Method for making an overt security feature exhibiting one or more indicia - Patents.com

Abstract

The present invention relates to the field of methods for making eye-catching overt security features displaying one or more indicia as a means of preventing counterfeiting of valuable documents or articles as well as for decorative purposes. In particular, the present invention provides a method for making a security feature that can be easily, directly and unambiguously authenticated by a person without any external device or tool, said security feature comprising a cured ink and one or more cured indicia, said ink comprising a cured cationically curable compound or a cured hybrid curable compound and silver nanoplatelets.

Description

Detailed Description of the Invention

[0001] [Field of the Invention]

[0001] The present invention relates to the field of methods for producing security features on substrates, particularly value documents or articles. In particular, the present invention provides a method for producing an eye-catching, overt security feature that exhibits a first color when viewed in transmitted light and a second color, different from the first color, when viewed in incident light, and that exhibits one or more indicia on the value document or article as an anti-counterfeiting measure and for decorative purposes.

[0002] [Background of the invention]

[0002] With the ever-improving quality of color copying and printing, it has been conventional practice to incorporate various security features in an attempt to protect valuable documents such as banknotes, value documents or cards, transport tickets or cards, tax banderoles, and product labels without reproducible consequences against counterfeiting, falsifying, or illegal duplication.

[0003]

[0003] Security features, for example for valuable documents, can generally be classified on the one hand as "covert" security features and on the other hand as "overt" security features. The protection offered by covert security features rests on the notion that such features are difficult to detect and usually require specialized equipment and knowledge for detection, whereas "overt" security features rest on the notion that such features are easily detectable by unaided human senses, for example that such features are visible and / or detectable by touch, but are nevertheless difficult to make and / or copy. However, the effectiveness of overt security features depends heavily on their easy recognition as security features, since most users, especially those without prior knowledge of the security features of a document or item secured thereby, will only actually carry out a security check based on said security features once they have actually acquired knowledge of their existence and nature.

[0004]

[0004] A special role in securing valuable documents is played by dichroic security features that exhibit a first color when viewed in transmitted light and a second color different from the first color when viewed in incident light. To provide a striking effect and attract the public's attention, the first and second colors must have an attractive visual appearance, such as blue, metallic yellow, magenta, and green, and a significant color contrast (blue / metallic yellow, green / metallic yellow, violet / metallic yellow).

[0005]

[0005] Dichroic security features that exhibit a blue color in transmitted light and a metallic yellow color in incident light are obtained from inks that contain silver platelets.

[0006]

[0006] WO 2020 / 224982 discloses a composition comprising silver nanoplatelets, as well as a coating comprising said nanoplatelets and exhibiting a blue color in transmission and a metallic yellow color in reflection.

[0007]

[0007] WO 2020 / 083794 discloses a composition comprising silver nanoplatelets, as well as a coating comprising said nanoplatelets and exhibiting a red or magenta color in transmission and a greenish metallic color in reflection.

[0008]

[0008] WO 2021 / 213942 discloses a composition comprising platelet-shaped transition metal particles, as well as a coating comprising the particles and exhibiting a blue-green or blue color in transmission and a yellowish metallic color in reflection, or a red or magenta color in transmission and a greenish metallic color in reflection.

[0009]

[0009] WO 2021 / 214244 discloses a method for producing a security feature for securing a value document, the security feature exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light. The disclosed method includes the steps of: a) printing a specific UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a substrate of the value document; b) heating the ink layer obtained in step a) at a temperature of about 55°C to about 100°C for at least 1 second such that the ink layer exhibits a metallic yellow color when viewed in incident light; and c) UV-Vis curing the ink layer obtained in step b) to form the security feature.

[0010]

[0010] Co-pending European Patent Application No. 20206794.8 discloses a UV-Vis radiation curable security ink for producing a security feature that exhibits a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, the ink comprising silver nanoplatelets, a UV-Vis radiation curable compound, one or more cationic photoinitiators, a perfluoropolyether surfactant and a polyvinyl chloride copolymer.

[0011]

[0011] WO 2021 / 175907 discloses a UV-Vis radiation cationic curable security ink and a UV-Vis radiation curable hybrid security ink comprising an ink vehicle and a pigment comprising a flake-shaped non-metallic or metallic substrate comprising one or more at least partial coating layers, and at least a partial surface treatment layer made of one or more surface modifiers based on perfluoropolyether.

[0012]

[0012] Thus, there remains a need for a method of producing an eye-catching customized overt security feature comprising silver nanoplatelets and exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, particularly for demanding applications requiring high counterfeit resilience and excellent optical properties, where the method should be reliable, easy to implement and capable of running at high production rates. In particular, there is a need for a method of producing a customized overt security feature based on silver nanoplatelets and exhibiting one or more well resolved indicia using a solvent-free or low VOC-containing UV-Vis radiation curable ink, which is a cationic curable ink or a hybrid curable ink, where the security feature exhibits easily recognizable optical properties, particularly chroma contrast, thus allowing easy direct and unambiguous authentication by a person without any external device or tool.

[0013] [Summary of the Invention]

[0013] The object of the present invention is therefore to overcome the drawbacks of the prior art. This is achieved by providing a method for producing a security feature on a substrate (x20), said security feature exhibiting one or more indicia (x30), said method comprising the following steps: Step a) of applying a UV-Vis radiation curable ink to a surface of a substrate (x20) to form a coating layer (x10), said UV-Vis radiation curable ink being in a first liquid state, said UV-Vis radiation curable ink comprising: i) about 7.5 wt-% to about 20 wt-% of general formula (V) [ka] [In the formula, residue R A is a C2-C4 alkyl group substituted with a hydroxy group; residue R B is selected from C1-C4 alkyl groups, and C2-C4 alkyl groups substituted with hydroxy groups; Cat + is the general formula + NH2R C R D where R is the ammonium cation C is a C2-C4 alkyl group substituted with a hydroxy group, residue R D is selected from C1-C4 alkyl groups and C2-C4 alkyl groups substituted with hydroxy groups. silver nanoplatelets having a surface stabilizer; ii) about 45 wt-% to about 80 wt-% of a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds; iii) one or more cationic photoinitiators; iv) perfluoropolyether surfactants functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl; v) from about 3 wt-% to about 12 wt-% of a polyvinyl chloride copolymer containing at least 60 wt-% vinyl chloride; and optionally vi) up to about 25 wt-% of one or more organic solvents wherein the weight percentage is based on the total weight of the UV-Vis radiation curable ink; After step a), a step b) of at least partially applying a top-coating composition on the coating layer (x10) by a non-contact fluid microdispensing technique, said top-coating composition being applied in the form of one or more indicia (x30), said one or more indicia (x30) having a mass of about 0.8 g / m 2 More than 1.0 g / m 2 step b); After step b), a step c) of curing the coating layer (x10) and the one or more indicia (x30) in one or more curing units (x50), The time between steps b) and c) is less than 5 seconds, preferably less than about 4 seconds, and more preferably equal to or less than about 3.5 seconds.

[0014]

[0014] In one preferred embodiment, step a) of applying the UV-Vis radiation curable ink described herein is carried out by a printing process selected from the group consisting of a gravure printing process, a flexographic printing process and a screen printing process, preferably selected from the group consisting of a screen printing process.

[0015] In one preferred embodiment, step b) of applying the top coating composition is carried out by an inkjet printing process, preferably by a drop-on-demand inkjet printing process.

[0016]

[0016] Also described in this specification are security features made by the methods described in this specification, as well as value documents and value articles, and decorative elements and objects that include one or more security features described in this specification.

[0017]

[0017] Also described herein is a method for producing a document of value, an item of value, or a decorative element or object, comprising the steps of: a) preparing a document of value, an item of value, or a decorative element or object; and b) providing one or more security features, such as those described herein, and in particular those obtainable by the methods described herein, on or contained by the document of value, item of value, or decorative element or object.

[0018]

[0018] The method described herein advantageously uses two compositions, wherein said two compositions are applied wet-on-wet to each other, i.e. a top-coating composition described herein is applied at least partially on top of an applied UV-Vis radiation curable ink described herein, said composition still being at least partially unpolymerized. In particular, the method according to the invention allows the creation of an attention-grabbing overt security feature exhibiting one or more indicia in a universal manner and can be easily carried out at high production rates on an industrial scale. The two compositions used in the method described herein comprise as a first composition a UV-Vis radiation curable ink comprising silver nanoplatelets as described herein, applied to a substrate (x20) as described herein, and as a second composition a top-coating composition as described herein, said second composition being applied at least partially on top of the UV-Vis radiation curable ink and at least partially overlapping (i.e. overlapping in at least one area) said composition, said UV-Vis radiation curable ink being applied in the form of one or more indicia as described herein, while said UV-Vis radiation curable ink is still wet and at least partially unpolymerized. Upon curing of the UV-Vis radiation curable ink and top coating composition in the form of one or more indicia (x30), the so obtained overt security feature comprises a first area made of the cured covering layer (x10) devoid of the cured one or more inkjet printed indicia (x30) and a second well resolved area made of a combination of the cured covering layer (x10) and the one or more cured inkjet printed indicia (x30), said first and second areas exhibiting different optical properties in terms of saturation, thus allowing easy direct and unambiguous authentication of the overt security feature by a person without any external device or tool. [Brief description of the drawings]

[0019] [Figure 1]FIG. 1A shows a photograph of a substrate (120) including a security feature, said feature including a cured inkjet printed indicia (130) in the shape of the name "SICPA" in gradually decreasing font sizes, said security feature being prepared by a method according to the invention. The security feature includes a first area made of a cured coating layer (110) lacking the cured inkjet printed indicia (130) and a second area made of a combination of the cured coating layer (110) and the cured inkjet printed indicia (130), as viewed at an angle of about 0° under diffuse illumination. FIG. 1B shows for comparison purposes a photograph of a substrate (120) including a first area made of a cured coating layer (110) overprinted with the same indicia (130) as described for FIG. 1A, where said indicia is printed with a laser printer with a resolution of 600 dpi instead of inkjet printing. [Diagram 2] 2 shows a photograph of a substrate (220) including a security feature, said feature including a cured inkjet printed indicia (230) in the form of a QR code, said security feature being prepared by a method according to the present invention. The security feature includes a first area made of the cured coating layer (210) lacking the cured inkjet printed indicia (230) and a second area made of a combination of the cured coating layer (210) and the cured inkjet printed indicia (230), viewed at an angle of about 0° under diffuse lighting. [Figure 3A] FIG. 3A shows a table containing the experimentally determined and calculated top-coating inkjet ink coverage, and FIG. 3B shows the linear regression line obtained from the top-coating ink coverage in dpd (drops per dot) versus the inkjet ink coverage in g / m2 (measured by weight) as well as the linear function and R2-value. [Figure 3B] FIG. 3A shows a table containing the experimentally determined and calculated top-coating inkjet ink coverage, and FIG. 3B shows the linear regression line obtained from the top-coating ink coverage in dpd (drops per dot) versus the inkjet ink coverage in g / m2 (measured by weight) as well as the linear function and R2-value.

[0020] [Detailed Description] definition The following definitions are used to interpret the meaning of terms discussed in the specification and recited in the claims.

[0021] As used herein, the article "a" denotes one as well as more than one and does not necessarily limit the referent noun to the singular.

[0022] As used herein, the term "at least one" means one or more than one, for example, specifying one or two or three.

[0023]

[0022] As used herein, the term "about" means that the amount or value in question may be the specific value specified or another value nearby it. In general, the term "about" when describing a value is intended to indicate a range within ±5% of the value. As an example, the phrase "about 100" indicates a range of 100 ±5, i.e., a range of 95 to 105. Preferably, the range indicated by the term "about" indicates a range within ±3%, more preferably ±1% of the value. In general, when the term "about" is used, it can be expected that similar results or effects according to the present invention can be obtained within a range of ±5% of the indicated value.

[0024]

[0023] As used herein, the term "and / or" means that all or only one of the elements of a stated group may be present. For example, "A and / or B" means "A only, or B only, or both A and B." In the case of "A only," the term also encompasses the possibility that B is not present, i.e., "A only and not B."

[0025]

[0024] As used herein, the term "comprising" is intended to be non-exclusive and open-ended. Thus, for example, a solution containing compound A may contain other compounds in addition to A. However, the term "comprising" also encompasses the more restrictive meanings of "consisting essentially of" and "consisting of" in its specific embodiments, so that, for example, a "solution containing A, B, and optionally C" may consist (essentially) of A and B, or may consist (essentially) of A, B, and C.

