about 3.10 mmol, more preferably between about 1.65 mmol and about 2.96 mmol of the 2-keto-thioxanthone moieties per 100 g of the mixed UV-LED curable protective varnish.

[0204] or,

[0205] ii) One or more 1-chloro-4-carboxymethoxy-thioxanthone moieties, wherein the concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moieties present (comprising) in the photosensitizer of general formula (I) is about 1.3 mmol to about 2.6 mmol, preferably about 1.45 mmol to about 2.45 mmol, more preferably about 1.66 mmol to about 2.31 mmol per 100 g of the mixed UV-LED curable protective varnish, ensuring that the mixed 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.

[0206] This document claims protection for and describes hybrid UV-LED radiation-curable protective varnishes including

[0207] f) Photosensitizers of general formula (I)

[0208]

[0209] In general formula (I)

[0210] or i) A 1 and A 2 are independently of each other selected from the group consisting of hydrogen and a moiety of the structure (i.e. a 2-keto-thioxanthone moiety);

[0211] -L 1 - is selected from the group consisting of

[0212]

[0213] -L 2 - is selected from the group consisting of

[0214]

[0215] n1 and n2 are integers greater than or equal to 0;

[0216] and

[0217] or

[0218] m represents 0;

[0219] B represents hydrogen;

[0220] C is selected from the group consisting of hydrogen,

[0221] A 3 and A 4 are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0222] (i.e. a 2-keto-thioxanthone moiety);

[0223] -L 3 - and -L 4 - are independently of each other selected from the group consisting of

[0224]

[0225] and n3 and n4 are integers greater than or equal to 0, wherein

[0226] the sum of n1 + n2 is comprised between 2 and 8;

[0227] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0228] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0229] or

[0230] m represents 1;

[0231] B is selected from the group consisting of ethyl,

[0232] C is selected from the group consisting of

[0233] A 3 A 4 A 5 and A 6 Each is independently selected from hydrogen and the following structural components:

[0234] (i.e., the 2-keto-thioxanthone moiety);

[0235] -L 3 -、-L 4 -、-L 5 -and-L 6 - Selected independently from each other

[0236]

[0237] And n3, n4, n5, and n6 are integers greater than or equal to 0, where

[0238] The sum of n1+n2+n3 is included in the range of 3 to 12;

[0239] The sum of n1+n2+n3+n4 is included in the range of 4 to 16;

[0240] The sum of n1+n2+n3+n4+n6 is included in the range of 5 to 15;

[0241] The sum of n1+n2+n3+n5 is included in the range of 4 to 16;

[0242] The sum of n1+n2+n3+n4+n5 is included in the range of 5 to 15;

[0243] The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6 to 18;

[0244] The UV-LED radiation-curable protective varnish includes the 2-keto-thioxanthone moiety present in the photosensitizer of general formula (I). The concentration of the mixture is such that per 100g of the mixed UV-LED radiation can cure the protective varnish of about 1.3mmol to about 3.2mmol, preferably about 1.45mmol to about 3.10mmol, more preferably about 1.65mmol to about 2.96mmol;

[0245] or

[0246] ii)A 1 and A 2 Selected independently from hydrogen and the following structural components (i.e., the 1-chloro-4-carboxymethoxy-thioxanthone moiety);

[0247] -L 1 - is selected from

[0248]

[0249] -L 2 - is selected from

[0250]

[0251] n1 and n2 are integers greater than or equal to 0;

[0252] and

[0253] or

[0254] m represents 0;

[0255] B represents hydrogen;

[0256] C is selected from hydrogen,

[0257] A 3 and A 4 are independently of each other selected from hydrogen and a moiety of the structure:

[0258] (i.e. a 1-chloro-4-carboxymethyloxy-thioxanthone moiety); -L 3 - and -L 4 - are independently of each other selected from

[0259]

[0260] and n3 and n4 are integers greater than or equal to 0, wherein

[0261] the sum of n1 + n2 is comprised between 2 and 8;

[0262] the sum of n1 + n2 + n3 is comprised between 3 and 12; and

[0263] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0264] or

[0265] m represents 1;

[0266] B is selected from ethyl,

[0267] C is selected from

[0268] A 3 , A 4 , A 5 and A 6are independently of each other selected from the group consisting of hydrogen and a moiety of the structure

[0269] (i.e. 1 -chloro-4-carboxymethoxy-thioxanthone moiety); -L 3 - and -L 4 - and -L 5 - and -L 6 - are independently of each other selected from the group consisting of

[0270]

[0271] and n3, n4, n5 and n6 are integers greater than or equal to 0, wherein

[0272] the sum of n1 + n2 + n3 is comprised between 3 and 12;

[0273] the sum of n1 + n2 + n3 + n4 is comprised between 4 and 16;

[0274] the sum of n1 + n2 + n3 + n4 + n6 is comprised between 5 and 15;

[0275] the sum of n1 + n2 + n3 + n5 is comprised between 4 and 16;

[0276] the sum of n1 + n2 + n3 + n4 + n5 is comprised between 5 and 15;

[0277] the sum of n1 + n2 + n3 + n4 + n5 + n6 is comprised between 6 and 18;

[0278] wherein the concentration of the 1 -chloro-4-carboxymethoxy-thioxanthone moiety present in the photoinitiator of general formula (I) in the mixed UV-LED radiation curable protective varnish is comprised between about 1.3 mmol and about 2.6 mmol, preferably between about 1.45 mmol and about 2.45 mmol, more preferably between about 1.66 mmol and about 2.31 mmol of said moiety per 100 g of the mixed UV-LED radiation curable protective varnish;

[0279] wherein the weight percentage is based on the total weight of the mixed UV-LED radiation curable protective varnish.

[0280] ​Since the hybrid UV-LED radiation curable protective varnish comprises either i) a concentration of 2-keto-thioxanthone moieties present in the photoinitiator of about 1.3 mmol to about 3.2 mmol, preferably of about 1.45 mmol to about 3.10 mmol, more preferably of about 1.65 mmol to about 2.96 mmol of said moieties per 100 g of the hybrid UV-LED radiation curable protective varnish, or ii) a concentration of 1-chloro-4-carboxymethoxy-thioxanthone moieties present in the photoinitiator of about 1.3 mmol to about 2.6 mmol, preferably of about 1.45 mmol to about 2.45 mmol, more preferably of about 1.66 mmol to about 2.31 mmol of said moieties per 100 g of the hybrid UV-LED radiation curable protective varnish, the respective amount of the photoinitiator of general formula (I) comprised by said varnish (wt-% based on the total weight of the hybrid UV-LED radiation curable protective varnish) can easily be calculated based on the molar concentration of the 2-keto-thioxanthone moieties in the photoinitiator of general formula (I) (2-keto-thioxanthone moieties (mmol) / photoinitiator of general formula (I) (g)), or based on the molar concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moieties in the photoinitiator of general formula (I) (1-chloro-4-carboxymethoxy-thioxanthone moieties (mmol) / photoinitiator of general formula (I) (g)). The molar concentration of the 2-keto-thioxanthone moieties in the photoinitiator of general formula (I) (2-keto-thioxanthone moieties (mmol) / photoinitiator (g)), and the molar concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moieties in the photoinitiator of general formula (I) (1-chloro-4-carboxymethoxy-thioxanthone moieties (mmol) / photoinitiator of general formula (I) (g)) are equal to the molar concentration of sulfur in said photoinitiator of general formula (I) (sulfur (mmol) / photoinitiator (g)), which can be determined by energy dispersive X-ray fluorescence (ED-XRF) using the signal of the sulfur atom comprised by the 2-keto-thioxanthone moieties and the 1-chloro-4-carboxymethoxy-thioxanthone moieties, respectively. The ED-XRF measurement can be performed by using 9H-thioxanthen-9-one (thioxanthone) containing a compound of known structure, e.g. 2-isopropyl-9H-thioxanthen-9-one (ITX), as internal standard, by the internal standard addition technique with the spectrometer Spectro XEFO S.

[0281] In a preferred embodiment according to the application, m denotes 0, B denotes hydrogen. Thus, preferred is a hybrid UV-LED curable protective varnish comprising a photoinitiator of general formula (I-a)

[0282]

[0283] wherein A 1 , A 2 , C, n1, n2, -L 1 - and -L2 - have the meaning as defined herein.

[0284] In an alternative preferred embodiment according to the application, m denotes 1. Thus, the mixed UV-LED radiation curable protective varnish as claimed and described herein can comprise a photosensitizer of the general formula (I-d)

[0285]

[0286] wherein A 1 , A 2 , B, C, -L 1 -, -L 2 -, n1 and n2 have the meaning as defined herein.

[0287] A particularly preferred embodiment according to the application relates to the mixed UV-LED radiation curable protective varnish as claimed and described herein, wherein m denotes 1 and B denotes ethyl. Thus, particularly preferred is the mixed UV-LED radiation curable protective varnish as claimed and described herein, which comprises a photosensitizer of the general formula (I-b)

[0288]

[0289] wherein A 1 , A 2 , C, n1, n2, -L 1 - and -L 2 - have the meaning as defined herein.

[0290] A further preferred embodiment according to the application relates to the mixed UV-LED radiation curable protective varnish as claimed and described herein, wherein m denotes 1 and

[0291] B denotes wherein -L 5 , n5 and A 5 have the meaning as defined herein. Thus, also preferred is the mixed UV-LED radiation curable protective varnish as claimed and described herein, which comprises a photosensitizer of the general formula (I-c)

[0292]

[0293] wherein A 1 , A 2 , A 5 , C, n1, n2, n5, -L 1 -, -L 2 - and -L 5 - have the meaning as defined herein.

[0294] Preferably, C denotes wherein -L 3 -, n3 and A 3 have the meaning defined herein. Thus, preferred are the mixed UV-LED radiation curable protective varnishes claimed and described herein comprising a photosensitizer of the general formula (I), (I-a), (I-b), (I-c) or (I-d), wherein C denotes and -L 3 -, n3 and A 3 have the meaning defined herein.

[0295] Particularly preferred are the mixed UV-LED radiation curable protective varnishes claimed and described herein comprising a photosensitizer of the general formula (I-e),

[0296]

[0297] wherein A 1 , A 2 , A 3 , -L 1 -, -L 2 -, -L 3 -, n1, n2 and n3 have the meaning defined herein.

[0298] Preferably, -L 1 denotes and -L 2 -, -L 3 -, -L 4 -, -L 5 - and -L 6 denotes Thus, preferred are the mixed UV-LED radiation curable protective varnishes comprising a photosensitizer of the general formula (I), (I-a), (I-b), (I-c), (I-d) or (I-e), wherein -L 1 denotes and -L 2 -, -L 3 -, -L 4 -, -L 5 - and -L 6 denotes

[0299] A particularly preferred embodiment according to the present application relates to a mixed UV-LED radiation curable protective varnish comprising a photosensitizer of the general formula (I-f)

[0300]

[0301] wherein A 1 , A 2 , A 3, n1, n2 and n3 have the meaning as defined herein. In general formula (I-f), A 1 , A 2 and A 3 one or more, preferably two or more, of which represent a 2-keto-thioxanthone moiety of the following structure:

[0302]

[0303] A particularly preferred hybrid UV-LED curable protective varnish according to the present application comprises a photoinitiator of general formula (I-f) wherein A 1 , A 2 and A 3 are 2-keto-thioxanthone moieties, and / or a photoinitiator of general formula (I-f) wherein A 1 and A 2 are 2-keto-thioxanthone moieties and A 3 represents hydrogen, and / or a photoinitiator of general formula (I-f) wherein A 1 is a 2-keto-thioxanthone moiety and A 2 and A 3 represent hydrogen, and characterized in that the concentration of the 2-keto-thioxanthone moieties is from about 1.3 mmol to about 3.2 mmol, preferably from about 1.45 mmol to about 3.10 mmol, more preferably from about 1.65 mmol to about 2.96 mmol of said moieties per 100 g of the hybrid UV-LED radiation curable protective varnish.

[0304] Also particularly preferred are the hybrid UV-LED radiation curable protective varnishes claimed and described herein, which comprise a photoinitiator of general formula (I-g)

[0305]

[0306] wherein A 1 , A 2 , A 3 , A 5 , -L 1 -, -L 2 -, -L 3 -, -L 5 -, n1, n2, n3 and n5 have the meaning as defined herein.