[0026]

[0025] The terms "UV-Vis curable" and "UV-Vis curing" refer to radiation curing by photopolymerization under the influence of radiation having wavelength components in the UV or UV and visible portions of the electromagnetic spectrum (typically 100 nm to 800 nm, preferably 150 nm to 600 nm, more preferably 200 nm to 400 nm).

[0027]

[0026] In the context of the present invention, the term "(meth)acrylate" means an acrylate as well as the corresponding methacrylate. Similarly, "di(meth)acrylate" means a diacrylate as well as the corresponding dimethacrylate, and "tri(meth)acrylate" means a triacrylate as well as the corresponding trimethacrylate.

[0028]

[0027] The terms "document of value" and "item of value" generally refer to a document / item that is protected against counterfeiting or fraud by at least one security feature.

[0029] The term "security feature" is used to denote an image, pattern or graphic element that can be used for authentication purposes.

[0030]

[0029] When "preferred" embodiments / features are referred to in this specification, combinations of these "preferred" embodiments / features are also disclosed insofar as a particular combination of "preferred" embodiments / features makes technical sense.

[0031]

[0030] The method described herein allows the production of a security feature exhibiting one or more indicia (x30) and produced by the method described herein with the UV-Vis radiation curable inks described herein and the top coating compositions described herein. As mentioned above, the security feature produced by the method described herein comprises a first area made of a cured coating layer (x10) lacking one or more cured inkjet printed indicia (x30) and a second area made of a combination of the cured coating layer (x10) and one or more cured inkjet printed indicia (x30), whereby a good to good contrast is obtained between said areas, the first area exhibiting a blue color when viewed in transmitted light, i.e. in transmission, and a metallic yellow or gold color when viewed in incident light, i.e. in reflection, while the one or more indicia (x30) exhibit a brown color.

[0032] For the purposes of this invention, viewing in transmitted light means illuminating the security feature from one side, for example by holding the security feature facing sunlight or in front of a light source, and viewing it from the other side. A blue color is observed regardless of the side on which the security feature is viewed in transmitted light. For the purposes of this invention, an area exhibiting blue color is defined as an area having a chroma value C of greater than 20. * (corresponding to a measure of color intensity or color saturation). Intense to very intense blues are those with saturation values ​​C greater than 30. * It is characterized by the saturation value C * follows the CIELAB (1976) color space. * and b * It is calculated from the value, where

number

[0033]

[0032] The a in transmitted light * and b * The values ​​are measured using a Datacolor 650 spectrophotometer (parameters: integrating sphere, diffuse illumination (pulsed xenon D65) and 8° field of view, analyzer SP2000, dual 256 diode array, wavelength range 360-700 nm, transmitted light sampling aperture size 22 mm).

[0034]

[0033] In this patent application, the terms "metallic yellow" and "gold" are used synonymously. For the purposes of the present invention, "viewed with incident light" means illuminating the security feature from a surface containing the coating layer (x10) and one or more indicia (x30) described herein and viewed from the same side. For the purposes of the present invention, an area exhibiting a metallic yellow or gold color is a * and b * Chroma value C greater than 20 calculated from the value * (corresponding to a measure of color intensity or chroma (color saturation)), where

number

[0035]

[0034] The method described herein comprises a step a) of applying a UV-Vis radiation curable ink comprising nano-silver platelets as described herein to a surface of a substrate (x20) as described herein to form a coating layer (x10) as described herein, said composition being in a first liquid state allowing its application as a layer and not yet cured (i.e. wet). The UV-Vis radiation curable ink as described herein is to be provided on the surface of the substrate (x20), so that the UV-Vis radiation curable ink comprises one or more curable compounds and nano-silver platelets as described herein, said composition being in a form allowing its processing in a desired printing or coating equipment. Preferably, said step a) is carried out by a printing process, more preferably by a printing process selected from the group consisting of a screen printing process, a gravure printing process and a flexographic printing process, even more preferably by a screen printing process. Thus, the UV-Vis radiation curable ink is preferably selected from the group consisting of screen printing inks, gravure printing inks and flexographic printing inks, more preferably a screen printing ink, since said ink is particularly useful for the industrial production of security features on value documents, since it allows the printing at very high speeds of security features having a thickness of from about 2 μm to about 12 μm, preferably from about 3 μm to about 11, more preferably from about 3.5 μm to about 10 μm.

[0036]

[0035] Preferably, the UV-Vis radiation curable inks are characterized by a viscosity of from about 100 mPas to about 500 mPas at 25°C, preferably from about 150 mPas to about 350 mPas at 25°C, as measured using a Brookfield viscometer (model "DV-I Prime) equipped with spindle S21 at 100 rpm to measure viscosities of 500 mPas or less. The UV-Vis radiation curable coating screen printing compositions described herein are characterized by a viscosity of from about 100 mPas to about 500 mPas at 25°C, preferably from about 150 mPas to about 350 mPas at 25°C.

[0037]

[0036] As known to those skilled in the art, the term rotogravure printing refers to a printing process described, for example, in Handbook of Print Media, Helmut Kipphan, Springer Edition, page 48. Rotogravure printing is a printing process in which image elements are imprinted on the surface of a cylinder. The non-image areas are at a constant original level. Before printing, the entire printing plate (non-printing and printing elements) is inked and flooded with ink. The ink is removed from the non-image with a wiper or blade before printing, so that the ink remains only in the cells. The image is transferred from the cells to the substrate by pressure, usually in the range of 2-4 bar, and by the adhesive forces between the substrate and the ink. The term rotogravure printing does not include, for example, intaglio printing processes (also called in the art as imprinted steel die or copperplate printing processes), which rely on different types of ink.

[0038]

[0037] The flexographic printing process preferably uses a unit with a chambered doctor blade, an anilox roller and a plate cylinder. The anilox roller advantageously has small cells, the volume and / or density of which determine the ink or varnish application speed. The chambered doctor blade faces the anilox roller, filling the cells and at the same time scraping off excess ink or varnish. The anilox roller transfers the ink to the plate cylinder, which finally transfers the ink to the substrate. The plate cylinder can be made of polymeric or elastomeric materials. Polymers are mainly used as photopolymers in plate form and sometimes as seamless coatings on sleeves. Photopolymer plates are made of photosensitive polymers that are cured by ultraviolet (UV) light. The photopolymer plate is cut to the required 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 inverted, the negative of the job is placed on the uncured side and the plate is further exposed to UV light. This hardens the image areas of the plate. The plate is then processed to remove the uncured photopolymer from the non-image areas, lowering the plate surface in these non-image areas. After processing, the plate is dried and the entire plate is cured with a post-exposure dose of UV light. Preparation of plate cylinders for flexographic printing is described in Printing Technology, JMAdams and PADOlin, Delmar Thomson Learning, 5 th Edition, pages 359-360.

[0039] Screen printing (also known in the art as silk screen printing) is a printing technique that uses a screen, usually made of a woven mesh, to support an ink-blocking stencil. The attached stencil creates open areas of the mesh that transfer the ink onto the substrate as a sharp-edged image. A squeegee moves across the screen with the ink-blocking stencil, forcing the ink to pass through the woven mesh threads in the open areas. An important feature of screen printing is that it can apply a greater thickness of ink to the substrate than other printing techniques. Screen printing is therefore also preferred when ink deposits of thicknesses of about 10-50 μm or more are required that cannot be (easily) achieved by other printing techniques. Generally, screens are made of a piece of porous, finely woven fabric, called mesh, that is stretched over a frame, for example of aluminum or wood. Currently, most meshes are made of synthetic or man-made materials such as steel threads. The preferred synthetic materials are nylon or polyester threads.

[0040] In addition to screens made based on woven meshes based on synthetic or metal yarns, screens have been developed from solid metal sheets having a grid of holes. Such screens are prepared by a process which includes electrolytically forming a metal screen by forming a screen skeleton on a matrix containing a separating agent in a first electrolytic cell, stripping the formed screen skeleton from the matrix, and subjecting the screen skeleton to electrolysis in a second electrolytic cell to deposit metal on the skeleton.

[0041]

[0040] There are three types of screen printers: flatbed, cylinder and rotary screen printers. Flatbed and cylinder screen printers are similar in that they both use a flat screen and a three-step regression process to perform the printing operation. The screen is first moved into position above the substrate, then a squeegee is pressed against the mesh and pulled over the image area, and then the screen is lifted off the substrate to complete the process. In a flatbed press, the substrate to be printed is placed on a horizontal print bed, which is usually parallel to the screen. In a cylinder press, the substrate is mounted on a cylinder. Flatbed and cylinder screen printing processes are discontinuous processes and as a result are generally limited to a maximum of 45 m / min in web or 3'000 sheets / hour in sheet-fed processes.

[0042]

[0041] Rotary screen presses, on the other hand, are designed for continuous high-speed printing. The screens used in rotary screen presses are thin metal cylinders, for example usually obtained using the electroforming method described above or made of woven steel threads. The open cylinders are capped at both ends and fitted into blocks at the side of the press. During printing, ink is pumped into one end of the cylinder, so that a fresh supply is constantly maintained. A squeegee is fixed inside the rotating screen, and the squeegee pressure is maintained and adjusted to allow a good and constant printing quality. The advantage of rotary screen presses is the speed that can easily be achieved of 150 m / min in web or 10'000 sheets / hour in sheet-fed processes.

[0043] Screen printing is further described in, for example, The Printing Ink Manual, RH Less and RJ Pierce, Springer Edition, 5 th Edition, pages 58-62, Printing Technology, JMAdams and PADolin, Delmar Thomson Learning, 5th Edition, pages 293-328 and Handbook of Print Media, H. Kipphan, Springer, pages 409-422 and pages 498-499.

[0044] According to one embodiment, the UV-Vis radiation curable ink described herein is a UV-Vis radiation cationically curable ink. According to another embodiment, the UV-Vis radiation curable ink described herein is a UV-Vis radiation hybrid curable ink, i.e. an ink comprising one or more cationically curable compounds and one or more free radically curable compounds.

[0045]

[0044] The method described herein comprises a step c) of curing the coating layer (x10) and one or more indicia (x30); in other words, the UV-Vis radiation curable ink and topcoat compositions described herein are subjected to UV-Vis curing to form the security features described herein. As used herein, the term "UV-Vis curing" refers to radiation curing of an ink layer by photopolymerization under the influence of radiation having wavelength components in the UV or UV and visible parts of the electromagnetic spectrum (usually 100 nm to 800 nm, preferably 150 nm to 600 nm, more preferably 200 nm to 400 nm). Cationically curable monomers are cured by a cationic mechanism consisting of activation by UV-Vis light of one or more photoinitiators, which liberate cationic species, such as acids, which in turn initiate the polymerization of the compounds to form a cured layer. Radical curable monomers and oligomers are cured by a free radical mechanism consisting of the activation by UV-Vis light of one or more photoinitiators, which liberate free radicals that then start the polymerization process. Optionally, one or more photosensitizers may also be present. The photosensitizer is activated by one or more of the wavelengths emitted by the UV-Vis light source to reach an excited state. The excited photosensitizer transfers energy to one or more photoinitiators (in the case of radical polymerization) or electrons (in the case of cationic polymerization). Either process then starts the polymerization process.

[0046] Suitable UV-Vis radiation cationic or hybrid curable inks are described in co-pending European Patent Application No. 20206794.8.

[0047]

[0046] The UV-Vis radiation curable inks described herein comprise from about 45 wt-% to about 80 wt-% of a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds. The one or more UV-Vis radiation curable compounds may comprise one or more cationically curable monomers (cationically curable inks) or comprise one or more cationically curable and one or more radically curable monomers and / or oligomers (hybrid inks). If the UV-Vis radiation cationic curable inks described herein comprise a mixture of from about 45 wt-% to about 80 wt-% of a cycloaliphatic epoxide and one or more cationically curable monomers, it is preferred that the ratio of the total weight percentage (wt-%) of the one or more cationically curable monomers to the weight percentage (wt-%) of the cycloaliphatic epoxide is lower than 1.4:1, preferably lower than 1:1, more preferably lower than 0.9:1.

[0048]

[0047] If the one or more UV-Vis radiation curable compounds comprise one or more radically curable compounds (i.e. comprise a hybrid ink), the UV-Vis radiation curable ink described herein further comprises one or more free radical photoinitiators.

[0049]

[0048] An alternative preferred embodiment relates to a UV-Vis radiation hybrid curable ink (i.e. an ink comprising both cationically curable and radically curable monomers / oligomers) for producing the security features described herein, said ink comprising from about 45 wt-% to about 80 wt-% of a mixture of cycloaliphatic epoxide and one or more radically curable monomers and / or oligomers; or from about 45 wt-% to about 80 wt-%, preferably from about 45 wt-% to about 65 wt-%, of a mixture of cycloaliphatic epoxide, one or more cationically curable monomers and one or more radically curable monomers and / or oligomers. If the hybrid inks described herein comprise a mixture of about 45 wt-% to about 80 wt-% of a cycloaliphatic epoxide and one or more radically curable monomers and / or oligomers, the ratio of the total weight percent (wt-%) of the one or more radically curable monomers and / or oligomers to the weight percent (wt-%) of the cycloaliphatic epoxide is preferably less than 1.6:1, more preferably less than 1:1, and even more preferably less than 0.5:1. If the hybrid inks described herein comprise a mixture of about 45 wt-% to about 80 wt-% of a cycloaliphatic epoxide, one or more cationically curable monomers, and one or more radically curable monomers and / or oligomers, the ratio of the total weight percentage (wt-%) of the one or more radically curable monomers and / or oligomers to the sum of the weight percentage (wt-%) of the cycloaliphatic epoxide and the total weight percentage (wt-%) of the one or more cationically curable monomers is preferably lower than 1.6:1, more preferably lower than 1:1, and even more preferably lower than 0.5:1, and the ratio of the weight percentage (wt-%) of the one or more cationically curable monomers to the weight percentage (wt-%) of the cycloaliphatic epoxide is preferably lower than 1.4:1, more preferably lower than 1:1, and even more preferably lower than 0.9:1.

[0050] As known to those skilled in the art, cycloaliphatic epoxides contain at least a substituted or unsubstituted epoxycyclohexyl residue: [ka] It is a cationic curable monomer containing

[0051]

[0050] The cycloaliphatic epoxide(s) described herein may be difunctional or polyfunctional. Preferably, the cycloaliphatic epoxide(s) described herein contain at least one cyclohexane ring and at least two epoxide groups. More preferably, the cycloaliphatic epoxide has the general formula (I): [ka] [wherein -L- represents a single bond or a divalent group containing one or more atoms]. The alicyclic epoxide of general formula (I) may be optionally substituted with 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, s-butyl, t-butyl, hexyl, octyl, and decyl), preferably alkyl groups containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl).

[0052] In general formula (I), the divalent group -L- can be a linear or branched alkylene group containing 1 to 18 carbon atoms. Examples of the linear or branched alkylene group include, without limitation, methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene groups.

[0053] In general formula (I), the divalent group -L- can be a divalent alicyclic hydrocarbon group or a cycloalkydene group, such as 1,2-cyclopentylene, 1,3-cyclopentylene, cyclopentylidene, 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, and cyclohexylidene.

[0054] In the general formula (I), -L- can be a divalent radical containing one or more oxygen-containing linking groups, said oxygen-containing linking groups being selected from the group consisting of -C(-O)-, -OC(=O)O-, -C(=O)O-, and -O-. Preferably, the cycloaliphatic epoxide is of the general formula (II), in which -L- is a divalent radical containing one or more oxygen-containing linking groups, said oxygen-containing linking groups being selected from the group consisting of -C(=O)-, -OC(=O)O-, -C(=O)O-, and -O-, more preferably of the general formula (II-a), (II-b), or (II-c) as defined below. [ka] [In the formula, L 1 may be the same or different in 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); L 2 may be the same or different in 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); l1 and l2 each independently represent an integer of 0 to 9, preferably 0 to 3; [ka] [In the formula, L 1may be the same or different in each occurrence and are linear or branched alkyl groups 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); L 2 may be the same or different in each occurrence and are linear or branched alkyl groups 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); l1 and l2 each independently represent an integer of 0 to 9, preferably an integer of 0 to 3; -L 3 - is a single bond or a linear or branched divalent hydrocarbon radical containing 1 to 10 carbon atoms, preferably 3 to 8 carbon atoms, such as alkylene radicals, e.g., trimethylene, tetramethylene, hexamethylene, and 2-ethylhexylene, and cycloalkylene radicals, e.g., 1,2-cyclohexylene, 1,3-cyclohexylene, and 1,4-cyclohexylene, and cyclohexylidene; [ka] [In the formula, L 1 may be the same or different in 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; L 2 may be the same or different in 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; l1 and l2 each independently represent an integer of 0 to 9, preferably an integer of 0 to 3.

[0055] Preferred alicyclic epoxides of general formula (II-a) include, but are not limited to: 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methyl-cyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, 3,4-epoxy-2-methyl-cyclohexylmethyl-3,4-epoxy-2-methyl-cyclohexanecarboxylate, and 3,4-epoxy-4-methyl-cyclohexylmethyl-3,4-epoxy-4-methylcyclohexanecarboxylate.

[0056]

[0055] Preferred alicyclic epoxides of general formula (II-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.

[0057] A preferred cycloaliphatic epoxide of general formula (II-c) is 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane.

[0058]

[0057] Further alicyclic epoxides include alicyclic epoxides of general formula (III-a) and alicyclic epoxides of general formula (III-b), which may optionally be substituted with 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, s-butyl, t-butyl, hexyl, octyl, and decyl), preferably those containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl). [ka]

[0059] The cycloaliphatic epoxides described herein may be hydroxy- or (meth)acrylate-modified. Examples are sold by Daicel Corp. under the names Cyclomer A400 (CAS: 64630-63-3) and Cyclomer M100 (CAS number: 82428-30-6), or by TetraChem / Jiangsu under the names TTA 15 and TTA16 46.

[0060]

[0059] The one or more UV-Vis radiation curable compounds, which are cationically curable monomers as described herein, are preferably selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers other than cycloaliphatic epoxides, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl-containing compounds, and mixtures thereof, preferably from the group consisting of vinyl ethers, cyclic ethers other than cycloaliphatic epoxides, and mixtures thereof. Cyclic ethers other than cycloaliphatic epoxides include epoxides other than cycloaliphatic epoxides, oxetanes, and tetrahydrofurans. Preferably, the ratio of the total weight percentage (wt-%) of the one or more cationically curable monomers to the weight percentage (wt-%) of the cycloaliphatic epoxide is lower than 1.4:1, more preferably lower than 1:1, most preferably lower than 0.9:1, and especially preferably lower than 0.8:1.

[0061]

[0060] Vinyl ethers are known in the art to accelerate curing and reduce tackiness, thus limiting the risk of blocking and set-off when printed sheets are stacked immediately after printing and curing. They also improve the physical and chemical resistance of the printed security features and increase the flexibility of the printed and cured ink layer and its adhesion to the substrate, which is particularly advantageous for printing plastic and polymeric substrates. Vinyl ethers also help to reduce the viscosity of the ink while copolymerizing tightly with said ink. Examples of preferred vinyl ethers for use in the security inks described herein include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, ethylhexyl vinyl ether, octadecyl vinyl ether, dodecyl vinyl ether, isopropyl vinyl ether, tert-butyl vinyl ether, tert-amyl vinyl ether, cyclohexyl vinyl ether, cyclohexanedimethanol monovinyl ether, cyclohexanedimethanol divinyl ether, 4-(vinyloxymethyl)cyclohexylmethyl benzoate, phenyl vinyl ether, methylphenyl vinyl ether, methoxyphenyl vinyl ether, 2-chloroethyl vinyl ether, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, 1,6-hexanediol monovinyl ether, ethylene glycol divinyl ether, ethylene glycol monovinyl ether, 1,4-butanediol divinyl ether, 1,6-Hexanediol divinyl ether, 4-(vinyloxy)butyl benzoate, bis[4-(vinyloxy)butyl]adipate, bis[4-(vinyloxy)butyl]succinate, bis[4-(vinyloxymethyl)cyclohexylmethyl]glutarate, 4-(vinyloxy)butyl stearate, trimethylolpropane trivinyl ether, propenyl ether of propylene carbonate, diethylene glycol monovinyl ether, diethylene glycol divinyl ether, ethylene glycol butyl vinyl ether, dipropylene glycol divinyl ether, triethylene glycol divinyl ether, triethylene glycol Examples of suitable vinyl ethers include ethylene glycol methyl vinyl ether, triethylene glycol monobutyl vinyl ether, tetraethylene glycol divinyl ether, poly(tetrahydrofuran) divinyl ether, polyethylene glycol-520 methyl vinyl ether, Prolyol-E200 divinyl 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, and bis[4-(vinyloxy)methyl]cyclohexyl]methyl]isophthalate. Suitable vinyl ethers are marketed by BASF under the names EVE, IBVE, DDVE, ODVE, BDDVE, DVE-2, DVE-3, CHVE, CHDM-di, and HBVE. The vinyl ether or ethers described herein may be hydroxy-modified or (meth)acrylate-modified (e.g., VEEA, 2-(2-vinyloxyethoxy)ethyl acrylate (CAS: 86273-46-3) from Nippon Shokubai).

[0062]

[0061] Oxetanes are known in the art to accelerate curing and reduce tackiness, thus limiting the risk of blocking and set-off when printed sheets are stacked immediately after printing and curing, and also help to copolymerize strongly with the ink while reducing the viscosity of the ink. Preferred examples of oxetanes include trimethylene oxide, 3,3-dimethyloxetane, trimethylolpropaneoxetane, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-[(2-ethylhexyloxy)methyl]oxetane, 3,3-dicyclomethyloxetane, 3-ethyl-3-phenoxymethyloxetane, bis([1-ethyl(3-oxetanyl)]methyl)ether, 1,4-bis[3-ethyl-3-oxetanylmethoxy)methyl]benzene, 3,3-dimethyl-2(4-methoxy-phenyl)-oxetane, 3-ethyl-[(tri-ethoxysilylpropoxy)methyl]oxetane, 4,4-bis(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl and 3,3-dimethyl-2(p-methoxy-phenyl)oxetane. One or more of the oxetanes described herein may be hydroxy-modified or (meth)acrylate-modified (for example: UVi-Cure S170 (CAS: 37674-57-0) from Arkema (formerly Lambson)).

[0063]

[0062] The proper balance of one or more vinyl ethers described herein and one or more oxetanes described herein within the specified ranges helps to optimize the desired properties of the security features made of the UV-Vis radiation curable inks described herein, especially easy processability (optimum viscosity, fast cure, no set-off, no blocking) and strong chemical and physical resistance. Moreover, it also helps to increase cost-effectiveness since vinyl ethers and oxetanes are usually cheaper than cycloaliphatic epoxide compounds.

[0064]

[0063] The use of epoxides in the UV-Vis radiation curable inks described herein helps to accelerate cure, reduce tackiness, and reduce the viscosity of the ink while strongly copolymerizing with the ink. Preferred examples of epoxides other than the cycloaliphatic epoxides described herein include, but are not limited to, cyclohexanedimethanol 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-ethyl-hexyl 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 cycloaliphatic epoxides are sold under the trademark Grilonit® (e.g. Grilonit® V51-63 or RV 1806) by EMS Griltech.

[0065]

[0064] The radically curable monomers described herein are preferably selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, and mixtures thereof, preferably from the group consisting of tri(meth)acrylates, tetra(meth)acrylates, and mixtures thereof. In the context of the present invention, the term "(meth)acrylate" refers to the acrylates as well as the corresponding methacrylates.

[0066]

[0065] 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 trimethylolpropaneformal(meth)acrylate, nonylphenol(meth)acrylate, isobornyl(meth)acrylate, isodecyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, octyldecyl ... Examples of suitable di(meth)acrylates include butyl di(meth)acrylate, tridecyl di(meth)acrylate, methoxypoly(ethylene glycol) (meth)acrylate, polypropylene glycol (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 1,3-butylene glycol 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)acrylates, ester diol di(meth)acrylates, and mixtures thereof.

[0067]

[0066] Preferred examples of di(meth)acrylates include bisphenol A di(meth)acrylate, alkoxylated (e.g., ethoxylated and propoxylated) bisphenol A di(meth)acrylate, bisphenol A diglycidyl ether di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, and mixtures thereof.