[0307] In a further preferred embodiment according to the present application, -L 1 represents and -L 2 -, -L 3 -, -L 4 -, -L 5 - and -L 6 - represents

[0308] Thus, also preferred are hybrid UV-LED curable protective varnishes comprising a photosensitizer of the general formula (I), (I-a), (I-b), (I-c), (I-d), (I-e) or (I-g), wherein -L 1 denotes

[0309] and -L 2 denotes 3 denotes 4 denotes 5 denotes 6 denotes

[0310] A particular preferred embodiment according to the present application relates to a hybrid UV-LED curable protective varnish comprising a photosensitizer of the general formula (I-h)

[0311]

[0312] wherein A 1 denotes 2 denotes 3 denotes 5 , n1, n2, n3 and n5 have the meaning as defined herein. In the general formula (I-h), one or more, preferably two or more of A 1 denotes 2 denotes 3 and A 5 denote a 1-chloro-4-carboxymethoxy-thioxanthone moiety of the following structure:

[0313]

[0314] A particular preferred hybrid UV-LED curable protective varnish according to the present application comprises a photosensitizer of the general formula (I-h) wherein A 1 denotes 2 denotes 3 and A 5 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety, and / or wherein A 1 denotes 2 and A 3 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A 5 denotes hydrogen, and / or wherein A 1 and A 2 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A 3 and A 5 denotes hydrogen, and / or wherein A 1is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A 2 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A 3 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A 5 is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A W is a 1-chloro-4-carboxymethoxy-thioxanthone moiety and A

[0315] The mixed UV-LED radiation curable protective varnish can comprise a mixture of photosensitizers of general formula (I), (I-a), (I-b), (I-c), (I-d), (I-e), (I-f) or (I-h) provided that the varnish comprises

[0316] i) a concentration of 2-keto-thioxanthone moiety of about 1.3 mmol to about 3.2 mmol, preferably about 1.45 mmol to about 3.10 mmol, more preferably about 1.66 mmol to about 2.96 mmol of said moiety per 100 g of the mixed UV-LED radiation curable protective varnish,

[0317] or

[0318] ii) a concentration of 1-chloro-4-carboxymethoxy-thioxanthone moiety of about 1.3 mmol to about 2.6 mmol, preferably about 1.45 mmol to about 2.45 mmol, more preferably about 1.66 mmol to about 2.31 mmol of said moiety per 100 g of the mixed UV-LED radiation curable protective varnish.

[0319] The photosensitizers of general formula (I), (I-a), (I-b), (I-c), (I-d), (I-e), (I-f), (I-h) and (I-g) preferably have a weight average molecular weight (M 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 using the following formula as the polystyrene equivalent weight-average molecular weight (PS eq M). W The average of three measurements of the same solution, with a 95% confidence level:

[0320]

[0321] 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, which is included with the device, is used as the software.

[0322] This document claims protection for and describes hybrid UV-LED curable protective varnishes including

[0323] c) about 1 wt% to about 6 wt%, preferably about 2 wt% to about 4 wt%, more preferably about 2.5 wt% of diaryliodomonium salts.

[0324] 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 Nr 47855-94-7), PF6 - (hexafluorophosphate, CAS Nr 16919-18-9), AsF6 - (hexafluoroarsenate, CAS Nr 16973-45-8), SbF6 - (hexafluoroantimonate, CAS Nr 17111-95-4), CF3SO3 - (trifluoromethylsulfonate, CAS Nr 37181-39-8), (CH3C6H4)SO3 - (4-methylphenylsulfonate, CAS Nr 16722-51-3), (C4F9)SO3 - (1,1,2,2,3,3,4,4,4-nonafluoro-1 -butanesulfonate, CAS Nr 45187-15-3), (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)methide, CAS Nr 130447-45-9).

[0325] The two aryl groups of the diaryliodonium cation moiety can each independently be substituted with one or more straight chain or branched alkyl groups (e.g., methyl, ethyl, isopropyl, isobutyl, tert-butyl, undecyl, dodecyl, tridecyl, tetradecyl, etc.) optionally substituted with one or more halogens and / or one or more hydroxyl groups; with one or more alkoxy groups optionally substituted with one or more halogens and / or one or more hydroxyl groups; with one or more nitro groups; with one or more halogens; with one or more hydroxyl groups; or combinations thereof. Examples of diaryliodonium cation moieties described herein include bis(4-dodecylphenyl)iodonium (CAS Nr 71786-69-1), bis[4-(1,1-dimethylethyl)phenyl]iodonium (CAS Nr 61267-44-5), (4-isopropylphenyl)(4-methylphenyl)iodonium (CAS Nr 178233-71-1), bis(4-methylphenyl)iodonium (CAS Nr 46449-56-3), (4-methylphenyl)[4-(2-methylpropyl)phenyl]iodonium (CAS Nr 344562-79-4), bis(2,4-dimethylphenyl)]iodonium (CAS Nr 78337-07-2), bis(3,4-dimethylphenyl)]iodonium (CAS Nr 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 Nr 94564-97-3), bis(4-hexylphenyl)iodonium (CAS Nr 249300-48-9), bis(4-decylphenyl)iodonium (CAS Nr 137141-44-7), (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 Nr 137141-41-4), bis(4-heptadecylphenyl)iodonium (CAS Nr 144095-91-0), bis(4-octadecylphenyl)iodonium (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 167997-65-1), (4-tridecylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-73-1), (4-tetradecylphenyl)(4-undecylphenyl)iodonium (CAS Nr 167997-79-7), (4-tetradecylphenyl)(4-tridecylphenyl)iodonium (CAS Nr 167997-75-3), p-(octyloxyphenyl)phenyl iodonium (CAS Nr 121239-74-5), [4-[(2-hydroxytetradecyl)oxy]phenyl]phenyl iodonium (CAS Nr 139301-14-7), phenyl[3-(trifluoromethyl)phenyl]iodonium (CAS Nr 789443-26-1), bis(4-fluorophenyl)iodonium (CAS Nr 91290-88-9), (4-nitrophenyl)phenyl iodonium (CAS Nr 46734-23-0), and (4-nitrophenyl)(2,4,6-trimethylphenyl)iodonium (CAS Nr 1146127-10-7).

[0326] Preferably, the diaryliodonium salt is a compound of general formula (II)

[0327]

[0328] wherein

[0329] R 1 -R 10 are independently of each other selected from hydrogen, Ci-C 18 -alkyl and Ci-C 12 -alkoxy; and

[0330] An - is an anion selected from the group consisting of BF4 - , B(C6F5)4 - , PF6 - , AsF6 - , SbF6 - , CF3SO3 - , (CH3C6H4)SO3 - , (C4F9)SO3 - , (CF3)CO2 - , (C4F9)CO2 - and (CF3SO2)3C - , preferably from the group consisting of BF4 - , B(C6F5)4 - , PF6 - , AsF6 - , SbF6 - and CF3SO3 - .

[0331] As used herein, the term "Ci-C 18 -alkyl" refers to saturated straight-chain or branched monovalent hydrocarbon radicals of 1 to 18 carbon atoms (Ci-C 18 ). Ci-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).

[0332] 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 to 12 carbon atoms (C1-C2) 12 (saturated straight-chain or branched monovalent hydrocarbon groups).

[0333] Preferably, in general formula (II), the substituent R1 , R 2 , R 4 , R 5 , R 6 , R 7 , R 9 and R 10 denote hydrogen. Preferred cationic photoinitiators are thus compounds of the general formula (II-a)

[0334]

[0335] wherein

[0336] An - has the meaning defined herein; and

[0337] R 3 and R 8 are independently of each other selected from the group consisting of hydrogen, Ci-C 18 -alkyl and Ci-C 12 -alkoxy, preferably from the group consisting of hydrogen and Ci-C 18 -alkyl, more preferably from the group consisting of hydrogen and Ci-C 12 -alkyl, especially preferably from the group of Ci-C4-alkyl, such as 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), 2-methyl-2-propyl (t-Bu, tert-butyl, -C(CH3)3).

[0338] Preferably, in the general formulae (II) and (II-a), the anion An - denotes PF6 - .

[0339] Particularly suitable diaryliodonium salts of the general formula (II) and (II-a) are commercially available under the names DEUTERON UV 1240 (CAS Nr 71786-70-4), DEUTERON UV 1242 (mixture of CAS Nr 71786-70-4 and CAS Nr 68609-97-2), DEUTERON UV 2257 (mixture of CAS Nr 60565-88-0 and CAS Nr 108-32-7), DEUTERON UV 1250 (branched bis-((C 10 -C 13) mixture of (4-methylphenyl)-iodonium hexafluoroantimonate and CAS Nr 68609-97-2), and DEUTERON UV 3100 (branched bis-((C7-C 10 ) mixture of (4-methylphenyl)-iodonium hexafluoroantimonate and CAS Nr 68609-97-2), and DEUTERON UV 3100 (branched bis-((C7-C

[0340] The hybrid UV-LED curable protective varnish according to the present application comprises:

[0341] a) from about 60 wt-% to about 85 wt-%, preferably from about 65 wt-% to about 80 wt-%, more preferably from about 70 wt-% to about 80 wt-% of a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more cationically curable monomers other than the cycloaliphatic epoxide.

[0342] Preferably, the hybrid UV-LED curable protective varnish claimed and described herein comprises from about 60 wt-% to about 85 wt-%, more preferably from about 65 wt-% to about 80 wt-%, particularly preferably from about 70 wt-% to about 80 wt-% of a mixture of a cycloaliphatic epoxide with one or more cationically curable monomers other than the cycloaliphatic epoxide. More preferably, the hybrid UV-LED curable protective varnish claimed and described herein comprising a mixture of a cycloaliphatic epoxide with one or more cationically curable monomers other than the cycloaliphatic epoxide comprises at least 60 wt-% of the cycloaliphatic epoxide, the weight percent being based on the total weight of the hybrid UV-LED radiation curable protective varnish.

[0343] For those skilled in the art, the cycloaliphatic epoxide is a cationically curable monomer containing at least a substituted or unsubstituted epoxycyclohexyl residue:

[0344] Preferably, the cycloaliphatic epoxide described herein comprises at least one cyclohexane ring and at least two epoxide groups. More preferably, the cycloaliphatic epoxide is a compound of general formula (III):

[0345]

[0346] wherein -L- represents a single bond or a divalent group comprising one or more atoms. The cycloaliphatic epoxide of general formula (III) is optionally substituted with one or more linear or branched alkyl groups containing 1 to 10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, hexyl, octyl, and decyl), preferably containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and isopropyl).

[0347] In general formula (III), the divalent group -L- can be a linear or branched alkylene group comprising 1 to 18 carbon atoms. Examples of the linear or branched alkylene group include, but are not limited to, methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene.

[0348] In general formula (III), the divalent group -L- can be a divalent cycloaliphatic 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.

[0349] In general formula (III), -L- can be a divalent group comprising one or more oxygen-containing linking groups, wherein the oxygen-containing linking group is selected from the group consisting of -C(=0)-, -OC(=0)0-, -C(=0)0-, and -0-. Preferably, the cycloaliphatic epoxide is a cycloaliphatic epoxide of general formula (III), wherein -L- is a divalent group comprising one or more oxygen-containing linking groups, wherein the oxygen-containing linking group is selected from the group consisting of -C(=0)-, -OC(=0)0-, -C(=0)0-, and -0-, more preferably a cycloaliphatic epoxide of general formula (III-a), (III-b), or (III-c) as defined below:

[0350]

[0351] wherein

[0352] L1may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 10 carbon atoms (e.g., methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, hexyl, octyl, and decyl), preferably containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and isopropyl).

[0353] L2may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 10 carbon atoms (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, hexyl, octyl, and decyl), preferably containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); and

[0354] l1and l2are integers, independent of each other, included between 0 and 9, preferably between 0 and 3, more preferably 0;

[0355]

[0356] wherein

[0357] L1may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl);

[0358] L2may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); and

[0359] l1and l2are integers, independent of each other, included between 0 and 9, preferably between 0 and 3, more preferably 0;

[0360] - L3- is a single bond or a linear or branched divalent hydrocarbon group containing 1 to 10 carbon atoms, preferably containing 3 to 8 carbon atoms, such as alkylene groups including trimethylene, tetramethylene, hexamethylene, and 2- ethylhexylene, and cycloalkylene groups such as 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene;

[0361]

[0362] wherein

[0363] L1may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl);

[0364] L2may be the same or different at each occurrence and is a linear or branched alkyl group containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); and

[0365] Ii and I2 are independently of each other an integer comprised between 0 and 9, preferably between 0 and 3, more preferably 0.