[0068]

[0067] Preferred examples of tri(meth)acrylates include trimethylolpropane tri(meth)acrylate, alkoxylated (e.g., ethoxylated and propoxylated) trimethylolpropane tri(meth)acrylate, alkoxylated (e.g., ethoxylated and propoxylated) glycerol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, alkoxylated pentaerythritol tri(meth)acrylate, alkoxylated (e.g., ethoxylated and propoxylated) pentaerythritol tri(meth)acrylate, and mixtures thereof.

[0069]

[0068] Preferred examples of tetra(meth)acrylates include ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, alkoxylated (e.g., ethoxylated and propoxylated) pentaerythritol tetra(meth)acrylate, and mixtures thereof, preferably selected from the group consisting of ditrimethylolpropane tetra(meth)acrylate, alkoxylated pentaerythritol tetra(meth)acrylate, and mixtures thereof.

[0070]

[0069] As used herein, the term "radically curable oligomer" refers to a radically curable (meth)acrylate oligomer, which may be branched or linear in nature and may have terminal and / or pendant (meth)acrylate functional group(s). Preferably, the radically curable oligomer is selected from the group consisting of (meth)acrylic oligomers, urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether-based (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof, more preferably selected from the group consisting of polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof.

[0071] Suitable examples of epoxy (meth)acrylate oligomers include, without limitation, aliphatic epoxy (meth)acrylate oligomers, particularly mono(meth)acrylate, di(meth)acrylate and tri(meth)acrylate, and aromatic epoxy (meth)acrylate oligomers.Suitable examples of aromatic epoxy (meth)acrylate oligomers include bisphenol-A (meth)acrylate oligomers, such as bisphenol-A mono(meth)acrylate, bisphenol-A di(meth)acrylate and bisphenol-A tri(meth)acrylate, and alkoxylated (e.g., ethoxylated and propoxylated) bisphenol-A (meth)acrylate oligomers, such as alkoxylated bisphenol-A mono(meth)acrylate, alkoxylated bisphenol-A di(meth)acrylate and alkoxylated bisphenol-A tri(meth)acrylate, preferably alkoxylated bisphenol-A di(meth)acrylate.

[0072]

[0071] For embodiments in which the UV-Vis radiation curable ink described herein is a cationically curable ink (i.e., a fully cationically curable ink that does not contain any radically curable compounds), the compositions described herein preferably comprise from about 1 wt-% to about 10 wt-%, more preferably from about 1.1 wt-% to about 8 wt-%, and even more preferably from about 1.1 wt-% to about 6 wt-% of one or more cationic photoinitiators (also referred to in the art as photoacid generators), the weight percentages being based on the total weight of the UV-Vis radiation cationically curable ink. The one or more cationic photoinitiators described herein are onium salts, preferably selected from the group consisting of azonium salts, oxonium salts, iodonium salts, sulfonium salts, and mixtures thereof, more preferably selected from the group consisting of oxonium salts, iodonium salts, sulfonium salts, and mixtures thereof, and even more preferably selected from the group consisting of sulfonium salts, iodonium salts, and mixtures thereof.

[0073]

[0072] The one or more iodonium salts described herein have a cationic moiety and an anionic moiety, where the anionic moiety is preferably BF4 - , B(C6F5)4 - , PF6 - , AsF6 - , SbF6 - or CF3SO3 - , more preferably SbF6 - or PF6 - and even more preferably PF6 - wherein the cationic moiety is preferably an aromatic iodonium ion, more preferably an iodonium ion containing two aryl groups, the two aryl groups being optionally independently substituted with one or more alkyl groups (e.g., methyl, ethyl, isobutyl, tertbutyl, etc.), one or more alkoxy groups, one or more nitro groups, one or more halogen-containing groups, one or more hydroxy groups, or combinations thereof.

[0074] Iodonium salts particularly suitable for the present invention are commercially known and available under the names DEUTERON UV 1240, DEUTERON UV 1242, DEUTERON UV 2257, DEUTERON UV 1250, and DEUTERON UV 3100 (all available from DEUTERON), OMNICAT 250, OMNICAT 440, and OMNICAT 445 (all available from IGM Resins), SpeedCure 937, SpeedCure 938 and SpeedCure 939 (all available from Arkema (formerly Lambson)).

[0075]

[0074] One or more of the sulfonium salts described herein have a cationic moiety and an anionic moiety, where the anionic moiety is preferably BF4 - , B(C6F5)4 - , PF6 - , (PF 6-h (C j F 2j-1 ) h ) -(wherein h is an integer from 1 to 5, and j is an integer from 1 to 4), AsF6 - , SbF6 - , CF3SO3 - , perfluoroalkylsulfonates or pentafluoro-hydroxyantimonates, more preferably SbF6 - wherein the cationic moiety is preferably an aromatic sulfonium ion, more preferably a sulfonium ion containing two or more aryl groups, the two or more aryl groups being independently optionally substituted with one or more alkyl groups (e.g., methyl, ethyl, isobutyl, tertbutyl, etc.), one or more alkoxy groups, one or more aryloxy groups, one or more halogen-containing groups, one or more hydroxy groups, or combinations thereof. Suitable examples of sulfonium ions containing two or more aryl groups include, without limitation, triarylsulfonium ion, diphenyl[4-(phenylthio)phenyl]sulfonium ion, bis[4-(diphenylsulfonio)phenyl]sulfonium ion, triphenylsulfonium ion, and tris[4-(4-acetylphenyl)sulfanylphenyl]sulfonium ion. Particularly suitable examples of sulfonium salts for the present invention are those commercially available under the designations SpeedCure 976, SpeedCure 976D, SpeedCure 976S and SpeedCure 992, all available from Arkema (formerly Lambson); ESACURE 1187, OMNICAT 270, OMNICAT 320, OMNICAT 432 and OMNICAT 550, all available from IGM Resins; DoubleCure 1176, DoubleCure 1190 and DoubleCure 1172, all available from DoubleBond.

[0076]

[0075] Other examples of useful cationic photoinitiators can be found in standard textbooks, such as "Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints", Volume III, "Photoinitiators for Free Radical Cationic and Anionic Polymerization", 2nd edition, by JV Crivello & K. Dietliker, edited by G. Bradley and published in 1998 by John Wiley & Sons in association with SITA Technology Limited.

[0077] For embodiments in which the UV-Vis radiation curable ink described herein is a hybrid curable ink (i.e., an ink containing both cationically curable and radically curable compounds), the compositions described herein include one or more free radical photoinitiators. Preferably, the amount of one or more free radical photoinitiators in the UV-Vis radiation hybrid curable ink described herein is from about 1 wt-% to about 6 wt-%, the percentages being based on the total weight of the UV-Vis radiation hybrid curable ink.

[0078]

[0077] The one or more free radical photoinitiators are preferably selected from the group consisting of hydroxyketones (e.g., alpha-hydroxyketones), alkoxyketones (e.g., alpha-alkoxyketones), acetophenones, benzophenones, ketosulfones, benzil ketals, benzoin ethers, phosphine oxides, phenylglyoxylates, thioxanthones, and mixtures thereof, more preferably selected from the group consisting of phosphine oxides, hydroxyketones, thioxanthones, and mixtures thereof.

[0079] Suitable alpha-hydroxy ketones include, without limitation, (1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one), 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-hydroxy-2-methyl-1-(4-tert-butyl)phenylpropan-1-one, 2-hydroxy-1-[4-[[4-(2-hydroxy-2-methylpropanoyl)phenyl]methyl]phenyl]-2-methylpropan-1-one, 2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropanoyl)phenoxy]phenyl]-2-methylpropan-1-one, and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].

[0080] Suitable acetophenones include, without limitation, 2,2-diethoxyacetophenone, and 2-methoxy-2-phenylacetophenone.

[0081] Suitable benzophenones include, without limitation, benzophenone, polymeric benzophenone derivatives, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-phenylbenzophenone, 4-chlorobenzophenone, methyl-2-benzoylbenzoate, 4-(4-methylphenylthio)benzophenone, 4-hydroxybenzophenone laurate, and a mixture of 50% benzophenone and 50% 1-hydroxycyclohexyl phenyl ketone.

[0082] Suitable ketosulfones include, without limitation, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one.

[0083] Suitable benzyl ketals include, without limitation, 2,2-dimethoxy-2-phenylacetophenone.

[0084] Suitable benzoin ethers include, without limitation, 2-ethoxy-1,2-diphenylethanone, 2-isopropoxy-1,2-diphenylethanone, 2-isobutoxy-1,2-diphenylethanone, 2-butoxy-1,2-diphenylethanone, 2,2-dimethoxy-1,2-diphenylethanone, and 2,2-diethoxyacetophenone.

[0085] Suitable phosphine oxides include, without limitation, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethylphenyl(2,4,6-trimethylbenzoyl)phenylphosphinate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, substituted acyl-phosphine oxides, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and 2- mixtures of hydroxy-2-methypropiophenone, mixtures of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-hydroxy-2-methylpropiophenone, mixtures of ethyl(2,4,6-trimethylbenzoyl)phenylphosphineate and 2-hydroxy-2-methylpropiophenone, and mixtures of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and ethylphenyl(2,4,6-trimethylbenzoyl)phenylphosphineate.

[0086] Suitable thioxanthones include, without limitation, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 1-chloro-4-propoxythioxanthone, and polymeric thioxanthone derivatives.

[0087]

[0086] Suitable phenyl glyoxylates include, without limitation, methyl benzoyl formate, 2-[2-oxo-2-phenyl-acetoxy-ethoxy]ethyl 2-oxo-2-phenylacetate, and mixtures of 2-[2-oxo-2-phenyl-acetoxy-ethoxy]ethyl 2-oxo-2-phenylacetate and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester.

[0088]

[0087] Preferably, the one or more free radical photoinitiators are phosphine oxides as described herein, more preferably a mixture of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and ethylphenyl(2,4,6-trimethylbenzoyl)phenylphosphineate.

[0089] To increase reactivity and / or improve handling (e.g. by replacing a solid photoinitiator with a liquid blend), any blend of the free radical photoinitiators described herein may be used, such as, for example: a blend of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenylpropan-1-one, for example sold under the trade name Omnirad 4265 by IGM Resins; a blend of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate and 2-hydroxy-2-methylpropiophenone, for example sold under the trade name Omnirad 2022 by IGM Resins; a blend of ethyl(2,4,6-trimethylbenzoyl)phenylphosphineate and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, for example sold under the trade name Omnirad 2100 by IGM Resins; a blend of 2-hydroxy-2-methylpropiophenone and 1-hydroxycyclohexyl phenyl ketone sold under the trade name Omnirad 1000 by IGM Resins; a blend of oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] and 2-hydroxy-2-methylpropiophenone sold under the trade name Esacure KIP100F by IGM Resins; a blend of 2-hydroxy-2-methylpropiophenone, ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] sold under the trade name Omnirad BL 723 by IGM Resins; and a blend of 2-hydroxy-2-methylpropiophenone, ethyl (2,4,6-trimethylbenzoyl)phenylphosphinate and oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone] sold under the trade name Omnirad BL 723 by IGM Resins. and a blend of 2-hydroxy-2-methylpropiophenone, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone], ethyl(2,4,6-trimethylbenzoyl) and 2,2-dimethoxy-1,2-diphenylethan-1-one sold under the tradename No. 724.

[0090]

[0089] The UV-Vis radiation curable ink described herein contains d) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl, preferably two or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl. The perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl comprises a perfluoropolyether backbone and one or more, preferably two or more, terminal functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl, and is characterized by an average molecular weight (Mn) of less than about 2000 [g / mol]. As used herein, perfluoropolyether backbone refers to the residue of a perfluoropolyether polymer containing randomly distributed repeat units selected from perfluoromethyleneoxy (-CF2O-) and perfluoroethyleneoxy (-CF2-CF2O-). The perfluoropolyether residue may be fluorinated directly or at the carbon atom that connects the perfluoropolyether residue to the terminal functional group, which may be methylene(oxyethylene), 1,1-difluoroethylene-(oxyethylene), methylene-di(oxyethylene), 1,1-difluoroethylene-di(oxyethylene), methylene-tri(oxyethylene), 1,1-difluoroethylene-tri(oxyethylene), methylene-tetra(oxyethylene), 1,1-difluoroethylene-tetra(oxyethylene), methylene-penta(oxyethylene), 1,1-difluoroethylene-penta(oxyethylene), and optionally a spacer, selected from one or more urethane groups, or one or more amide groups, and optionally one or more cyclic moieties, such as linear or branched hydrocarbon groups containing saturated cyclic moieties (e.g., cyclohexylene) and aromatic cyclic moieties (e.g., phenylene). Preferably, the perfluoropolyether surfactant is functionalized with one or more hydroxyl functional groups.