[0366] Preferred cycloaliphatic epoxides of general formula (III-a) include, but are not limited to: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (CAS Nr 2386-87-0), 3,4-epoxy-6-methyl-cyclohexyl-methyl-3,4-epoxy-6-methylcyclohexane carboxylate, 3,4-epoxy-2-methyl-cyclohexylmethyl-3,4-epoxy-2-methyl-cyclohexane carboxylate and 3,4-epoxy-4-methyl-cyclohexylmethyl-3,4-epoxy-4-methylcyclohexane carboxylate.

[0367] Preferred cycloaliphatic epoxides of general formula (III-b) include, but are not limited to: bis(3,4-epoxycyclohexylmethyl) adipate, bis(3,4-epoxy-6-methylcyclohexylmethyl) adipate, bis(3,4-epoxycyclohexylmethyl) oxalate, bis(3,4-epoxycyclohexylmethyl) pimelate and bis(3,4-epoxycyclohexylmethyl) sebacate.

[0368] Preferred cycloaliphatic epoxides of general formula (III-c) is 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-m-dioxane.

[0369] Other cycloaliphatic epoxides include cycloaliphatic epoxides of general formula (IV-a) and cycloaliphatic epoxides of general formula (IV-b) which are optionally substituted by one or more linear or branched alkyl groups containing 1 to 10 carbon atoms (e.g. methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, octyl and decyl), preferably containing 1 to 3 carbon atoms (e.g. methyl, ethyl, n-propyl and i-propyl):

[0370]

[0371] The cycloaliphatic epoxides described herein can 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) (Daicel Corp.) or TTA15 and TTA16 (TetraChem / Jiangsu).

[0372] The one or more cationically curable monomers other than the alicyclic epoxide described herein are selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers other than alicyclic epoxides (including epoxides other than alicyclic epoxides), oxetanes, and tetrahydrofurans, lactones, cyclic sulfides, vinyl sulfides, propenyl sulfides, hydroxyl-containing compounds, and mixtures thereof, preferably selected from the group consisting of vinyl ethers, cyclic ethers other than alicyclic epoxides, in particular oxetanes, and mixtures thereof.

[0373] Vinyl ethers are known in the art to accelerate curing and reduce tackiness, 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 increase its flexibility and adhesion to the substrate, which is particularly advantageous for coating plastics and polymeric substrates. Vinyl ethers also help to reduce the viscosity of the clear varnish while strongly copolymerizing with the clear varnish vehicle. Examples of preferred vinyl ethers for use in the hybrid UV-LED radiation curable protective clear varnish 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, t-butyl vinyl ether, t-amyl vinyl ether, cyclohexyl vinyl ether, cyclohexanedimethanol mono vinyl ether, cyclohexanedimethanol di vinyl ether, 4-(vinyloxy methyl)cyclohexyl methyl benzoate, phenyl vinyl ether, methylphenyl vinyl ether, methoxyphenyl vinyl ether, 2-chloroethyl vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 1,6-hexanediol mono vinyl ether, ethylene glycol di vinyl ether, ethylene glycol mono vinyl ether, 1,4-butanediol di vinyl ether, 1,6-hexanediol di vinyl ether, 4-(vinyloxy)butyl benzoate, bis[4-(vinyloxy)butyl]adipate, bis[4-(vinyloxy)butyl]succinate, bis[4-(vinyloxy methyl)cyclohexyl methyl]glutarate, 4-(vinyloxy)butyl stearate, trimethylolpropane tri vinyl ether, propylene carbonate propenyl ether, diethylene glycol mono vinyl ether, diethylene glycol di vinyl ether, ethylene glycol butyl vinyl ether, dipropylene glycol di vinyl ether, triethylene glycol di vinyl ether, triethylene glycol methyl vinyl ether, triethylene glycol mono butyl vinyl ether, tetraethylene glycol di vinyl ether, poly(tetrahydrofuran) di vinyl ether, polyethylene glycol-520 methyl vinyl ether, pluriol-E200 di vinyl ether, tris[4-(vinyloxy)butyl]trimellitate, 1,4-bis(2-vinyloxyethoxy)benzene, 2,2-bis(4-vinyloxyethoxyphenyl)propane, bis[4-(vinyloxy)methyl]cyclohexyl]methyl]terephthalate, bis[4-(vinyloxy)methyl]cyclohexyl]methyl]isophthalate. 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 can be hydroxyl-modified or (meth)acrylate-modified (e.g.: VEEA, 2-(2-vinyloxyethoxy)ethyl acrylate, from Nippon Shokubai (CAS: 86273-46-3)).

[0374] The use of epoxides other than alicyclic epoxides in the hybrid UV-LED radiation-curable protective varnishes claimed and described herein helps to accelerate curing and reduce tackiness, thereby reducing 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 by EMS Griltech under the trademark. (For example (V51-63 or RV 1806) for sale.

[0375] A preferred embodiment of the invention relates to a hybrid UV-LED radiation-curable protective varnish claimed and described herein, comprising:

[0376] a) A mixture of about 60 wt% to about 85 wt%, preferably about 65 wt% to about 80 wt%, more preferably about 70 wt% to about 80 wt% of an alicyclic epoxide and one or more oxetanes.

[0377] 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, but are not limited to, trimethyloxetane, 3,3-dimethyloxetane (CAS Nr 6921-35-3), 3-ethyloxetane-3-methanol (CAS Nr 3047-32-3), 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane (CAS Nr 298695-60-0), 3-ethyl-3-phenoxymethyloxetane (CAS Nr 3897-65-2), bis([1-ethyl(3-oxetane)]methyl) ether (CAS Nr 18934-00-4), 1,4-bis[3-ethyl-3-oxetanemethoxy)methyl]benzene (CAS Nr 142627-97-2), and 3,3-dimethyl-2(4-methoxy-phenyl)oxetane (CAS Nr 6921-35-3). 74267-45-1), 4,4-bis(3-ethyl-3-oxetane)methoxymethyl]biphenyl (CAS Nr 358365-48-7), and methyl methacrylate (3-ethyl-3-oxetane) (CAS Nr 37674-57-0). Preferred oxetanes are 3-ethyl-3-hydroxymethyloxetane (trade name Curalite from Perstorp). TM Ox sold), bis([1-ethyl(3-oxetane)]methyl) ether (by Perstorp under the trade name Curalite) TM OxPlus sells 3-ethyl-3-phenoxymethyloxetane (sold by Lambson under the trade name UviCure S140), 1,4-bis[3-ethyl-3-oxetanemethoxy]methyl]benzene (sold by Lambson under the trade name UviCure S150), 4,4-bis(3-ethyl-3-oxetane)methoxymethyl]biphenyl (sold by Lambson under the trade name UviCure S160), and methyl methacrylate (3-ethyl-3-oxetane) (sold by Lambson under the trade name UViCure S170).

[0378] This document claims protection for and describes hybrid UV-LED radiation-curable protective varnishes including

[0379] b) about 3 wt% to about 15 wt%, preferably about 6 wt% to about 10 wt%, more preferably about 8 wt% of one or more free radical curable monomers and / or oligomers.

[0380] The free radical curable monomers described herein are selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, and mixtures thereof, preferably selected from the group consisting of di(meth)acrylates, tri(meth)acrylates, and mixtures thereof.

[0381] The term "(meth)acrylate" in the context of the present invention refers to both acrylate and the corresponding methacrylate.

[0382] Preferred examples of mono(meth)acrylates include 2(2-ethoxyethoxy)ethyl (meth)acrylate, 2-phenoxyethyl (meth)acrylate, C12 / C14 alkyl (meth)acrylate, C16 / C18 alkyl (meth)acrylate, caprolactone (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, nonyl phenol (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, octyldecyl (meth)acrylate, tridecyl (meth)acrylate, methoxypoly(ethylene glycol) (meth)acrylate, polypropylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 1,3-butanediol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, alkoxylated di(meth)acrylate, ester glycol di(meth)acrylate, and mixtures thereof.

[0383] Preferred examples of di(meth)acrylates include bisphenol A di(meth)acrylates, alkoxylated (e.g., ethoxylated and propoxylated) bisphenol A di(meth)acrylates, bisphenol A diglycidyl ether di(meth)acrylates, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and mixtures thereof.

[0384] Preferred examples of tri(meth)acrylates include trimethylolpropane tri(meth)acrylates, alkoxylated (e.g., ethoxylated and propoxylated) trimethylolpropane tri(meth)acrylates, alkoxylated (e.g., ethoxylated and propoxylated) glyceryl tri(meth)acrylates, pentaerythritol tri(meth)acrylates, alkoxylated pentaerythritol tri(meth)acrylates, alkoxylated (e.g., ethoxylated and propoxylated) pentaerythritol tri(meth)acrylates, and mixtures thereof.

[0385] Preferred examples of tetra(meth)acrylates include di(trimethylolpropane)tetra(meth)acrylates, pentaerythritol tetra(meth)acrylates, alkoxylated (e.g., ethoxylated and propoxylated) pentaerythritol tetra(meth)acrylates, and mixtures thereof.

[0386] As used herein, the term "radical curable oligomer" refers to a free radical curable (meth)acrylate oligomer that can be branched or substantially linear and may have end groups and / or pendant (meth)acrylate functional groups. Preferably, the free radical curable oligomer is selected from the group consisting of (meth)acrylate oligomers, polyurethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof, more preferably from the group consisting of polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof.

[0387] Suitable examples of epoxy (meth)acrylate oligomers include, but are not limited to, aliphatic epoxy (meth)acrylate oligomers, particularly mono(meth)acrylates, di(meth)acrylates, and tri(meth)acrylates, as well as aromatic epoxy (meth)acrylate oligomers. Suitable examples of aromatic epoxy (meth)acrylate oligomers include bisphenol A (meth)acrylate oligomers such as bisphenol A mono(meth)acrylates, bisphenol A di(meth)acrylates, and bisphenol A tri(meth)acrylates, as well as alkoxylated (e.g., ethoxylated and propoxylated) bisphenol A (meth)acrylate oligomers such as alkoxylated bisphenol A mono(meth)acrylates, alkoxylated bisphenol A di(meth)acrylates, and alkoxylated bisphenol A tri(meth)acrylates, preferably ethoxylated bisphenol A di(meth)acrylates.

[0388] This document claims protection for and describes hybrid UV-LED radiation-curable protective varnishes, including:

[0389] d) about 0.5 wt% to about 3 wt%, preferably about 1 wt% to about 2 wt%, more preferably about 1.5 wt% of a free radical photoinitiator, said free radical photoinitiator being selected from the group consisting of α-hydroxy ketones, α-alkoxy ketones, benzyl diketals, benzoin ethers, phosphine oxides, phenyl glyoxylates, and mixtures thereof.

[0390] The free radical photoinitiators used in the mixed UV-LED radiation-curable protective varnishes claimed and described herein are selected from the group consisting of α-hydroxy ketones, α-alkoxy ketones, benzyl diketals, benzoin ethers, phosphine oxides, phenyl glyoxylates, and mixtures thereof.

[0391] Suitable α-hydroxy ketones include, without limitation, 2-hydroxy-4'- hydroxyethoxy-2-methylpropiophenone (CAS Nr 106797-53-9), 1 -hydroxycyclohexyl phenyl ketone (CAS Nr 947-19-3), 2-hydroxy-2-methyl-1 -phenylpropan-1 -one (CAS Nr 7473-98-5), 2-hydroxy-2-methyl-1 -(4-tert-butyl)phenylpropan-1 -one (CAS Nr 68400-54-4), 2-hydroxy-1 -[4-[[4-(2-hydroxy-2-methylpropanoyl)phenyl]methyl]phenyl]-2- methylpropan-1 -one (CAS Nr 474510-57-1 ), 2-hydroxy-1 -[4-[4-(2-hydroxy-2- methylpropanoyl)phenoxy]phenyl]-2-methylpropan-1 -one (CAS Nr 71868-15-0), 2- hydroxy-1 -[1 -[4-(2-hydroxy-2-methylpropanoyl)phenyl]-1,3,3-trimethylindan-5-yl]-2- methylpropan-1 -one (CAS Nr 135452-43-6), poly(oxy-1,2-ethanediyl), α-(1,1 -dimethyl- 2-oxo-2-phenylethyl)-ω-hydroxy- (CAS Nr 554449-21 -7), and oligo[2-hydroxy-2- methyl-1 -[4-(1 -methylethenyl)phenyl]propanone] (CAS Nr 163702-01 -0).