[0091] In a further preferred embodiment, the perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl is a compound of general formula (IV) having an average molecular weight of about 1200 [g / mol] to about 2000 [g / mol] [ka] [In the formula, f and e are, independently of one another, integers selected from 1, 2, and 3; FG 1 and F.G. 2 are each independently -OH, -OC(O)CH=CH2, -OC(O)C(CH3)=CH2, and -Si(OR 20 a terminal functional group selected from the group consisting of: R 20 is a C1-C4 alkyl group; -S 1 - is a single bond or [ka] represents a spacer selected from Where: -J 1 -teeth [ka] is selected from where j 1 is an integer of 1 to 12, preferably 4 to 10; L 5are each the same or different and are linear or branched alkyl groups 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); L 6 are each the same or different and are linear or branched alkyl groups 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); l 5 and l 6 are each independently an integer of 0 to 4, preferably 0 to 1; -J 3 - is selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-; -J 2 -teeth [ka] is selected from a is an integer of 1 to 6, preferably 1 to 3; b is an integer of 1 to 6, preferably 2 to 4; -S 2 - is a single bond or [ka] represents a spacer selected from where -J 4 -teeth [ka] is selected from where j 4is an integer of 1 to 12, preferably 4 to 10; L 7 are each the same or different and are linear or branched alkyl groups containing 1 to 10 carbon atoms (e.g., methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, hexyl, octyl, decyl), preferably containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); L 8 are each the same or different and are linear or branched alkyl groups 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); l 7 and l 8 are each independently an integer of 0 to 4, preferably 0 to 1; -J 6 - is selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-; -J 5 -teeth [ka] is selected from r is an integer of 1 to 6, preferably 1 to 3; w is an integer of 1 to 6, preferably 2 to 4; and s and t are integers such that the average molecular weight of the compound of general formula (IV) is about 1200 [g / mol] to about 2000 [g / mol].

[0092] Preferably, in formula (IV), FG 1 and F.G. 2 represent, independently of each other, -OC(O)CH=CH2 or -OC(O)C(CH3)=CH2; -S 1 -teeth [ka] where b has the meaning defined herein; -S 2 -teeth [ka] where w has the meaning defined herein. Also preferably, in the general formula (IV), FG 1 and F.G. 2 represents -OH; -S 1 - is a single bond or [ka] where a has the meaning defined herein; -S 2 - is a single bond or [ka] where r has the meaning defined herein; The sum of o and r is 3 to 9.

[0093] Also preferably, in formula (IV), FG 1 and F.G. 2 -Si(OR 20 )3; R 20 is a C1-C4 alkyl group, preferably an ethyl group; -S 1 -teeth [ka] where b has the meaning defined herein; -S 2 -teeth [ka] where w has the meaning defined herein. Thus, preferred perfluoropolyether surfactants are compounds of the general formula (IV-a) [ka] [In the formula, b and w each represent an integer of 1 to 6, preferably an integer of 2 to 4; s is an integer from 2 to 6; and q is an integer from 2 to 4.

[0094]

[0093] Particularly suitable examples of perfluoropolyether surfactants functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate and trialkoxysilyl for the present invention are commercially available from Solvay under the names Fluorolink® E10H, Fluorolink® MD700, Fluorolink® AD1700, Fluorolink® E-series, and Fluorolink® S10.

[0095] The UV-Vis radiation curable inks described herein comprise from about 3 wt-% to about 12 wt-% of a polyvinyl chloride copolymer containing at least 60 wt-% vinyl chloride, preferably at least 63 wt-% vinyl chloride. Preferably, the polyvinyl chloride copolymer contains up to 90 wt-% vinyl chloride. Preferably, the polyvinyl chloride copolymer containing at least 60 wt-% vinyl chloride is present in the inks described herein in an amount of from about 4.9 wt-% to about 11.6 wt-%, most preferably from about 6 wt-% to about 8.6 wt-%, the weight percentages being based on the total weight of the UV-Vis radiation curable ink.

[0096]

[0095] Preferably, the polyvinyl chloride copolymer is selected from the group consisting of vinyl chloride-vinyl acetate copolymer, vinyl chloride-hydroxyalkyl acrylate copolymer, such as vinyl chloride-2-hydroxypropyl acrylate copolymer, and vinyl chloride-hydroxyalkyl acrylate-Z-alkylenedioic acid, dialkyl ester copolymer, such as vinyl chloride-2-hydroxypropyl acrylate-2-butenedioic acid (Z)-, dibutyl ester copolymer. The polyvinyl chloride copolymer preferably has a molecular weight of 3.0 or less as determined by size exclusion chromatography using polystyrene as standard and tetrahydrofuran as solvent. * 10 4 g / mol~about 8 * 10 4 Particularly suitable examples of polyvinyl chloride copolymers for the present invention are commercially available from Wacker under the names Vinnol® H14 / 36, Vinnol® E22 / 48A, Vinnol® E15 / 40A and Vinnol® H40 / 50.

[0097] The UV-Vis radiation curable inks described herein may contain up to about 25 wt-% of one or more organic solvents, where the weight percentage is based on the total weight of the UV-Vis radiation curable ink. The one or more solvents have a boiling point greater than 100° C. Suitable organic solvents for use in the UV-Vis radiation curable inks described herein include, without limitation: ethyl-3-ethoxypropionate, 2-methoxy-1-methylethyl acetate, propylene glycol monomethyl ether, cyclopentanone, cyclohexanone, n-butanol, cyclohexanol, ethylene carbonate, propylene carbonate, butylene carbonate, and mixtures thereof.

[0098]

[0097] The UV-Vis radiation curable inks described herein may further comprise one or more photosensitizers together with one or more photoinitiators described herein to achieve efficient curing. Suitable examples of photosensitizers are known to those skilled in the art (e.g., Industrial Photoinitiators, WAGreen, CRC Press, 2010, Table 8.1 p.170). Preferred photosensitizers are those that can achieve efficient and fast curing under UV-LED light sources, such as thioxanthone derivatives, anthracene derivatives, naphthalene derivatives and titanocene derivatives (e.g., Omnirad 784 sold by IGM Resins). Particularly preferred are thioxanthone and anthracene derivatives and mixtures thereof, including, without limitation, isopropyl-thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX), 2,4-diethyl-thioxanthone (DETX), 9,10-diethoxyanthracene (e.g., sold as Anthracure UVS-1101 by Kawasaki Kasei Chemicals Ltd), and 9,10-dibutyloxyanthracene (e.g., sold as Anthracure UVS-1331 by Kawasaki Kasei Chemicals Ltd). Alternatively, the thioxanthone photosensitizers may be used in oligomeric or polymeric form (e.g., Omnipol TX sold by IGM Resins, Genopol TX sold by Rahn, etc.). * TX-2, or Speedcure 7010 sold by Arkema (formerly Lambson). When present, the photosensitizer(s) are preferably present in an amount of about 0.1 wt-% to about 2 wt-%, more preferably about 0.2 wt-% to about 1 wt-%, the weight percentages being based on the total weight of the UV-Vis radiation curable ink.

[0099]

[0098] The UV-Vis radiation curable inks described herein may further contain one or more antifoaming agents in an amount of less than about 2 wt-%, preferably less than about 1 wt-%, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

[0100] The UV-Vis radiation curable inks described herein comprise from about 7.5 wt-% to about 20 wt-%, preferably from about 7.5 wt-% to about 15 wt-%, more preferably from about 10 wt-% to about 13 wt-% of silver nanoplatelets, wherein the silver nanoplatelets are represented by the general formula (V): [ka] [In the ceremony residue R A is a C2-C4 alkyl group substituted with a hydroxy group; residue R B is selected from C1-C4 alkyl groups, and C2-C4 alkyl groups substituted with hydroxy groups; Cat + is the general formula + NH2R C R D is the ammonium cation, where residue R C is a C2-C4 alkyl group substituted with a hydroxy group; residue R D is selected from C1-C4 alkyl groups and C2-C4 alkyl groups substituted with hydroxy groups. The surface stabilizer is

[0101]

[0100] The nanosilver platelets described herein having a surface stabilizer of general formula (V) are easily dispersible in UV-Vis radiation curable inks. Upon printing, the nanosilver platelets described herein migrate from the ink layer mass obtained with the UV-Vis radiation curable inks described herein to the ink layer-air interface and the ink layer-substrate interface and align themselves to form a thin layer of nanosilver platelets at said interfaces, which leads to the convenient appearance of a metallic yellow color observed in incident light. This property of the UV-Vis radiation curable inks described herein is particularly advantageous because on the one hand the time required for the appearance of the metallic yellow color is compatible with the high speed requirements of industrial printing of valuable documents, and on the other hand it allows the production of dichroic security features with inks containing as little as 7.5 wt-% of nanosilver platelets, which dramatically reduces the production costs, especially for dichroic security features having a large thickness of at least about 4 μm. Depending on the thickness of the security feature being fabricated and the composition of the ink, the amount of silver nanoplatelets in the UV-Vis radiation curable ink can be adjusted to rapidly develop a metallic yellow color in reflected light without affecting the blue hue and saturation in transmitted light.

[0102]

[0101] The silver nanoplatelets contained in the UV-Vis radiation curable ink can be in the form of disks, regular hexagons, triangles, especially equilateral triangles, and truncated triangles, especially truncated equilateral triangles, or mixtures thereof, preferably in the form of disks, truncated triangles, hexagons, or mixtures thereof.

[0103]

[0102] The number average diameter of the silver nanoplatelets is preferably in the range of 50-150 nm, more preferably 60-140 nm, even more preferably 70-120 nm, with a standard deviation of less than 60%, preferably less than 50%, where the number average diameter is determined by transmission electron microscopy. The diameter of a silver nanoplatelet is the longest dimension of said silver nanoplatelet and corresponds to the largest dimension of said silver nanoplatelet when oriented parallel to the plane of a transmission electron microscopy (TEM) image. As used herein, the term "number-average diameter of silver nanoplatelets" refers to the number-average diameter determined by transmission electron microscopy (TEM) using image analysis software (Thorsten Wagner ij-particlesizer v.1.0.9; DOI:10.5281 / zenodo.820296) based on measurements of at least 300, in particular at least 500 randomly selected silver nanoplatelets oriented parallel to the plane of the transmission electron microscopy image (TEM), where the diameter of the silver nanoplatelet is the largest dimension (maximum Feret diameter) of said silver nanoplatelet oriented parallel to the plane of the transmission electron microscopy image (TEM). The TEM analysis was performed using a ZEISS EM 910 instrument (INST.109) in bright field mode with an e-beam acceleration voltage of 100 kV. To perform the TEM analysis, a dispersion of silver nanoplatelets in isopropanol was used, preferably with a suitable concentration of less than 24.1 wt-%.

[0104]

[0103] The number average thickness of the silver nanoplatelets is preferably in the range of about 5 nm to about 30 nm, more preferably about 7 nm to about 25 nm, even more preferably about 8 nm to about 25 nm, with a standard deviation of less than 50%, preferably less than 30%, where the number average thickness is determined by transmission electron microscopy. The thickness of the silver nanoplatelets is the shortest dimension of the nanoplatelets and corresponds to the maximum thickness of the silver nanoplatelets. As used herein, the term "number average thickness of silver nanoplatelets" refers to a number average thickness determined by transmission electron microscopy (TEM) based on manual measurement of at least 50, particularly at least 300, randomly selected silver nanoplatelets oriented perpendicular to the plane of the TEM image, where the thickness of the silver nanoplatelets is the maximum thickness of the silver nanoplatelets. TEM analysis was performed using a ZEISS EM 910 instrument (INST.109) in bright field mode at an e-beam accelerating voltage of 100 kV. A dispersion of silver nanoplatelets in isopropanol with an appropriate concentration, preferably lower than 24.1 wt-%, was used to perform the TEM analysis. The thickness of at least 300 randomly selected silver nanoplatelets can be determined from the cross-sectional TEM images by fitting an ellipse to the particle cross-section with software (ParticleSizer). The minor axis (shortest diameter) of the fitted ellipse is considered as the particle thickness.

[0105]

[0104] The average aspect ratio (defined as the ratio of number average diameter to number average thickness) of the silver nanoplatelets is preferably greater than about 2.0, more preferably greater than about 2.2, and even more preferably greater than about 2.5.