[0392] Suitable benzyl diketones include, without limitation, 2,2-dimethoxy-2- phenylacetophenone (CAS Nr 24650-42-8) and 2,2-diethoxy-1 -phenyl-1 - ethanone (CAS Nr 6175-45-7).

[0393] Suitable phenyl glyoxylic acid esters include, without limitation, methyl 2-oxo-2- phenylacetate (methyl benzoylformate, CAS Nr 15206-55-0), 2-[2-oxo-2-phenyl- acetyloxy-ethoxy]ethyl 2-oxo-2-phenylacetate (CAS Nr 211510-16-6), α-(2-oxo-2- phenylacetyl)-ω-[(2-oxo-2-phenylacetyl)oxy]-poly(oxy-1,4-butanediyl) (CAS Nr 1313205-82-1 ), and 2-(2-hydroxyethoxy)ethyl 2-oxo-2-phenylacetate (CAS Nr 442536-99-4).

[0394] Suitable benzoin ethers include, without limitation, 2-ethoxy-1,2-diphenyl- ethanone (CAS Nr 574-09-4), 2-isopropoxy-1,2-diphenyl-ethanone (CAS Nr 6652-28-4), 2-isobutoxy-1,2-diphenyl-ethanone (CAS Nr 22499-12-3), and 2-butoxy-1,2- diphenyl-ethanone (CAS Nr 22499-1 1 -2).

[0395] Suitable phosphine oxides include, without limitation, 2,3,6-trimethylbenzoyl diphenylphosphine oxide (CAS Nr 144865-32-7), 2,4,6-trimethylbenzoyl diphenylphosphine oxide (CAS Nr 75980-60-8), ethyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 84434-1 1 -7), phenyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 1539267-56-5), phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS Nr 162881 -26-7), bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (CAS Nr 145052-34-2), and oligomeric phosphine oxides, such as poly(oxy-1,2-ethanediyl), a,a',a"-1,2,3-propanetriyl tris[ω-[[phenyl(2,4,6-trimethylbenzoyl)phosphinoyl]oxy]-(CAS Nr 1834525-17-5) and poly(oxy-1,2-ethanediyl), a-[bis(2,4,6-trimethylbenzoyl)phosphinoyl]-ω-methoxy- (CAS Nr 1613725-81 -7).

[0396] The hybrid UV-LED radiation curable protective varnish claimed and described herein can comprise a mixture of the above radical photoinitiators.Such mixtures include, for example, mixtures of 2,4,6-trimethylbenzoyl diphenylphosphine oxide (CAS Nr 75980-60-8) and 2-hydroxy-2-methyl-1-phenylpropan-1-one (CAS Nr 7473-98-5), for example sold under the trade name Omnirad 4265 by IGM Resins; mixtures of phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS Nr 162881-26-7), ethyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 84434-11-7) and 2-hydroxy-2-methylpropiophenone (CAS Nr 7473-98-5), for example sold under the trade name Omnirad 2022 by IGM Resins; mixtures of ethyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 84434-11-7) and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (CAS Nr 162881-26-7), for example sold under the trade name Omnirad 2100 by IGM Resins; mixtures of 2-hydroxy-2-methylpropiophenone (CAS Nr 7473-98-5) and 1-hydroxycyclohexyl phenyl ketone (CAS Nr 947-19-3), for example sold under the trade name Omnirad 1000 by IGM Resins; mixtures of oligo[2-hydroxy-2-methyl-1-[4-(1-methylethenyl)phenyl]propanone] (CAS Nr 163702-01-0) and 2-hydroxy-2-methylpropiophenone (CAS Nr 7473-98-5), for example sold under the trade name Esacure KIP 100 F by IGM Resins; mixtures of 2-hydroxy-2-methylpropiophenone (CAS Nr 7473-98-5), ethyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 84434-11-7) and oligo[2-hydroxy-2-methyl-1-[4-(1-methylethenyl)phenyl]propanone] (CAS Nr 163702-01-0), for example sold under the trade name Omnirad BL 723 by IGM Resins; and mixtures of 2-hydroxy-2-methylpropiophenone (CAS Nr 7473-98-5), oligo[2-hydroxy-2-methyl-1-[4-(1-methylethenyl)phenyl]propanone] (CAS Nr 163702-01-0), ethyl (2,4,6-trimethylbenzoyl)phenylphosphonate (CAS Nr 84434-11-7) and 2,2-dimethoxy-1,2-diphenylethan-1-one (CAS Nr 24650-42-8), for example sold under the trade name Omnirad BL 724 by IGM Resins.

[0397] Preferably, the radical photoinitiator is selected from the group consisting of a-hydroxy ketones, benzyl diketones, phenyl glyoxalates and mixtures thereof, and more preferably selected from the group consisting of 2-hydroxy-4'-hydroxyethoxy-2-methylpropiophenone (CAS Nr 106797-53-9), 1 -hydroxycyclohexyl phenyl ketone (CAS Nr 947-19-3), benzoylformic acid methyl ester (CAS Nr 15206-55-0), 2,2-dimethoxy-1,2-diphenyl ethan-1 -one (CAS Nr 24650-42-8) and mixtures thereof.

[0398] The hybrid UV-LED radiation curable protective varnish claimed and described herein comprises

[0399] e) from about 0.01 wt-% to about 5 wt-%, preferably from about 0.05 wt-% to about 3 wt-%, more preferably from about 0.1 wt-% to about 2 wt-%, even more preferably from about 0.2 wt-% to about 1 wt-% of a non-ionic surfactant.

[0400] As it is well known to the person skilled in the art, non-ionic surfactants comprise a hydrophilic part and a hydrophobic part and are not charged. Preferably, the non-ionic surfactant used in the hybrid UV-LED curable protective varnish claimed and described herein has a molecular weight comprised between about 200 g / mol and about 3000 g / mol and / or comprises one or more functional groups selected from the group consisting of hydroxyl and epoxy groups. More preferably, the non-ionic surfactant is selected from the group consisting of non-ionic fluorinated surfactants and non-ionic silicone surfactants.

[0401] As used herein, the term "non-ionic fluorinated surfactant" includes non-ionic perfluoropolyether surfactants and non-ionic fluorosurfactants.

[0402] As used herein, the term "non-ionic fluorinated surfactant" includes non-ionic perfluoropolyether surfactants and non-ionic fluorosurfactants. n) below about 2000 [g / mol]. As used herein, perfluoropolyether backbone denotes a residue of a perfluoropolyether polymer comprising randomly distributed repeating units selected from perfluoromethylenyloxy (-CF2O-) and perfluoroethylenyloxy (-CF2-CF2O-). The perfluoropolyether residue is attached to the terminal functional group directly or via a spacer selected from methylene (oxyethylene), 1,1-difluoroethylidene- (oxyethylene), methylene-di(oxyethylene), 1,1-difluoroethylidene-di(oxyethylene), methylene-tri(oxyethylene), 1,1-difluoroethylidene-tri(oxyethylene), methylene-tetra(oxyethylene), 1,1-difluoroethylidene-tetra(oxyethylene), methylene-penta(oxyethylene), 1,1-difluoroethylidene-penta(oxyethylene), and linear or branched hydrocarbon groups, optionally fluorinated at the carbon atom connecting the spacer to the perfluoropolyether residue, comprising one or more urethane groups, or one or more amide groups, and optionally one or more cyclic moieties, including saturated cyclic moieties (such as cyclohexylidene) and aromatic cyclic moieties (such as phenylene). Preferably, the non-ionic perfluoropolyether surfactant is functionalized with one or more hydroxyl and / or epoxide functional groups.

[0403] Preferably, the non-ionic perfluoropolyether surfactant is a compound of general formula (V) having an average molecular weight (M n ) of about 1200 [g / mol] to about 2000 [g / mol]

[0404]

[0405] wherein

[0406] f and e are integers, independently of each other, selected from 1, 2 and 3;

[0407] FG 1 and FG 2 are terminal functional groups, independently of each other, selected from the group consisting of:

[0408] -OH, -OC(O)CH=CH2, -OC(O)C(CH3)=CH2, and -Si(OR 20 )3;

[0409] R 20 is C1-C4 alkyl;

[0410] -S 1 - represents a single bond or a spacer selected from:

[0411]

[0412] wherein

[0413] -J 1 - is selected from

[0414]

[0415]

[0416] wherein

[0417] j 1 is an integer comprised between 1 and 12, preferably between 4 and 10;

[0418] L5, which can be identical or different at each occurrence, is a linear or branched alkyl group containing from 1 to 10 carbon atoms (such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, octyl and decyl), preferably containing from 1 to 3 carbon atoms (such as methyl, ethyl, n-propyl and i-propyl);

[0419] L6, which can be identical or different at each occurrence, is a linear or branched alkyl group containing from 1 to 10 carbon atoms (such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, octyl and decyl), preferably containing from 1 to 3 carbon atoms (such as methyl, ethyl, n-propyl and i-propyl);

[0420] l5and l6are integers, independent from each other, comprised between 0 and 4, preferably between 0 and 1 ; and

[0421] -J 3 - is selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-;

[0422] -J 2 - is selected from

[0423]

[0424] a is an integer comprised between 1 and 6, preferably between 1 and 3; and

[0425] b is an integer comprised between 1 and 6, preferably between 2 and 4;

[0426] -S 2 - represents a single bond or a spacer selected from

[0427]

[0428]

[0429] wherein

[0430] -J 4 - is selected from

[0431]

[0432] wherein

[0433] j 4 is an integer comprised between 1 and 12, preferably between 4 and 10;

[0434] L7, which can be identical or different at each occurrence, is a linear or branched alkyl group containing from 1 to 10 carbon atoms (such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, octyl and decyl), preferably containing from 1 to 3 carbon atoms (such as methyl, ethyl, n-propyl and i-propyl);

[0435] L8, which can be identical or different at each occurrence, is a linear or branched alkyl group containing from 1 to 10 carbon atoms (such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, hexyl, octyl and decyl), preferably containing from 1 to 3 carbon atoms (such as methyl, ethyl, n-propyl and i-propyl);

[0436] l7and l8are integers, independent from each other, comprised between 0 and 4, preferably between 0 and 1 ; and

[0437] -J 6 - is selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-;

[0438] -J 5 - is selected from

[0439]

[0440] wherein

[0441] r is an integer comprised between 1 and 6, preferably between 1 and 3; and

[0442] w is an integer comprised between 1 and 6, preferably between 2 and 4;

[0443] and

[0444] wherein s and t are integers chosen such that the average molecular weight (M n ) of the compound of general formula (V) is comprised between about 1200 [g / mol] and about 2000 [g / mol].

[0445] Preferably, in general formula (V), FG 1 and FG 2 independently from each other represent -OC(O)CH=CH2, or -OC(O)C(CH3)=CH2;

[0446] -S 1 denotes wherein b has the meaning defined herein; and

[0447] -S 2 denotes wherein w has the meaning defined herein.

[0448] More preferably, in general formula (V), FG 1 and FG 2 denotes -OH;

[0449] -S 1 denotes a single bond or wherein a has the meaning defined herein;

[0450] -S 2 denotes a single bond or wherein r has the meaning defined herein; and the sum of o and r is comprised between 3 and 9.

[0451] Also preferably, in general formula (V), FG 1 and FG 2 denotes -Si(OR 20 )3;

[0452] R 20 is C1-C4 alkyl, preferably ethyl;

[0453] -S 1 denotes wherein b has the meaning defined herein; and

[0454] -S 2 denotes wherein w has the meaning defined herein. Preferred perfluoropolyether surfactants are thus compounds of general formula (V-a):

[0455]

[0456] wherein

[0457] b and w are integers comprised between 1 and 6, preferably between 2 and 4;

[0458] s is an integer between 2 and 6; and

[0459] q is an integer between 2 and 4.

[0460] Particularly suitable examples of non-ionic perfluoropolyether surfactants are the products sold under the name E10H, MD700, MD500, AD 1700, E-series and S10 are commercially available.

[0461] As used herein, the term "non-ionic fluorosurfactant" refers to a non-ionic surfactant containing a perfluoroalkyl chain CF3(CF2) x wherein x is an integer from 2 to 18. Preferably, the non-ionic fluorosurfactant is characterized by an average molecular weight (M n ) of from about 200 [g / mol] to about 2000 [g / mol].