[0106]

[0105] Preferably, the number average diameter of the silver nanoplatelets is in the range of about 50 nm to about 150 nm with a standard deviation of less than 60%, the number average thickness is in the range of about 5 nm to about 30 nm with a standard deviation of less than 50%, and the average aspect ratio is greater than about 2.0. More preferably, the number average diameter of the silver nanoplatelets is in the range of about 70 nm to about 120 nm with a standard deviation of less than 50%, the number average thickness of the silver nanoplatelets is in the range of about 8 nm to about 25 nm with a standard deviation of less than 30%, and the average aspect ratio of the silver nanoplatelets is greater than 2.5.

[0107] The silver nanoplatelets used in the UV-Vis radiation curable inks described herein are characterized by a highest wavelength absorption maximum between 560 nm and 800 nm, preferably between 580 nm and 800 nm, and most preferably between 600 nm and 800 nm. The highest wavelength absorption maximum is approximately 5 times that of silver in water. * 10 -5 The measurements were performed using a Varian Cary 50 UV-Visible spectrophotometer at a concentration of 1000 M (mol / l). The absorption maximum has a full width at half maximum (FWHM) value in the range of 50-500 nm, preferably 70-450 nm, and more preferably 80-450 nm. The molar extinction coefficient of the silver nanoplatelets measured at the highest wavelength absorption maximum is 4000 L / (cm * Mol Ag ), especially 5000 L / (cm * Mol Ag ), especially 6000L / (cm * Mol Ag ) is greater than.

[0108] The silver nanoplatelets contained by the UV-Vis radiation curable inks described herein have a surface stabilizer of the general formula (V): [ka] [In the formula, residue R A is a C2-C4 alkyl group substituted with a hydroxy group; residue R Bis selected from C1-C4 alkyl groups and C2-C4 alkyl groups substituted with hydroxy groups; Cat + is the general formula + NH2R C R D where R is the ammonium cation C is a C2-C4 alkyl group substituted with a hydroxy group; residue R D is selected from C1-C4 alkyl groups, and C2-C4 alkyl groups substituted with hydroxy groups. Without being bound by theory, it is believed that the surface stabilizers of general formula (V) help to prevent aggregation and precipitation of the silver nanoplatelets in the inks described herein, as well as promote migration of the silver nanoplatelets from the bulk of the ink layer obtained with the inks described herein to the ink layer-air interface and the ink layer-substrate interface.

[0109]

[0108] The surface stabilizer of general formula (V) may be present in an amount of about 0.5% to about 5%, preferably about 0.5% to about 4%, and more preferably about 3% by weight percent (wt-%) of the silver nanoplatelets.

[0110]

[0109] The term "C1-C4 alkyl group" as used herein means a saturated linear or branched monovalent hydrocarbon group of one to four carbon atoms (C1-C4). Examples of C1-C4 alkyl groups include methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, iso-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(CH3)CH2CH3), and 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3).

[0111]

[0110] The term "hydroxy-substituted C2-C4 alkyl group" means a linear or branched alkyl group having 2 to 4 carbon atoms substituted with a hydroxy group (-OH). The C2-C4 alkyl group may be substituted with one or two hydroxy groups.

[0112] In the general formula (V), the residue R A may be a C2-C4 alkyl group substituted with two hydroxy groups, and the residue R B can be a C1-C4 alkyl group.

[0113] In a preferred embodiment, the residue R A and R B are each independently a hydroxy group, preferably a C2-C4 alkyl group substituted with one hydroxy group. Thus, in one embodiment, the residue R A and R B are independently selected from the group consisting of -CH2CH2OH, -CH2CH(OH)CH3, -CH2CH2CH2OH, -CH(CH3)(CH2OH), -CH2CH(OH)CH2CH3, -CH2CH2CH(OH)CH3-CH2CH2CH2CH2OH, -CH(CH3)CH(OH)CH3, -CH(CH2OH)CH2CH3, -CH(CH3)CH2CH2OH, -CH2CH(CH2OH)CH3, -CH2C(CH3)(OH)CH3, -CH2CH(CH3)CH2(OH), -CH2C(OH)(CH3)2, -CH2C(CH3)(CH2OH), more preferably selected from the group consisting of -CH2CH2OH, -CH2CH(OH)CH3, and -CH2CH2CH2OH. A and R B may be the same or different.

[0114] In the general formula (V), the residue R C may be a C2-C4 alkyl group substituted with two hydroxy groups, and the residue R D can be a C1-C4 alkyl group.

[0115] In a preferred embodiment, the residue R C and R D are each independently a hydroxy group, preferably a C2-C4 alkyl group substituted with one hydroxy group. Thus, in one embodiment, the residue R C and R D are independently selected from the group consisting of -CH2CH2OH, -CH2CH(OH)CH3, -CH2CH2CH2OH, -CH(CH3)(CH2OH), -CH2CH(OH)CH2CH3, -CH2CH2CH(OH)CH3, -CH2CH2CH2CH2OH, -CH(CH3)CH(OH)CH3, -CH(CH2OH)CH2CH3, -CH(CH3)CH2CH2OH, -CH2CH(CH2OH)CH3, -CH2C(CH3)(OH)CH3, -CH2CH(CH3)CH2CH2OH, -CH2CH(CH2OH)CH3, -CH2C(CH3)(CH2OH), -CH2C(OH)(CH3)2, -CH2C(CH3)(CH2OH), more preferably selected from the group consisting of -CH2CH2OH, -CH2CH(OH)CH3, and -CH2CH2CH2OH. C and R D may be the same or different.

[0116] Preferably, in the general formula (V), the residue R A , R B , R C and R D are each independently a C2-C4 alkyl group substituted with one hydroxyl group. More preferably, in the general formula (I), the residue R A , R B , R C and R D are independently selected from the group consisting of -CH2CH2OH, -CH2CH(OH)CH3, and -CH2CH2CH2OH. Even more preferably, in the general formula (V), the residue R A , R B , R C and R D represents -CH2CH2OH.

[0117]

[0116] To prevent aggregation and precipitation of the silver nanoplatelets upon storage, the silver nanoplatelets may have an additional surface stabilizer on their surface.

[0118] In a preferred embodiment, the silver nanoplatelets have on their surface an additional surface stabilizer of general formula (VI) [ka] [In the formula, R 1 is H, C1-C 18 alkyl, phenyl, C1-C8 alkylphenyl, or CH2COOH; R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently H, C1-C8 alkyl, or phenyl; Y is O or NR 8 and; R 8 is H, or C1-C8 alkyl; k1 is an integer ranging from 1 to 500; k2 and k3 are each independently 0 or an integer ranging from 1 to 250; k4 is 0 or 1; and k5 is an integer ranging from 1 to 5. Preferably, in general formula (II), Y represents O. Also preferably, in general formula (II), k4 is 0.

[0119]

[0118] The surface stabilizer of general formula (II) preferably has an average molecular weight (Mn) of 1000 to 20000 [g / mol], more preferably 1000 to 10000 [g / mol], and most preferably 1000 to 6000 [g / mol].

[0120]

[0119] If the surface stabilizer of formula (I) contains, for example, ethylene oxide units (EO) and propylene oxide units (PO), the order of the (EO) and (PO) can be fixed (block copolymer) or not fixed (random copolymer).

[0121] Preferably, in the general formula (VI), R 1 is H or C1-C 18 is alkyl, R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently H, CH3, or C2H5, k1 is an integer ranging from 22 to 450, k2 and k3 are each independently 0 or an integer ranging from 1 to 250, k4 is 0 or 1, and k5 is an integer ranging from 1 to 5. More preferably, in the general formula (II), R 1 is H or C1-C4 alkyl, R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently H or CH3, k1 is an integer in the range of 22 to 450, k2 and k3 are each independently 0 or an integer in the range of 1 to 100, k4 is 0, and k5 is an integer in the range of 1 to 4.

[0122] The most preferred surface stabilizers of general formula (VI) have the general formula (VI-a): [ka] [In the formula, R 1 is H or a C1-C8 alkyl group, in particular H or CH3, k1 is an integer ranging from 22 to 450, particularly from 22 to 150.

[0123]

[0122] Preferred surface stabilizers of the general formula (VI) are thiol groups having an average molecular weight (M) of 2000 to 6000, such as MPEG 2000 thiol, MPEG 3000 thiol, MPEG 4000 thiol, MPEG 5000 thiol, and MPEG 6000 thiol. n ) MPEG thiol (poly(ethylene glycol) methyl ether thiol), e.g., PEG 2000 thiol, PEG 3000 thiol, PEG 4000 thiol, PEG 5000 thiol, PEG 6000 thiol, etc., having an average M of 2000 to 6000. n The thiol group is derived from PEG thiol (O-(2-mercaptoethyl)-poly(ethylene glycol)) having the formula:

[0124] The silver nanoplatelets contained in the security ink may further comprise a surface stabilizer which is a polymer, or copolymer, as described in WO200674969, which can be obtained by a process comprising the following steps: i-1) In a first step, one or more ethylenically unsaturated monomers are polymerized in the presence of at least one nitroxyl ether having the following structural elements: [ka] where X represents a group having at least one carbon atom such that a free radical X· derived from X is capable of initiating polymerization; or i-2) In the first step, at least one stable free nitroxyl radical is produced. [ka] and polymerizing one or more ethylenically unsaturated monomers in the presence of a free radical initiator; wherein at least one monomer used in step i-1) or i-2) is a C1-C6 alkyl or hydroxy C1-C6 alkyl ester of acrylic or methacrylic acid; and optionally ii) A second step which comprises modification of the polymer or copolymer prepared in i-1) or i-2) by transesterification, amidation, hydrolysis or anhydride modification or a combination thereof.

[0125] The monomer of step i-1) or i-2) is preferably a 4-vinyl-pyridine or pyridinium-ion, a 2-vinyl-pyridine or pyridinium-ion, a 1-vinyl-imidazole or imidazolinium-ion, or a compound of formula CH2=C(R a )-(C=Z)-R b wherein R a is hydrogen or methyl; R b NH2, O - (Me + ), unsubstituted C1-C 18 Alkoxy, C2-C interrupted by at least one N and / or O atom 100 Alkoxy or hydroxy substituted C1-C 18 Alkoxy, unsubstituted C1-C 18 Alkylamino, unsubstituted di(C1-C 18 Alkyl)amino, hydroxy-substituted C1-C 18 Alkylamino or hydroxy substituted di(C1-C 18 alkyl)amino, -O(CH2) y NR 15 R 16 , or -O(CH2) y N + HR 15 R 16 An - , -N(CH2) y NR 15 R 16 , or -N(CH2) y N + HR 15 R 16 An - and where An - is a monovalent anion of an organic or inorganic acid; y is an integer from 2 to 10; R 15 is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms; R 16 is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms; Me + is a monovalent metal atom or an ammonium ion; Z is oxygen or sulfur.

[0126] The second step ii) is preferably a transesterification reaction. In step ii) the alcohol is preferably of formula R c -[O-CH2-CH2-] c —OH, where R c is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl of up to 24 carbon atoms, and c is 1 to 150.

[0127]

[0126] Preferably, step i-1) or i-2) is carried out twice to obtain a block copolymer, wherein in the first or second radical polymerization step the monomer or monomer mixture contains 50% to 100% by weight of C1-C6 alkyl esters of acrylic or methacrylic acid, based on the total monomers, and in the second or first radical polymerization step, respectively, the ethylenically unsaturated monomer or monomer mixture contains at least one monomer without a first or second ester bond.

[0128]

[0127] In the first polymerization step, the monomer or monomer mixture contains 50-100% by weight of a C1-C6 alkyl ester of acrylic or methacrylic acid (first monomer) based on the total monomers, and in the second polymerization step, the ethylenically unsaturated monomer or monomer mixture contains 4-vinyl-pyridine or pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, vinyl-imidazole or imidazolinium-ion, 3-dimethylaminoethylacrylamide, 3-dimethylaminoethylmethacrylamide or the corresponding ammonium ion, 3-dimethylaminopropylacrylamide or the corresponding ammonium ion, or 3-dimethylaminopropylmethacrylamide or the corresponding ammonium ion (second monomer).

[0129] Preferably, the nitroxyl ether has the structure: [ka] has.