[0462] Preferably, the non-ionic fluorosurfactant is a compound of general formula (VI):

[0463] CF3(CF2) x (CH2) y E

[0464] (VI)

[0465] wherein

[0466] x is an integer from 2 to 18;

[0467] y is an integer from 0 to 8; and

[0468] E is selected from

[0469]

[0470] -(CR2CR2O) z H, and -OSi(OR 20 )3,

[0471] wherein z is an integer from 0 to 15;

[0472] R can be the same or different at each occurrence and is selected from the group consisting of hydrogen and methyl; and

[0473] R 20 is C1-C4 alkyl, preferably R in general formula (VI) represents hydrogen.

[0474] Particularly preferred is a non-ionic fluorosurfactant of general formula (VI-a):

[0475] CF3(CF2) x (CH2) y (CR2CR2O) z H (VI-a)

[0476] wherein

[0477] x is an integer from 2 to 18;

[0478] y is an integer from 0 to 8;

[0479] z is an integer from 0 to 15; and

[0480] R can be the same or different at each occurrence and is selected from the group consisting of hydrogen and methyl, preferably hydrogen. Non-ionic fluorosurfactants of general formula (VI-a) are commercially available under the name CHEMGUARD S550-100 or CHEMGUARD S550, CHEMGUARD S222N, CHEMGUARD S559-100 or CHEMGUARD S559 (all sold by CHEMGUARD); Capstone™ FS-31, Capstone™ FS-35, Capstone™ FS-34, Capstone™ FS-30, Capstone™ FS-3100 (all sold by Chemours).

[0481] Also preferred are non-ionic fluorosurfactants of general formula (VI-b):

[0482] CF3(CF2) x (CH2) y OSi(OR 20 )3 (VI-b),

[0483] wherein

[0484] x is an integer from 2 to 18;

[0485] y is an integer from 0 to 8; and

[0486] R 20 is C1-C4 alkyl. Non-ionic fluorosurfactants of general formula (VI-b) are commercially available under the name Dynasylan F8261 and Dynasylan F8263 (sold by Evonik).

[0487] Also preferred are non-ionic fluorosurfactants of general formula (VI-c):

[0488]

[0489] wherein

[0490] x is an integer from 2 to 18;

[0491] y is an integer from 0 to 8; and

[0492] R 21selected from the group consisting of hydrogen and methyl. Examples of non-ionic fluorosurfactants of general formula (VI-c) include, but are not limited to: 1H,1H,2H,2H- perfluoro-octyl acrylate (Sigma-Aldrich), 1H,1H,2H,2H-perfluoro-octyl methacrylate (Sigma-Aldrich), 1H,1H-perfluoro-octyl acrylate (Sigma-Aldrich), 1H,1H- perfluoro-octyl methacrylate (Sigma-Aldrich), 1H,1H-perfluoro-heptyl acrylate (Sigma-Aldrich), and 1H,1H-perfluoro-heptyl methacrylate (Sigma-Aldrich).

[0493] As used herein, non-ionic silicone surfactant refers to a non-ionic surfactant comprising a silicone backbone containing randomly distributed repeating units selected from the group consisting of di(methyl)siloxane (— (CH3)2SiO— ) and / or methyl-(C2-C 10 — alkyl)-siloxane (— (CH3)(C2-C 10 — alkyl)SiO— ), wherein one or more methyl and / or C2-C 10 — alkyl groups can independently from each other be substituted with aryl, polyester, optionally a terminal functional group selected from the group consisting of hydroxyl, epoxide and (meth)acrylate, polyether, such as polyalkylene glycol (including polyethylene glycol and polypropylene glycol), optionally a terminal functional group selected from the group consisting of hydroxyl, epoxide and (meth)acrylate, hydroxyl, epoxide group or (meth)acrylate group, and / or wherein the silicone backbone can be attached to a terminal functional group selected from the group consisting of hydroxyl, epoxide group and (meth)acrylate group, directly or via a spacer. The silicone backbone described herein can be attached to an aliphatic polyurethane acrylate or fluorine-containing aliphatic polyurethane acrylate. Preferably, the non-ionic silicone surfactant is characterized by an average molecular weight below about 3000 [g / mol].

[0494] Non-ionic silicone surfactants include, but are not limited to, polyalkylmethylsiloxanes such as BYK-077 and BYK-085 sold by BYK, polyester-modified polydimethylsiloxanes such as BYK 310 sold by BYK, polyether-modified polydimethylsiloxanes such as BYK-330, BYK-377, BYK-333, BYK-345, BYK-346 and BYK-348 sold by BYK, polyester-modified polyalkylmethylsiloxanes such as BYK-315 sold by BYK, polyether-modified polyalkylmethylsiloxanes such as BYK-341, BYK-320 and BYK-325 sold by BYK, hydroxy-functionalized polydimethylsiloxanes such as HSI-2311, polyester-modified hydroxy-functional polydimethylsiloxanes, such as BYK-370 and BYK-373 sold by BYK, polyether-modified hydroxy-functional polydimethylsiloxanes, such as BYK-308 sold by BYK, polyether polyester-modified hydroxy-functional polydimethylsiloxanes, such as BYK-375 sold by BYK, epoxy-functional polydimethylsiloxanes, such as TEGO® G-1650 sold by Evonik, and mixtures thereof. E-Si 2330, acryloyloxy-functional polydimethylsiloxanes, such as TEGO® E-Si 2330 sold by Evonik, and mixtures thereof. V-SI 2250 and Rad 2700, polyester-modified acryl-functional polydimethylsiloxanes, such as BYK-371 sold by BYK, polyether-modified acryl-functional polydimethylsiloxanes, such as TEGO® Rad 2100 sold by Evonik, and mixtures thereof. 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, and mixtures thereof.

[0495] To facilitate the storage, stacking, and gripping of security documents, in particular the storage, stacking, and gripping of banknotes, the hybrid UV-LED radiation curable protective varnish claimed and described herein can comprise a matting agent that provides a matte protective coating with better gripping. In addition, the matte protective coating has the advantage of preserving the user's usual perception of the security document by touch, and causes much less reflection than a shiny protective coating, thus enabling the machine inspection and authentication of the security document with optical sensors habitually used. The matting agent can be present in an amount of about 1 wt-% to about 12 wt-%, weight percent (wt-%) based on the total weight of the hybrid UV-LED radiation curable protective varnish.

[0496] As is well known to those skilled in the art, matting agents should be avoided in hybrid 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 hybrid 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 hybrid UV-LED radiation-curable protective varnish can be applied directly to the surface of security features present in the security document. Furthermore, as described in International Patent Application Publication No. WO2011120917A1, this matting agent-free hybrid 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.

[0497] 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.

[0498] 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.

[0499] The preferred feature of a matting agent is that D, determined by laser diffraction, is... 50 The value is in the range of about 1 μm to about 25 μm, preferably from about 2 μm to about 15 μm, and more preferably between about 3 μm and about 10 μm.

[0500] 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, TS 100), PPG (available from PPG) (e.g., PPG 66, 2023, 8100, 8300), (available from PQ Corporation) (e.g. UV55C, UV70C, HP210, HP240, HP380, HP860) are commercially available.

[0501] The hybrid UV-LED radiation curable protective varnish can comprise up to 10 wt-% of an organic solvent, the weight percentage being based on the total weight of the hybrid UV-LED radiation curable protective varnish. Preferably, the organic solvent is present in an amount of about 1 wt-% to about 7.5 wt-%, more preferably about 2 wt-% to about 5 wt-%. Preferably, the organic solvent is a polar organic solvent selected from the group consisting of alcohols, glycols, glycol ethers, glycol esters, and cyclic carbonates, preferably having a boiling point higher than about 80 °C, more preferably higher than about 100 °C.

[0502] The hybrid UV-LED radiation curable protective varnish claimed and described herein can further comprise one or more additives including, but not limited to, antifoaming agents, defoaming agents, UV absorbers, anti-settling stabilizers, antimicrobial agents (including antibacterial agents, antiviral agents, antifungal agents), and combinations thereof.

[0503] The hybrid 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 cationically curable monomers other than the alicyclic epoxide with one or more radically curable monomers and / or oligomers, an organic solvent (when present), one or more additives (when present), an opacifier (when present), a non-ionic surfactant, a photoinitiator of general formula (I), a diaryliodonium salt, and a radical photoinitiator. Preferably, the solid ingredients of the hybrid UV-LED radiation curable protective varnish are dispersed in a mixture of the liquid ingredients comprised by the protective varnish. The non-ionic surfactant, the photoinitiator of general formula (I), the diaryliodonium salt, and the radical photoinitiator can be added to the mixture simultaneously or sequentially during the dispersion or mixing step of all other ingredients, or at a later stage, i.e. just before the hybrid UV-LED radiation curable protective varnish is applied onto the surface of the substrate of the security document and / or the surface of one or more security features of the security document.

[0504] Preferably, the hybrid 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.

[0505] In a preferred embodiment, the hybrid UV-LED radiation curable protective varnish is a flexographic printing varnish. Flexographic printing preferably uses a unit with a doctor blade, preferably a chambered doctor blade, anilox roll and a printing plate cylinder. The anilox roll advantageously has small cells that determine the volume and / or density of the curable varnish application speed. The doctor blade is pressed against the anilox roll and at the same time scrapes off the remaining varnish. The anilox roll transfers the varnish to the printing plate cylinder, which finally transfers the varnish to the substrate. The specific design can be achieved using a designed photopolymer plate. The printing plate cylinder can be made of a polymeric or elastomeric material. Polymers are mainly used as photopolymer in the plate and sometimes as a seamless coating on the sleeve. The photopolymer plate is made of a photosensitive polymer that is hardened 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 areas. The plate is then processed to remove the unhardened photopolymer from the non-image areas, which reduces the plate surface in these non-image areas. After processing, the plate is dried and given a post-exposure dose of UV light to cure the entire plate. The preparation of printing plate cylinders for flexographic printing is described in Printing Technology by J. M. Adams and P. A. Dolin (Delmar Thomson Learning, 5th edition, pages 359-360). In order to be suitable for printing by flexographic printing, the hybrid UV-LED radiation curable protective varnish must have a viscosity in the range from about 50 to about 500 mPas at 25 °C, which is measured using a Brookfield viscometer (model "DV-I Prime") equipped with spindle S21 for measuring viscosities comprised between 100 mPa-s ~ 500 mPa-s at 100 rpm at 25 °C, or is measured using a rotational viscometer DHR-2 of TA Instruments (cone-plate geometry, diameter 40 mm) for measuring viscosities below 100 mPa-s at 25 °C and 1000 s"1. -1

[0506] ​In a further preferred embodiment according to the application, the hybrid UV-LED radiation curable protective varnish is an inkjet printing varnish, preferably a drop-on-demand (DOD) inkjet printing varnish. Drop-on-demand (DOD) printing is a non-contact printing process in which droplets are generated only when printing is required and are usually generated by a jetting mechanism rather than by making a jet unstable. Depending on the mechanism used in the print head to generate the droplets, DOD printing is divided into piezoelectric impulse, thermal jet and valve jet. In order to be suitable for DOD inkjet printing, the hybrid UV-LED radiation curable protective varnish must have a low viscosity of less than about 20 mPa-s and a surface tension of less than about 45 N / m at the jetting temperature.

[0507] In still a preferred embodiment according to the application, the hybrid UV-LED radiation curable protective varnish is a screen printing varnish. As is well known to the person skilled in the art, screen printing (also referred to in the art as silkscreen printing) is a printing technique that usually uses a screen made of woven mesh to support an ink-blocking stencil. The attached stencil forms a web-like open area that transfers the varnish as a sharply defined image onto a substrate. A squeegee moves across 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 thicker varnish deposits can be applied on the substrate compared to other printing techniques. Thus, screen printing is also preferred when varnish deposits of a thickness of values between about 10 to 50 pm or more are required, which cannot (easily) be achieved with other printing techniques. Typically, the screen is made of a piece of porous, finely woven fabric called a mesh stretched over a frame of e.g. aluminum or wood. Currently, most meshes are made of artificial materials such as synthetic threads or steel threads. Preferred synthetic materials are nylon or polyester threads.