[0130] The surface stabilizer is preferably a copolymer obtainable by a process comprising the following steps: i-2) In the first step, the next structural element [ka] polymerizing a first monomer which is a C1-C6 alkyl or hydroxy C1-C6 alkyl ester of acrylic or methacrylic acid, and a second monomer selected from 4-vinyl-pyridine or pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, 1-vinyl-imidazole or imidazolinium-ion, 3-dimethylaminoethylacrylamide, 3-dimethylaminoethylmethacrylamide, 3-dimethylaminopropylacrylamide, and 3-dimethylaminopropylmethacrylamide, in the presence of at least one nitroxyl ether having the formula: ii) a second step comprising the modification by transesterification of the polymer or copolymer prepared in i-1), wherein the alcohol of step ii) is of formula R c -[O-CH2-CH2-] c —OH, where R c is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl of up to 24 carbon atoms, and c is 1 to 150.

[0131] Preferably, the surface stabilizer obtained by the processes described herein is a copolymer of formula (VII): [ka] [In the formula, R 17a , R 17b and R 17c are each independently H or methyl; R 18a and R 18b is H or methyl; R 19a is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms; R 19b is R c -[O-CH2-CH2-] c -O-; R 19c teeth [ka] , -C(=O)-NH-(CH2) y NR 15 R 16 or -C(=O)-NH-(CH2) y N + HR 15 R 16 An - and; where An -is a monovalent anion of an organic or inorganic acid; y is an integer from 2 to 10; R 15 is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms; R 16 is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms; R c is a saturated or unsaturated, linear or branched chain alkyl of 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl of 24 or fewer carbon atoms; c is 1 to 150; and y1, y2 and y3 are each independently an integer between 1 and 200. The order of the monomers with the subscripts y1 and y2 in general formula (VII) may be fixed (block copolymer) or may not be fixed (random copolymer).

[0132]

[0131] Surface stabilizers of general formula (VII) are described in WO200674969.

[0133] A preferred surface stabilizer of formula (VII) is a compound of formula (VII-a) [ka] [In the formula, R 18a and R 18b is H or methyl; y1, y2, and y3 are each independently an integer of 1 to 200; and c is an integer from 1 to 150. The order of the monomers with subscripts y1 and y2 may be fixed (block copolymer) or may not be fixed (random copolymer).

[0134]

[0133] Examples of preferred copolymers for use as surface stabilizers are the copolymers described in Examples A3 and A6 of WO200674969.

[0135] To improve the stability of the optical properties of the silver nanoplatelets upon storage or exposure to heat, the silver nanoplatelets may have an additional surface stabilizer of general formula (VIII): [ka] [In the formula, R 9 is a hydrogen atom or a group of the formula -CHR 11 -N(R 12 )(R 13 ) group; R 10 is a hydrogen atom, a halogen atom, a C1-C8 alkoxy group, or a C1-C8 alkyl group; R 11 is H, or C1-C8 alkyl; R 12 and R 13 are each independently a C1-C8 alkyl, a hydroxy C1-C8 alkyl group, or a group of the formula -[(CH2CH2)-O] n1 -CH2CH2-OH group, and n1 is 1 to 5.

[0136] Examples of compounds of formula (VIII) include, but are not limited to: [ka] There is.

[0137] The dispersion of silver nanoplatelets used to prepare the UV-Vis radiation curable inks described herein is obtained by using a method comprising the following steps: 1) A silver precursor, a compound of formula (VI) [ka] [In the formula, R 1 is H, C1-C 18 alkyl, phenyl, C1-C8 alkylphenyl, or CH2COOH; R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently H, C1-C8 alkyl, or phenyl; Y is O or NR 8 and; R 8 is H, or C1-C8 alkyl; k1 is an integer ranging from 1 to 500; k2 and k3 are each independently 0 or an integer ranging from 1 to 250; k4 is 0 or 1; k5 is an integer ranging from 1 to 5; A polymer or copolymer obtainable by a process comprising the steps of: i-1) In the first step, the structural element [ka] (wherein X represents a group having at least one carbon atom such that the free radical X derived from X is capable of initiating polymerization). or polymerizing one or more ethylenically unsaturated monomers in the presence of at least one nitroxyl ether having the formula: i-2) In the first step, at least one stable free nitroxyl radical is produced. [ka] and polymerizing one or more ethylenically unsaturated monomers in the presence of a free radical initiator; wherein at least one monomer used in step i-1) or i-2) is a C1-C6 alkyl or hydroxy C1-C6 alkyl ester of acrylic or methacrylic acid; and optionally ii) a second step comprising modification of the polymer or copolymer prepared in i-1) or i-2) by transesterification, amidation, hydrolysis or anhydride modification or a combination thereof; Preparing a solution containing water and, optionally, an antifoam agent; 2) preparing a solution containing a reducing agent having at least one boron atom in its molecule and water; 3) adding the solution obtained in step 1) to the solution obtained in step 2) and adding one or more complexing agents; 4) adding a solution of hydrogen peroxide in water; and 5) Adding one or more surface stabilizers to the mixture resulting from step 4).

[0138]

[0137] Silver precursors are AgNO3; AgClO4; Ag2SO4; AgCl; AgF; AgOH; Ag2O; AgBF4; AgIO3; AgPF6; R 200 CO2Ag, R 200 SO3Ag (where R 200 is unsubstituted or substituted C1-C 18 Alkyl, unsubstituted or substituted C5-C8 cycloalkyl, unsubstituted or substituted C7-C 18 Aralkyl, unsubstituted or substituted C6-C 18 Aryl or unsubstituted or substituted C2-C 18 heteroaryl); a silver(I) compound selected from the group consisting of dicarboxylic acids, tricarboxylic acids, polycarboxylic acids, polysulfonic acids, Ag salts of P-containing acids, and mixtures thereof, preferably silver nitrate, silver acetate, silver perchlorate, silver methanesulfonate, silver benzenesulfonate, silver toluenesulfonate, silver trifluoromethanesulfonate, silver sulfate, silver fluoride, and mixtures thereof, more preferably silver nitrate.

[0139] The reducing agent is selected from the group consisting of alkali or alkaline earth metal borohydrides such as sodium borohydride, alkali or alkaline earth metal acyloxyborohydrides such as sodium triacetoxyborohydride, alkali or alkaline earth metal alkoxy or aryloxyborohydrides such as sodium trimethoxyborohydride, aryloxyboranes such as catecholborane, and amine-borane complexes such as diethylaniline borane, tert-butylamine borane, morpholine borane, dimethylamine borane, triethylamine borane, pyridine borane, ammonia borane, and mixtures thereof. Sodium borohydride is most preferred.

[0140]

[0139] The one or more complexing agents are selected from the group of chlorine-containing compounds capable of liberating chloride ions under reaction conditions, such as metal chlorides, alkyl or aryl ammonium chlorides, phosphonium chlorides; primary or secondary amines and the corresponding ammonium salts, such as methylamine or dimethylamine; ammonia and the corresponding ammonium salts; and aminocarboxylic acids and their salts, such as ethylenediaminetetraacetic acid.

[0141]

[0140] Non-limiting examples of complexing agents include ammonia, methylamine, dimethylamine, ethylamine, ethylenediamine, diethylenetriamine, ethylenediamine-tetraacetic acid (EDTA); ethylenediamine N,N'-disuccinic acid (EDDS); methylglycine diacetic acid (MGDA); diethylenetriaminepentaacetic acid (DTPA); propylenediaminetetraacetic acid (PDTA); glutamic acid N,N-diacetic acid (N,N-dicarboxymethylglutamic acid tetrasodium salt (GLDA); nitrilotriacetic acid (NTA), and any salts thereof; N-hydroxyethylethylenediaminetriacetic acid (HEDTA), triethylenetetraaminehexaacetic acid (TTHA), N-hydroxyethyliminodiacetic acid (HEIDA), dihydroxyethylglycine (DHEG), ethylenediaminetetrapropionic acid (EDTP) and derivatives thereof, such as the trisodium salt of methylglycine diacetic acid (Na3MGDA) and the tetrasodium salt of EDTA.

[0142]

[0141] The antifoaming agent is a compound or composition capable of suppressing the formation of foam in the reaction mixture, such as, for example, commercially available TEGO® Foamex 1488, 1495, 3062, 7447, 800, 8030, 805, 8050, 810, 815N, 822, 825, 830, 835, 840, 842, 843, 845, 855, 860, 883, K3, K7, K8, N, Sigma's Antifoam SE-15, Struktol SB-2080, etc. The amount of antifoaming agent ranges from 0.00001% to 5% by weight, preferably from 0.0001% to 3%, more preferably from 0.001% to 2% by weight, based on the total weight of the reaction mixture before the addition of hydrogen peroxide.

[0143]

[0142] An antifoaming agent can be added to the solution prepared in step 1) and / or to the solution prepared in step 2).

[0144]

[0143] The silver nanoplatelet formation reaction is carried out by gradually adding the silver precursor solution to the reducing agent solution, while the temperatures of both solutions are in the range of -3°C to 40°C, and the gradual addition is completed within 15 min to 24 h.

[0145]

[0144] The silver nanoplatelets obtained in step 4) and / or 5) can be subjected to further purification and / or isolation methods such as decantation, (ultra)filtration, (ultra)centrifugation, reversible or irreversible flocculation, phase transfer with organic solvents, and combinations thereof. The dispersion of silver nanoplatelets can contain up to about 99 wt-% silver nanoplatelets, preferably 5 wt-% to 99 wt-% silver nanoplatelets, more preferably 5 wt-% to 90 wt-% silver nanoplatelets, where wt-% is based on the total weight of the dispersion.

[0146] Starting from the silver nanoplatelets obtained by purification and / or isolation, the silver nanoplatelets having a surface stabilizer of general formula (V) can be prepared: i) CS2 in the presence of silver nanoplatelets is reacted with A R BNH reacts with an amine and then R C R D Treatment with NH or ii) CS2 is dissolved in water in the following manner. A R B Reacting NH with an amine and then R C R D Treatment with NH gives the dithiocarbamate of general formula (I), which is then reacted with silver nanoplatelets. It can be prepared by the following.

[0147]

[0146] R A R C is the same as R B R D The silver nanoplatelets having a dithiocarbamate of general formula (V) which is the same as iii) CS2 in the presence of silver nanoplatelets is reacted with CS2 according to the formula R A R B by reacting with amines of NH; or iv) CS2 is dissolved in water in the following manner. A R B NH reacts with amines of the general formula

[0148]

[0147] [ka] This is then reacted with silver nanoplatelets. This can be obtained by:

[0149]

[0148] The silver nanoplatelets described in this specification are disclosed in European Patent Application No. 20206698.1, entitled "Composition Comprising Silver Nanoplatelets," filed on November 10, 2020 by BASF SE.

[0150] According to one embodiment, the UV-Vis radiation curable ink is a cationically curable composition comprising silver nanoplatelets as described herein; one or more cycloaliphatic epoxides as described herein (preferably according to formula (I) or (II) as described herein); one or more cationic photoinitiators as described herein (preferably selected from the group consisting of iodonium salts, sulfonium salts and mixtures thereof as described herein); one or more vinyl ethers, one or more oxetanes as described herein or epoxides other than cycloaliphatic epoxides as described herein; a perfluoropolyether surfactant as described herein (preferably a perfluoropolyether surfactant functionalized with one or more hydroxyl functional groups as described herein); a polyvinyl chloride copolymer as described herein, optionally one or more photosensitizers as described herein (preferably a thioxanthone as described herein); and optionally one or more organic solvents as described herein, preferably in the amounts as described herein. According to one embodiment, the UV-Vis radiation curable ink is a cationically curable composition comprising: silver nanoplatelets as described herein; one or more cycloaliphatic epoxides as described herein (preferably according to formula (I) or (II) as described herein); one or more cationic photoinitiators as described herein (preferably selected from the group consisting of iodonium salts, sulfonium salts and mixtures thereof as described herein); a perfluoropolyether surfactant as described herein (preferably a perfluoropolyether surfactant functionalized with one or more hydroxyl functional groups as described herein); a polyvinyl chloride copolymer as described herein, optionally one or more photosensitizers as described herein (preferably a thioxanthone as described herein); and one or more organic solvents as described herein, preferably in the amounts described herein.