[0508] In addition to screens made on the basis of woven meshes based on synthetic threads or metal threads, screens have also been developed from solid metal sheets with a grid of holes. Such screens are prepared by a process comprising the steps of forming a screen skeleton by means of an electrolytic cell in which a screen skeleton is formed on a substrate provided with a separating agent, peeling the formed screen skeleton from the substrate and electrolyzing the screen skeleton in a second electrolytic cell in order to deposit metal onto the skeleton, thereby electrolytically forming a metal screen.

[0509] There are three types of screen printing machines, namely flat bed, rotary and rotary screen printing machines. Flat bed and rotary screen printing machines are similar in that both use a flat screen and a three-step reciprocating process to perform the printing operation. First the screen is moved into position over the substrate, then a squeegee is pressed against the screen and drawn across the image area, and then the screen is lifted off the substrate to complete the process. With flat bed machines the substrate to be printed is usually placed on a horizontal printing platform parallel to the screen. With rotary machines the substrate is mounted on a cylinder. Flat bed and rotary screen printing processes are discontinuous processes and therefore speed is limited, typically a maximum of 45 m / min in web or 3,000 sheets / hour in a sheet-fed process.

[0510] In contrast, rotary screen printing machines are designed for continuous, high speed printing. The screens used on rotary screen printing machines are for example thin metal cylinders usually obtained using the electroforming method described above or thin metal cylinders made of woven steel wire. The open ended cylinder is capped at both ends and mounted in blocks on the sides of the printing machine. During printing varnish is pumped into one end of the cylinder so that a fresh supply is constantly maintained. The squeegee is fixed inside the rotating screen, maintaining and adjusting the squeegee pressure to obtain good and constant print quality. The advantage of rotary screen printing machines is that the speed in web can easily reach 150 m / min or the speed in a sheet-fed process can easily reach 10,000 sheets / hour.

[0511] Screen printing is further described in for example R.H. Leach and R.J. Pierce, The Printing Ink Manual (Springer Edition, 5thedition, pages 58-62), J.M. Adams and P.A. Dolin, Printing Technology (Delmar Thomson Learning, 5thedition, pages 293-328), and H. Kipphan, Handbook of Print Media (Springer, pages 409-422 and 498-499).

[0512] The hybrid 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. The hybrid UV-LED radiation curable protective varnish claimed and described herein is also suitable for curing using medium pressure mercury lamps, as is well known to the person skilled in the art.

[0513] Another aspect according to the present application relates to a method of coating a security document comprising a substrate and one or more security features applied on or inserted into a portion of the substrate, wherein said method comprises the following steps:

[0514] i) applying the hybrid UV-LED radiation curable protective varnish claimed and described herein on the surface of the substrate of the security document and / or on the surface of the one or more security features, preferably by a printing method selected from flexographic printing, inkjet printing and screen printing, so as to form a varnish layer; and;

[0515] ii) curing the varnish layer by exposure to UV light emitted by a UV-LED source, so as to form a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features.

[0516] Preferably, at least one of the one or more security features applied on or inserted into a portion of the substrate of the security document to be coated is a UV light excitable luminescent security feature, i.e. a security feature that luminesces in response to excitation by UV light, in particular UV light having a wavelength of 254 nm or 366 nm.

[0517] Preferably, step ii) described herein consists in exposing the varnish layer to one or more wavelengths between about 365 nm and about 405 nm emitted by one or more UV-LED sources, so as to form a protective coating covering the surface of the substrate of the security document and / or the surface of the 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 consists in exposing the varnish layer to a single wavelength between 365 nm and 405 nm, such as 365 nm, 385 nm, 395 nm or 405 nm, emitted by a UV-LED source, so as to form a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features. The varnish layer is preferably exposed at a dose of at least 150 mJ / cm 2 , more preferably at a dose of at least 200 mJ / cm 2 , and particularly preferably at a dose of at least 220 mJ / cm2 to UV light in order to cure the varnish layer and form a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features. As described below, the UVPower II radiometer to measure the dose.

[0518] As used herein, the term "substrate" includes any security document substrate in a portion of which a security feature can be inserted and / or to which a security feature can be applied. Security 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 abaca, 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 paper currency, while wood pulp is typically used for non-currency security documents. Typical examples of plastics and polymers include polyolefins such as polyethylene (PE) and polypropylene (PP), polyamides such as poly(ethylene terephthalate) (PET), poly(l,4-butylene terephthalate) (PBT), poly(ethylene 2,6-naphthalate) (PEN), and polyvinyl chloride (PVC). Typical examples of composite materials include, without limitation, multilayer structures or laminates of paper and at least one plastic or polymeric material, such as those described above. The substrate of a security document can be printed with any desired indicia, including any symbols, images, and patterns, and / or can include one or more security features, including luminescent security features.

[0519] Another aspect according to the present application relates to a security document comprising a substrate, one or more security features applied on or inserted into a portion of the substrate, and a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features, wherein the protective coating is obtained by the coating process claimed and described herein, which comprises the following steps:

[0520] i) applying a mixed UV-LED radiation curable protective varnish as claimed and described herein on the surface of the substrate of the security document and / or the surface of the one or more security features, preferably by a printing method selected from flexographic printing, inkjet printing, and screen printing, more preferably by flexographic printing, in order to form a varnish layer; and

[0521] ii) curing the varnish layer by exposure to UV light emitted by a UV-LED source in order to form a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features.

[0522] The security document according to the present application can comprise on one side thereof between about 5% and about 15% of the substrate surface of an unprotected coating area, wherein the percentage is based on the total surface of the security document. Preferably, the unprotected coating area is present on at least one edge or corner of the substrate. The unprotected coating area can be used for example for numbering the security document. If the security document is a banknote, the uncoated area can additionally be used for absorbing a colored (non-erasable) ink for protecting the banknote against theft and robbery as described in International Patent Application Publication No. WO2013127715A2.

[0523] Another aspect according to the present application relates to a protective coating for a security document comprising a substrate, and one or more security features applied on or inserted into a portion of the substrate, wherein the protective coating is obtained from the hybrid UV-LED radiation curable protective varnish as claimed and described herein. In particular, the above protective coating is obtained by:

[0524] i) applying the hybrid UV-LED radiation curable protective varnish as claimed and described herein on the surface of the substrate of the security document and / or on the surface of the one or more security features, preferably by a printing method selected from flexographic printing, inkjet printing and screen printing, more preferably by flexographic printing, to form a varnish layer; and

[0525] ii) curing the varnish layer by exposure to UV light emitted by a UV-LED source, so as to form a protective coating covering the surface of the substrate of the security document and / or the surface of the one or more security features.

[0526] Preferably, at least one of the one or more security features applied on or inserted into a portion of the substrate of the security document to be coated is a UV light excitable luminescent security feature, i.e. a security feature that luminesces in response to excitation by UV light, in particular UV light having a wavelength of 254 nm or 366 nm.

[0527] As used herein, the term "security document" means a document having for example a value that makes it susceptible to being easily counterfeited or illegally reproduced, and is generally protected against counterfeiting or fraud by at least one security feature. Typical examples of security documents include, without limitation, banknotes, deeds, tickets, checks, vouchers, tax stamps and tax labels, agreements, etc., identity documents such as passports, identity cards, visas, bank cards, credit cards, transaction cards, access documents, entrance tickets, etc.

[0528] EMBODIMENTS

[0529] 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 hybrid UV-LED radiation-curable protective varnish according to the invention.

[0530] Photosensitizer

[0531] Table 1A

[0532]

[0533]

[0534]

[0535]

[0536] a) Molecular weight was calculated using ChemDraw Professional (version 20.0.0.41).

[0537] Measurement of the weight average molecular weight

[0538] The weight-average molecular weights of the oligomeric photosensitizers S1-S3 were independently determined by GPC (gel permeation chromatography) according to the following method (based on OECD test method 118):

[0539] 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 were established using six polystyrene standards (molecular weight range 472 to 512000 g / mol) (log(molecular weight) = f(retention volume)). Two Viskotek™ 4008L 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. 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 using the following formula: polystyrene equivalent weight-average molecular weight (PS eq M). W The average of three measurements at a 95% confidence level and with the same solution:

[0540]

[0541] where H i is the level of the detector signal from the baseline of the retention volume V i , M i is the molecular weight of the compound fraction at the retention volume V i , and n is the number of data points. The Omnisec 5.12 supplied with the equipment was used as software. The PS eq M w measured for S1, S2 and S3 are shown in Table 1A above.

[0542] Sulfur molar concentration in thioxanthone-based photosensitizers S1-S8

[0543] The sulfur molarity (sulfur (mmol) / photosensitizer (g)) corresponds to the molarity of the reactive thioxanthone moiety (reactive thioxanthone moiety (mmol) / photosensitizer (g)) and is used to ensure that all thioxanthone photosensitizers are used at the equivalent molarity of the reactive thioxanthone moiety. The sulfur molarity is obtained by ED-XRF measurement of the sulfur atoms (photosensitizers S1-S3) or by direct determination using the molecular weight as calculated with ChemDraw Professional (version 20.0.0.41) of the known structure (photosensitizers S4-S8).

[0544] Determination of the sulfur molar concentration in oligomeric photosensitizers S1-S3 by ED-XRF

[0545] The sulfur molarity in the oligomeric photosensitizers S1-S3 was determined by ED-XRF (Spectro XEPOS) using an internal standard addition technique and the sulfur atom signal. For each of the oligomeric photosensitizers S1-S3 of Table 1A, three 50 mL solutions of the respective photosensitizer at 2 mg / mL in acetonitrile (Sigma-Aldrich, 99.9%) were prepared. From each solution, a 5 mL sample was collected and increasing amounts of a 5 mg / mL solution of Genocure ITX (Rahn, 99.3% according to analysis certificate) in acetonitrile were added. Each sample was completed to 10 mL with acetonitrile. The following solutions have been obtained and are provided in Table 1B.

[0546] Table 1B

[0547] Grade 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

[0548] Each sample was independently subjected to ED-XRF measurement (Spectro XEPOS) and the spectrum was recorded. From all spectra the blank measurement (pure acetonitrile) was derived. For each series of samples (triplicate measurements) the measured fluorescence intensity at 2.31 keV (S Kα1 peak) was shown as a function of the molar concentration of sulfur (mmol / ml) contained in the added Genocure ITX and a linear regression was performed. The absolute value of the x-axis intercept of the regression line indicated the molar concentration of sulfur in the 0th order in each sample. The average values (average of the triplicate measurements) are provided in Table 1C. The respective average values were used to determine the molar concentration of sulfur (sulfur (mmol) / photosensitizer (g)) in each oligomeric photosensitizer S1-S3 and to calculate the amount (wt-%) of oligomeric photosensitizer S1-S3 added for the preparation of the examples and comparative examples.

[0549] Table 1C summarizes the determined (photosensitizers S1-S3) and calculated (photosensitizers S4-S8) molar concentrations of sulfur (sulfur (mmol) / photosensitizer (g)) corresponding to the molar concentration of the reactive thioxanthone-based moiety (reactive thioxanthone-based moiety (mmol) / photosensitizer (g)).

[0550] Table 1C

[0551]

[0552]

[0553] Cationic photoinitiator

[0554] Table 1D

[0555]

[0556] Radical photoinitiator

[0557] Table 1E

[0558]

[0559] a) The molecular weights of the radical photoinitiators RP1-RP4 were obtained from SciFinder.

[0560] Other ingredients

[0561] Table 1F

[0562]

[0563] Preparation of mixed UV-LED radiation curable protective varnishes E1-E10, comparative mixed varnishes C1-C5, C6a-C11a, C6b-C11b and C12 and protective coatings obtained therefrom according to the present application A1. Preparation of mixed UV-LED radiation curable protective varnishes (E1-E3) and comparative varnishes (C1-C2) according to the present application

[0564] A2. Preparation of protective coatingsA3. Evaluation of the curing performance of mixed UV-LED radiation curable varnishes E1-E3 and comparative varnishes C1-C2 using the MEK rub test

[0565] 100 g of each of the hybrid UV-LED radiation curable protective varnishes (E1-E3) according to the application and comparative varnishes C1-C2 were prepared by first premixing the first three ingredients of Table 2A (cycloaliphatic epoxide, oxetane and radical oligomer) using a Dispermat (model CV-3) at 1500 rpm for 5 minutes, then adding and dispersing the matting agent at 1500 rpm over about 25 minutes, and finally adding the other ingredients at 1500 rpm over about 15 minutes and further mixing the mixture thus obtained. The hybrid UV-LED radiation curable protective varnishes E1-E3 and comparative varnishes C1-C2 had viscosity properties making them suitable for flexographic and screen printing.

[0566] Table 2A. Composition of the hybrid UV-LED radiation curable protective varnishes E1-E3 and comparative varnishes C1-C2

[0567]

[0568] a) Concentration in the reactive thioxanthone-based moiety (1-chloro-4- carboxymethoxy-thioxanthone moiety) (reactive thioxanthone-based moiety (mmol) (1-chloro-4-carboxymethoxy-thioxanthone moiety) / 100 g of varnish.

[0569] Varnish

[0570] The protective varnishes E1-E3 and comparative varnishes C1-C2 according to the application were independently applied by hand using a manual coating machine unit (RK-print) with n° 0 bar, on a piece of fiduciary polymeric substrate (Guardian TM ) from CCL Secure, to provide a varnish layer of dimensions about 5 cm x 10 cm, thickness about 4 pm. Subsequently, the varnish layer was exposed to UV-A radiation by means of a UV-A lamp from IST Metz GmbH (100% lamp power, 70% duty cycle, nominal lamp to sample distance of 20 mm, resulting in about 220 mJ / cm 2The varnish layer was exposed to UV light twice at a speed of 150 m / min under a UV-LED curing unit LUV20 emitting at 385 nm under UV-LED at a controlled relative humidity to cure each of the varnish layers. The dose was measured by the Powerpuck II device under UV-LED in similar conditions as the cured samples (same speed and same distance between the lamp and the sample / detector). The dose is given for the UV-A2 range, selected by a specific filter in the device (370-415 nm). The conditions used to cure the coated substrates are similar to the curing conditions expected in an industrial environment.

[0571] Relative humidity [% rH] Poor

[0572] The protective coating obtained as described in item A2 above was stored in the dark for 24 hours. After this period, the deep cure performance of each protective coating was evaluated by the following procedure, which is an indication of the cure performance of the varnish used to obtain the protective varnish:

[0573] - a cotton swab was immersed in 99.5% methyl ethyl ketone (MEK) (Brenntag);

[0574] - each protective coating was rubbed with the cotton swab for 50 times with a light hand pressure on an area of about 0.5 cm x 5 cm, after 30 seconds the rubbed area was visually evaluated. The results of the visual evaluation summarized in Table 2B are classified as follows:

[0575] “Poor”: the MEK rub test resulted in partial or total removal of the protective varnish, which indicates that the cure of the protective coating was insufficient, the varnish presents a poor cure performance,

[0576] “Acceptable”: the MEK rub test was visually detectable, the protective coating was not removed, which indicates that the cure of the protective coating was acceptable and the varnish presents an acceptable cure performance,

[0577] “Best”: the MEK rub test was not visually detectable, which indicates that the cure of the protective coating was the best, the varnish presents a best cure performance.

[0578] The varnishes with acceptable and best cure performance under the curing conditions described herein are suitable for the industrial production of security document protective coatings.

[0579] Table 2B. MEK rub test results

[0580] Best C1 E1 E2 E3 C2 Best 45 45 47 45 45 curing a) ]]> Best Best A4. Evaluation of the fluorescence exhibited by protective coatings (varnishes E1-E3 and comparative varnish C2) having the best curing performance determined by the MEK rub test Relative fluorescence values at 254 / 366 nm Visual perception

[0581] a) Cure determined by MEK rub test after 24 hours.

[0582] Low fluorescence, close to the comparative standard Acceptable fluorescence

[0583] The protective coatings obtained with the varnishes having the best curing properties determined by the MEK rub test, i.e. the residual fluorescence exhibited by the protective coatings obtained from the varnishes E1-E3 according to the application and the comparative varnish C2, were evaluated using the method described below. Table 2D gives the fluorescence results.

[0584] The residual fluorescence of the protective coatings was evaluated using a Fluorolog II (Spex) apparatus at 254 nm and 366 nm using the following parameters:

[0585] Detector: R928 / 0115 / 0381

[0586] Angle: 30°

[0587] Position: face-on

[0588] Excitation slit: 2 nm (254 nm) and 2 nm (366 nm)

[0589] Integration time: 0.1 s

[0590] Coverage wavelength: 400-700 nm (increment 1 nm)

[0591] Detection slit: 1 nm (254 nm) and 1 nm (366 nm), UV filter (400 nm and below) to avoid detection of the excitation light

[0592] From the spectra obtained, the maximum fluorescence intensity was determined and the values obtained were reported as absolute values in photons / s, as shown in Table 2D.

[0593] The absolute intensity at maximum fluorescence (in photons / s) measured for each protective coating obtained from the mixed UV-LED radiation curable protective varnishes E1-E3 according to the application and the comparative varnish C2 was compared with the absolute intensity at maximum fluorescence of the comparative standards (ST1-ST2). Said comparative standards were prepared with mixed varnishes having compounds considered by the skilled person to exhibit low intrinsic fluorescence and / or to be able to generate only minimal amounts of fluorescent degradation products upon curing under standard mercury lamps. The comparative standards ST1 and ST2 were prepared simultaneously with the protective coatings that they served as comparative standards. The residual fluorescence of the comparative standards (ST1-ST2) was measured simultaneously with the residual fluorescence of the protective coatings that they served as comparative standards.

[0594] Table 2C. Composition of the standard mixed protective varnishes curable with mercury lamps (for the production of the comparative standards ST1, ST2 and ST3)

[0595]

[0596] The standard hybrid protective varnish described in Table 2C was applied using a manual coating machine unit (RK-print) with n° 0 bar onto a piece of fiducial polymer substrate (Guardian TM ) to form a varnish layer having dimensions of about 5 cm x 10 cm and a thickness of about 4 pm. The varnish layer was cured under controlled relative humidity by exposing it twice to UV-Vis light at a speed of 100 m / min under a mercury lamp unit (IST Metz GmbH; two lamps: iron-doped mercury lamp + mercury lamp), generating comparative standards ST1 -ST2.

[0597] The curing of each individual comparative standard ST1 -ST2 was evaluated after 24 h of storage in the dark using the MEK rub test described in item A3 above. Comparative standards ST1 -ST2 showed the best curing.

[0598] Table 2D shows the absolute intensity at maximum fluorescence of the protective coatings obtained from varnishes E1 -E3 and comparative varnish C2 and the corresponding comparative standards (ST1 -ST2) at maximum fluorescence (in photons / sec), as well as the ratio between the absolute intensity at maximum fluorescence of each protective coating and the absolute intensity at maximum fluorescence of the corresponding comparative standard ST1 -ST2 (relative fluorescence value).

[0599] Table 2D. Results of the fluorescence measurements

[0600]

[0601] The fluorescence of the protective coatings obtained from hybrid UV-LED radiation curable protective varnishes E1 -E3 and comparative varnish C2 according to the present application was also visually assessed using a CAMAG UV Cabinet 4 (equipped with two UV tubes at 254 nm and 366 nm, each 8 W). The visual perception was correlated with the measured relative fluorescence values determined as described above. Table 2E summarizes the correlation between the visual perception and the measured relative fluorescence values.

[0602] Table 2E

[0603] Excessive fluorescence B1. Preparation of mixed UV-LED radiation curable protective varnishes E4-E7 and comparative varnishes C3-C5 according to the present application <1.3 B2. Preparation of protective coatings 1.3-1.6 B3. Evaluation of the curing performance of mixed UV-LED radiation curable varnishes E4-E7 and comparative varnishes C3-C5 using the MEK rub test >1.6 B4. Evaluation of the fluorescence exhibited by protective coatings (varnishes E4-E7 according to the present application and comparative varnishes C4-C5) having acceptable / best curing performance determined by the MEK rub test

[0604] Protective varnishes are usually applied on the entire surface and on both sides of a security document. Therefore, protective coatings exhibiting a relative fluorescence higher than 1.6 (compared to comparative standards ST1 -ST2) tend to make the visual observation and / or the machine readability of luminescent security features present in said security document difficult or even impossible.

[0605] As shown by the experiments performed with the protective varnishes E1-E3 according to the application, the mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) and a concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moiety of about 1.3 mmol to about 2.6 mmol per 100 g of protective varnish exhibit the best curing performance and an acceptable fluorescence at 254 nm and 366 nm. Mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) but a concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moiety lower than about 1.3 mmol per 100 g of protective varnish, such as comparative varnish C1, show poor curing performance. Mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) but a concentration of the 1-chloro-4-carboxymethoxy-thioxanthone moiety higher than 2.6 mmol per 100 g of protective varnish, such as comparative varnish C2, have good curing performance but produce protective coatings showing an excessive fluorescence, which is not acceptable for protective varnishes used in security documents.

[0606] C1. Preparation of mixed UV-LED radiation curable protective varnishes E8-E10 according to the present application

[0607] 100 g of each of the mixed UV-LED radiation curable protective varnishes (E4-E7) and comparative varnishes C3-C5 according to the application were prepared using the ingredients shown in Table 3A, in the same way as described under item A1 for varnishes E1-E3 and comparative varnishes C1-C2. The mixed UV-LED radiation curable protective varnishes E4-E7 and comparative varnishes C3-C5 have viscosity properties that make them suitable for flexographic and screen printing.

[0608] Table 3A. Composition of the mixed UV-LED radiation curable protective varnishes E4-E7 and comparative varnishes C3-C5

[0609]

[0610] a) concentration of the reactive thioxanthone-based moiety (2-keto-thioxanthone moiety) in the varnish (reactive thioxanthone-based (2-keto-thioxanthone) moiety (mmol) per 100 g of varnish)

[0611] C2. Preparation of protective coatings

[0612] Protective coatings were prepared from the mixed LED-UV curable protective varnishes E4-E7 and comparative varnishes C3-C5 according to the application in the same way as described under item A2.

[0613] C3. Evaluation of the curing performance of mixed UV-LED radiation curable varnishes E8-E10 using the MEK rub test Varnish

[0614] The protective coatings obtained as described under item B2 above were stored in the dark for 24 hours. After this period, the deep curing performance of each protective coating was evaluated after this period as described under item A3 above, which is an indication of the curing performance of the varnish used to obtain said protective varnish. The test results are shown in Table 3B.

[0615] Table 3B. Results of the MEK rub test

[0616]

[0617] a) Curing determined by the MEK rub test after 24 hours.

[0618] Relative humidity [% rH] Best

[0619] The protective coatings obtained with acceptable to optimal curing performance by the MEK rub test, i.e. the fluorescence exhibited by the protective coatings obtained from varnishes E4-E7 and comparative varnishes C4-C5 according to the application, were evaluated using the method described under item A4 above. Table 3C gives the fluorescence results.

[0620] Using the compositions described in Table 2C, comparative standards ST1 and ST2 were prepared simultaneously with their protective coatings as comparative standards, as described under item A4. The residual fluorescence of the comparative standards (ST1-ST2) was measured simultaneously with the residual fluorescence of their protective coatings as comparative standards.

[0621] Table 3C. Results of the fluorescence measurement

[0622]

[0623] The fluorescence of the protective coatings obtained from comparative mixed UV-LED radiation curable protective varnishes E4-E7 and comparative varnishes C4-C5 was also visually evaluated using a CAMAG UV Cabinet 4 (equipped with two UV tubes at 254 nm and 366 nm, each 8 W). The visual perception was correlated with the measured relative fluorescence values as determined under item A4, Table 2E above.

[0624] Protective varnishes are typically applied on the entire surface and on both sides of a security document. Therefore, protective coatings exhibiting a relative fluorescence higher than 1.6 (compared to comparative standards ST1-ST2) tend to make the visual observation and / or the machine readability of luminescent security features present in said security document difficult or even impossible.

[0625] As shown by the experiments performed with the protective varnishes E4-E7 according to the application, the mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) and having a concentration of the 2-keto-thioxanthone moiety of about 1.3 mmol to about 3.2 mmol per 100 g of protective varnish exhibit acceptable to optimal curing performance and low to acceptable fluorescence at both 254 nm and 366 nm. Mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) but having a concentration of the 2-keto-thioxanthone moiety lower than about 1.3 mmol per 100 g of protective varnish, such as the comparative varnishes C3, show poor curing performance. Mixed UV-LED radiation curable protective varnishes comprising the photosensitizer of general formula (I) but having a concentration of the 2-keto-thioxanthone moiety higher than 3.2 mmol per 100 g of protective varnish, such as the comparative varnishes C4 and C5, have good curing performance but produce protective coatings showing excessive fluorescence.

[0626] Acceptable

[0627] 100 g of each of the mixed UV-LED radiation curable protective varnishes according to the application (E8-E10) were prepared using the ingredients shown in Table 4A in the same manner as described under item A1 for varnishes E1-E3 and comparative varnishes C1-C2. The mixed UV-LED radiation curable protective varnishes E8-E10 comprise the same molar concentration of radical photoinitiator (radical photoinitiator (mmol) per 10 g of varnish) as the mixed UV-LED radiation curable protective varnishes E4 and E5. The mixed UV-LED radiation curable protective varnishes E8-E10 have viscosity properties that make them suitable for use in flexographic and screen printing.

[0628] Table 4A. Composition of the mixed UV-LED radiation curable protective varnishes E8-E10

[0629]

[0630] a) Concentration of the reactive thioxanthone-based moiety (2-keto-thioxanthone) in the varnish (reactive thioxanthone-based (2-keto-thioxanthone) moiety (mmol) per 100 g of varnish)

[0631] Acceptable

[0632] Protective coatings were prepared from the mixed LED-UV curable protective varnishes E8-E10 according to the application in the same manner as described under item A2.

[0633] C4. Evaluation of the fluorescence exhibited by protective coatings (varnishes E8-E10) having acceptable / best curing performance determined by the MEK rub test

[0634] The protective coatings obtained as described under item C2 above were stored in the dark for 24 hours. After this period, the deep curing performance of each protective coating was evaluated after this period as described under item A3 above, which is an indication of the curing performance of the varnish used to obtain said protective varnish. The test results are shown in Table 4B.

[0635] Table 4B. Results of the MEK rub test

[0636] D1. Preparation of comparative varnishes C6a-C11a, C6b-C11b and C12 E8 E9 E10 D2. Preparation of protective coatings 45 45 45 curing a) ]] D3. Evaluation of the curing performance of comparative mixed varnishes C6a-C11a, 6b-C11b and C12 using the MEK rub test D4. Evaluation of the fluorescence exhibited by protective coatings having acceptable / best curing performance determined by the MEK rub test ​

[0637] a) Curing determined by the MEK rub test after 24 hours.

[0638] ​ ​

[0639] The protective coatings obtained with varnishes having an acceptable / optimal curing performance determined by the MEK rub test, i.e. the protective coatings obtained from varnishes E8-E10, were evaluated for the fluorescence they exhibited using the method described under item A4 above. The fluorescence results are given in Table 4C.

[0640] The comparative standard ST1 was compared with its protective coating as comparative standard, both prepared as described under item A4, using the compositions described in Table 2C.

[0641] The residual fluorescence of the comparative standard ST1 was compared with the residual fluorescence of its protective coating as comparative standard, both measured simultaneously.

[0642] Table 4C. Results of the fluorescence measurements

[0643]

[0644] The fluorescence of the protective coatings obtained from the mixed UV-LED radiation curable protective varnishes E8-E10 was also visually evaluated using a CAMAG UV Cabinet 4 (equipped with two UV tubes at 254 nm and 366 nm, each 8 W). The visual perception was correlated with the measured relative fluorescence values determined as described above under item A4, Table 2E. The protective varnishes are typically applied on the entire surface and on both sides of the security document. Therefore, protective coatings exhibiting a relative fluorescence higher than 1.6 (compared to the comparative standard ST1) tend to make the visual observation and / or the machine readability of the luminescent security features present in said security document difficult or even impossible.

[0645] The curing and fluorescence properties of the coatings obtained with the protective varnishes E8-E10, E4 and E5 according to the application are comparable, the curing and fluorescence properties of the coatings being different by the structure of the free radical photoinitiator (Omnirad 2959 for E4 and E5; Omnirad 184 for E8; Genocure MBF for E9; Genocure BDK for E10) and / or the structure of the diaryliodonium photoinitiator (Omnicat 440 for E4, E8, E9 and E10; Speedcure 938 for E5).

[0646] ​

[0647] 100 g of each of the comparative hybrid UV-LED radiation curable protective varnishes C6a-C11a, 6b-C11b and C12 were prepared using the ingredients shown in Table 5A in the same manner as described under item A1 for varnishes E1-E3 and comparative varnishes C1-C2.

[0648]

[0649] ​

[0650] The protective coatings were prepared from the comparative hybrid varnishes C6a-C11a, 6b-C11b and C12 according to the application in the same manner as described under item A2.

[0651] ​

[0652] The protective coatings obtained as described under item D2 above were stored in the dark for 24 hours. After this period, the deep curing properties of each protective coating were evaluated after this period as described under item A3 above, which are indicative of the curing properties of the varnish used to obtain the protective varnish. The test results are shown in Table 5B.

[0653] Table 5B. MEK rub test results

[0654]

[0655] a) Curing determined by the MEK rub test after 24 hours.

[0656] ​ ​

[0657] The protective coatings obtained with varnishes having acceptable or optimal curing properties determined by the MEK rub test, i.e. the fluorescence exhibited by the protective coatings obtained from the comparative hybrid UV-LED radiation curable protective varnishes C6b, C7b, C8b, C9b, C10b, C11b and C12 were evaluated using the following method.

[0658] Table 5C gives the fluorescence results.

[0659] The comparative standards ST1 and ST3 were compared with their protective coatings as comparative standards, both prepared as described under item A4, using the compositions described in Table 2C.

[0660] The residual fluorescence of the comparative standards ST1 and ST3 was compared with the residual fluorescence of their protective coatings as comparative standards, both measured simultaneously.

[0661] Table 5C. Results of the fluorescence measurements

[0662]

[0663] The fluorescence of the protective coatings obtained from the comparative mixed UV-LED radiation curable protective varnishes C6b, C7b, C8b, C9b, C10b, C11 b and C12 was also visually assessed using a CAMAG UV Cabinet 4 (equipped with two UV tubes at 254 nm and 366 nm, each 8 W). The visual perception was correlated with the measured relative fluorescence values as determined in item A4, Table 2E, above. The protective varnishes were typically applied on the entire surface and on both sides of a security document. Therefore, protective coatings exhibiting a relative fluorescence higher than 1.6 (compared to the comparative standards ST1 and ST3) tend to make the visual observation and / or the machine readability of luminescent security features present in said security document difficult or even impossible.

[0664] As shown by the experiments performed with the comparative varnishes C6a, C7a, C8a, C9a, C10a and C11 a, the mixed varnishes containing a small amount of thioxanthone comprising a photosensitizer other than the photosensitizer of general formula (I) described herein have poor curing performance and result in a coating that is not adequately cured using curing conditions suitable for industrial coating methods.

[0665] As shown by the experiments performed with the comparative varnishes C6b, C7b, C8b, C9b, C10b and C11 b, the mixed varnishes having a good curing performance, but generating protective coatings exhibiting an excessive fluorescence (in particular at 254 nm), comprise a reactive thioxanthone-based moiety containing a photosensitizer other than the photosensitizer of general formula (I), wherein the concentration of the reactive thioxanthone-based moiety is within the claimed range.

[0666] As shown by the experiments performed with the comparative varnish C12, the mixed UV-LED radiation curable protective varnish comprising a thioxanthone photoinitiator instead of a diaryliodonium photoinitiator and 9,10-dibutoxyanthracene as photosensitizer has a good curing performance, but generates a protective coating showing an extremely high fluorescence.

Claims

1. A hybrid UV-LED radiation-curable protective varnish, comprising: a) 60 wt% to 85 wt% of an alicyclic epoxide or a mixture of an alicyclic epoxide with one or more cationic curable monomers other than the alicyclic epoxide; b) 3 wt% to 15 wt% of one or more free radical-curable monomers and / or oligomers; c) 1 wt% to 6 wt% of diaryliodomonium salts; d) 0.5 wt% to 3 wt% of a free radical photoinitiator, wherein the free radical photoinitiator is selected from the group consisting of α-hydroxy ketones, α-alkoxy ketones, benzyl diketals, benzoin ethers, phosphine oxides, phenyl glyoxylates, and mixtures thereof; e) 0.01 wt% to 5 wt% of nonionic surfactants; and f) Photosensitizers of general formula (I) In general formula (I) i)A 1 and A 2 Selected independently from hydrogen and the following structural components -L 1 -Selected from -L 2 -Selected from n1 and n2 are integers greater than or equal to 0; m represents 0; B represents hydrogen; C is selected from hydrogen, A 3 and A 4 Each is independently selected from hydrogen and the following structural components: -L 3 -and-L 4 - Selected independently from each other And n3 and n4 are integers greater than or equal to 0, where The sum of n1 + n2 is included in the range of 2 to 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 to 16; or ii) A 1 and A 2 Selected independently from hydrogen and the following structural components -L 1 -Selected from -L 2 -Selected from n1 and n2 are integers greater than or equal to 0; m represents 1; B is selected from ethyl, and C is selected from 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 each other 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 to 12; The sum of n1+n2+n3+n4 is included in the range of 4 to 16; The sum of n1+n2+n3+n4+n6 is included in the range of 5 to 15; The sum of n1+n2+n3+n5 is included in the range of 4 to 16; The sum of n1+n2+n3+n4+n5 is included in the range of 5 to 15; The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6 to 18; The UV-LED radiation-curable protective varnish includes a portion of the photosensitizer of general formula (I). A concentration of 1.3 mmol to 3.2 mmol per 100 g of mixed UV-LED radiation can cure the portion of the protective varnish. or iii)A 1 and A 2 Selected independently from hydrogen and the following structural components -L 1 -Selected from -L 2 -Selected from n1 and n2 are integers greater than or equal to 0; m represents 0; B represents hydrogen; C is selected from hydrogen, A 3 and A 4 Each is independently selected from hydrogen and the following structural components: -L 3 -and-L 4 - Selected independently from each other And n3 and n4 are integers greater than or equal to 0, where The sum of n1 + n2 is included in the range of 2 to 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 to 16; or iv) A 1 and A 2 Selected independently from hydrogen and the following structural components -L 1 -Selected from -L 2 -Selected from n1 and n2 are integers greater than or equal to 0; m represents 1; B is selected from ethyl, and C is selected from 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 each other 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 to 12; The sum of n1+n2+n3+n4 is included in the range of 4 to 16; The sum of n1+n2+n3+n4+n6 is included in the range of 5 to 15; The sum of n1+n2+n3+n5 is included in the range of 4 to 16; The sum of n1+n2+n3+n4+n5 is included in the range of 5 to 15; The sum of n1+n2+n3+n4+n5+n6 is included in the range of 6 to 18; The UV-LED radiation-curable protective varnish includes a portion of the photosensitizer of general formula (I). The concentration of the mixed UV-LED radiation per 100g can cure the protective varnish at a concentration of 1.3mmol to 2.6mmol. The weight percentage is based on the total weight of the hybrid UV-LED radiation-curable protective varnish.

2. The hybrid 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 hybrid 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 hybrid UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has general formula (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 hybrid UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has the general formula (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 hybrid UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the photosensitizer has the general formula (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 hybrid 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 by any one of claims 1-3.

8. The mixed UV-LED radiation-curable protective varnish according to any one of claims 1-3, wherein the diaryliodonium salt has the general formula (II). in R 1 -R 10 They are independently selected from hydrogen, C1-C 18 -alkyl and C1-C 12 -alkoxy group; and An - 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.

9. The mixed 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 epoxide are selected from the group consisting of: vinyl ethers, allyl ethers, cyclic ethers other than alicyclic epoxides, lactones, cyclic sulfides, vinyl sulfides, allyl sulfides, hydroxyl-containing compounds, and mixtures thereof.

10. The mixed UV-LED radiation curable protective varnish according to any one of claims 1-3, wherein the free radical photoinitiator is selected from the group consisting of α-hydroxy ketones, benzyl diketals, phenyl acetal esters, and mixtures thereof.

11. The hybrid 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 hybrid 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 / 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 in step i) is performed by a printing method selected from inkjet printing, flexographic printing and screen printing.

14. 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 / or a surface of the one or more security features, wherein the protective coating is obtained by the method of claim 12.

15. The secure document of claim 14, wherein the secure document is selected from banknotes, contracts, bills, checks, vouchers, tax stamps, tax labels, agreements, and identity documents.

16. The secure document of claim 14, wherein the secure document is selected from passports, ID cards, visas, bank cards, credit cards, transaction cards, travel documents, and admission tickets.

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