[0151]

[0150] According to one embodiment, the UV-Vis radiation curable ink comprises silver nanoplatelets as described herein; one or more cycloaliphatic epoxides as described herein (preferably according to formula (I) or (II) as described herein); one or more cationic photoinitiators as described herein (preferably selected from the group consisting of iodonium salts, sulfonium salts and mixtures thereof as described herein); one or more vinyl ethers, one or more oxetanes as described herein or epoxides other than cycloaliphatic epoxides as described herein; one or more radically curable compounds as described herein (particularly acrylate oligomers and acrylates as described herein); A hybrid curable composition comprising an acrylate monomer, preferably a (meth)acrylate as described herein), one or more free radical photoinitiators as described herein (a phosphine oxide as described herein); a perfluoropolyether surfactant as described herein (preferably a perfluoropolyether surfactant functionalized with one or more hydroxyl functional groups as described herein); a polyvinyl chloride copolymer as described herein; optionally one or more photosensitizers as described herein (preferably anthracene as described herein); and optionally one or more organic solvents as described herein, preferably in the amounts described herein.According to one embodiment, the UV-Vis radiation curable ink is a hybrid curable composition comprising: silver nanoplatelets as described herein; one or more cycloaliphatic epoxides as described herein (preferably according to formula (I) or (II) as described herein); one or more cationic photoinitiators as described herein (preferably selected from the group consisting of iodonium salts, sulfonium salts and mixtures thereof as described herein); one or more radically curable compounds as described herein (particularly acrylate oligomers and acrylate monomers as described herein, preferably (meth)acrylates as described herein), one or more free radical photoinitiators as described herein (phosphine oxides as described herein); perfluoropolyether surfactants as described herein (preferably perfluoropolyether surfactants functionalized with one or more hydroxyl functional groups as described herein); a polyvinyl chloride copolymer as described herein; optionally one or more photosensitizers as described herein (preferably anthracene as described herein); and one or more organic solvents as described herein, preferably in the amounts described herein.

[0152] The method described herein further comprises, after step a) as described herein, step b) of at least partially applying a top-coating composition as described herein onto the coating layer (x10) as described herein, the top-coating composition as described herein being applied in the form of one or more indicia (x30) as described herein, overlapping (i.e. overlapping in at least one area) the coating layer (x10) as described herein, wherein the UV-Vis radiation curable ink contained in the coating layer (x10) is still in a wet, unpolymerized state.

[0153]

[0152] As used herein, the term "indicium" / "indicia" refers to a continuous and / or discontinuous layer / layers of a distinctive mark / s or sign / s or pattern / s. Preferably, the indicium / s described herein is / are selected from the group consisting of codes, symbols, alphanumeric symbols, motifs, geometric patterns (e.g. circles, triangles and regular or irregular polygons), letters, words, names, numbers, logos, figures, portraits and combinations thereof. Examples of codes include coded marks, such as coded alphanumeric data, one-dimensional bar codes, two-dimensional bar codes, QR codes, data matrices and IR readable codes. The indicium / s described herein can be solid indicia and / or raster indicia.

[0154]

[0153] The topcoating composition described herein is applied in the form of one or more indicia (x30) as described herein by an application process, preferably a non-contact fluid microdispensing process, more preferably a process selected from the group consisting of spray coating, aerosol jet printing, electrohydrodynamic printing, slot-die coating and inkjet printing, even more preferably an inkjet printing process, wherein said non-contact fluid microdispensing printing process is a variable information printing method that allows for the unique creation of one or more indicia (x30) on or in the security features described herein. The application process is chosen depending on the design and resolution of the one or more indicia to be created.

[0155] The topcoating composition described herein is about 0.8 g / m 2 More than 1.0 g / m 2 and the ink deposit is measured as described later in the experimental section in paragraphs

[0209] and

[0210] .

[0156]

[0155] Spray coating is a technique that involves forming a fine aerosol by passing a composition through a nozzle. A carrier gas and electrostatic charge may be included to help direct the aerosol onto the surface to be printed. Spray printing makes it possible to print dots and lines. Compositions suitable for spray printing typically have a viscosity of about 10 mPa.s to about 1 Pa.s (25°C, 1000 s -1 , as mentioned above). The resolution of spray coating printing is in the millimeter range. Spray printing is described for example in F.C. Krebs, Solar Energy Materials & Solar Cells (2009), 93, page 407.

[0157] Aerosol jet printing (AJP) is a new non-contact direct-write technique aimed at producing fine features on a wide range of substrates. AJP is compatible with a wide range of materials and freeform deposition, allowing high resolution (on the order of about 10 micrometers) coupled with relatively large standoff spacing (e.g., 1-5 mm) as well as orientation independence. The technique is typically applied at a flow rate of about 1 mPa.s to about 1 Pa.s (25° C., 1000 s -1 Aerosol generation includes using ultrasonic or pneumatic atomizers to generate an aerosol from a composition having a viscosity of 1000 .mu.m (as described above). Aerosol jet printing is described, for example, in N.J. Wilkinson et al., The International Journal of Advanced Manufacturing Technology (2019) 105:4599-4619.

[0158] Electrohydrodynamic inkjet printing is a high resolution inkjet printing technique. Electrohydrodynamic inkjet printing uses an externally applied electric field to manipulate droplet size, ejection frequency and placement on a substrate to obtain higher resolution than conventional inkjet printing while maintaining high production rates. The resolution of electrohydrodynamic inkjet printing is about two orders of magnitude higher than conventional inkjet printing; therefore, it can be used to direct nano- and microscale patterns. Electrohydrodynamic inkjet printing can be used in both DOD or continuous modes. Compositions for electrohydrodynamic inkjet printing typically have a viscosity of 1 mPa.s to about 1 Pa.s (at 25° C., 1000 s). -1 , supra). Electrohydrodynamic inkjet printing techniques are described for example in PV Raje and NC Murmu, International Journal of Emerging Technology and Advanced Engineering, (2014), 4(5), pages 174-183.

[0159]

[0158] Slot die coating is a one-dimensional coating technique. Slot die coating allows for the coating of stripes of material well suited for producing multi-layer coatings with stripes of different materials layered on top of each other. The pattern alignment is produced by a coating head moving along a direction perpendicular to the direction of web movement. A slot die coating head includes a mask that defines a slot in the coating head through which the slot die coating ink is dispersed. An example of a slot die coating head is shown in F.C.K.rebs, Solar Energy Materials & Solar Cells (2009), 93, pages 405-406. Compositions suitable for slot die coating typically have a viscosity of 1 mPa.s to about 20 mPa.s (at 25°C, 1000 s -1 , as above).

[0160] According to one embodiment, the top coating composition described herein is printed in the form of one or more indicia (x30) as described herein by an inkjet printing process, preferably a continuous inkjet (CI) printing process or a drop-on-demand (DOD) inkjet printing process, more preferably a drop-on-demand (DOD) inkjet printing process. Drop-on-demand (DOD) printing is a non-contact printing process, where droplets are only generated when needed for printing, generally by an ejection mechanism rather than destabilizing a jet. Depending on the mechanism used in the printhead to create the droplets, DOD printing can be performed by piezo impulse, thermal jet, valve jet (viscosity 1 mPa.s to about 50 mPa.s (at 25°C, 1000 s -1 , as above) and electrostatic processes.

[0161] According to a preferred embodiment, the topcoating compositions described herein are measured at 25° C. and 1000 s using a rotational viscometer DHR-2 (TA Instruments) having a cone-plane geometry and a diameter of 40 mm. -1 and preferably has a viscosity of less than about 40 mPa.s, more preferably from about 0.5 mPa.s to about 30 mPa.s, and even more preferably from about 0.5 mPa.s to about 20 mPa.s.

[0162]

[0161] In accordance with one embodiment for the UV-Vis radiation cationically curable inks described herein, the top coating compositions described herein may comprise a blend of one or more cationically curable compounds, one or more hybrid curable compounds, one or more solvents, one or more radically curable compounds and one or more radical photoinitiators or mixtures thereof; wherein the one or more cationically curable compounds may be as described herein for the UV-Vis radiation curable inks described herein, preferably selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, glycidyl ethers, oxetanes, and tetrahydrofuran, and mixtures thereof, such as those described herein, more preferably selected from the group consisting of vinyl ethers, cyclic ethers such as epoxides, glycidyl ethers, oxetanes, and mixtures thereof, such as those described herein, more preferably selected from the group consisting of vinyl ethers, glycidyl ethers, oxetanes, and mixtures thereof, such as those described herein; Here, glycidyl ethers include monoglycidyl ethers (e.g., alkyl (e.g., methyl, ethyl, propyl, isopropyl, butyl, tert butyl, 2-ethylhexyl, and C8-C18 (used alone or as a mixture thereof)) monoglycidyl ethers, cycloalkyl (e.g., cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl) monoglycidyl ethers, alkenyl (e.g., allyl and crotyl) monoglycidyl ethers, alkynyl (e.g., propargyl) monoglycidyl ethers, phenyl (e.g., phenyl, cresyl, tert butylphenyl, and nonylphenyl) monoglycidyl ethers, and furfuryl monoglycidyl ether), diglycidyl ethers (e.g., diglycidyl ether, 1,2-propanediol diglycidyl ether, 1,3-propanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, ethers, 4,4'-dihydroxyphenyl-2,2-propane diglycidyl ether, resorcinol diglycidyl ether, bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether and polyglycol diglycidyl ethers, triglycidyl ethers (including, for example, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, triphenylolmethane triglycidyl ether, ether castor oil triglycidyl ether, propoxylated glycerin triglycidyl ether), tetraglycidyl ethers (including, for example, pentaerythritol tetraglycidyl ether and 1,1,2,2-tetrakis(hydroxyphenyl)ethane tetraglycidyl ether), polyglycidyl ethers (including, for example, sorbitol polyglycidyl ether and polyphenol polyglycidyl ether) and mixtures thereof; If the one or more glycidyl ethers have a viscosity that is not suitable for inkjet printing, the top coating compositions described herein comprise said one or more glycidyl ethers in combination with one or more monoglycidyl ethers and / or one or more diglycidyl ethers and / or one or more solvents to reduce the viscosity; One or more hybrid curing compounds are hydroxy-modified or (meth)acrylate-modified vinyl ethers, in particular VEEA from Nippon Shokubai, 2-(2-vinyloxyethoxy)ethyl acrylate and methyl 2-((allyloxy)methyl)acrylate (AOMA™) from Nippon Shokubai; the one or more solvents are selected from the group consisting of alcohols (especially ethanol), ketones (especially cyclic ketones, such as cyclopentanone and cyclohexanone), glycols, glycol ethers (especially dipropylene glycol methyl ether), ether esters (especially ethyl 3-ethoxypropionate), glycol ether esters (especially propylene glycol methyl ether acetate), alkylene carbonates (especially propylene carbonate) and mixtures thereof; The one or more radically curable compounds are selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, such as those described herein, tetra(meth)acrylates, such as those described herein, and mixtures thereof, and one or more free radical photoinitiators, such as those described herein (particularly alpha-hydroxyketones, such as those described herein); suitable mono(meth)acrylates include alkyl(meth)acrylates, cycloalkyl(meth)acrylates (such as 3,3,5-trimethylcyclohexyl acrylate and isobornyl acrylate), benzyl(meth)acrylate, phenyl(meth)acrylate (including phenoxyalkyl(meth)acrylates, such as phenoxyethyl acrylate), cyclic trimethylolpropane formal acrylate, tetrahydrofurfuryl acrylate, aliphatic acrylates, and the like. Suitable di(meth)acrylates are selected from the group consisting of ethylene glycol diacrylate, glycol dimethacrylate, butanediol di(meth)acrylate, 2-methyl-1,3-propanediol diacrylate, 3-methyl-1,5-pentanediol diacrylate, 2-butyl-2-ethyl-1,3-propanediol diacrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, alkoxylated (especially ethoxylated and propoxylated) 1,6-hexanediol diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated 2-methyl-1,3-propanediol diacrylate, tricyclodecane dimethanol diacrylate, diethylene glycol di(meth)acrylate, dipropylene glycol diacrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate and polyethylene glycol 200 / 400 / 600 di(meth)acrylate, more preferably the free radical photoinitiator is selected from the group consisting of hydroxyketones (e.g. alpha-hydroxyketones), benzil ketals, benzoin ethers, phosphine oxides, phenyl glyoxylates and mixtures thereof, more preferably the group consisting of phosphine oxides, hydroxyketones, phenyl glyoxylates and mixtures thereof, even more preferably the group consisting of hydroxyketones (e.g. alpha-hydroxyketones).

[0163]

[0162] Optionally, to improve the curing efficiency of the UV-Vis radiation cationically curable inks described herein, the top coating compositions described herein may further comprise one or more cationic photoinitiators.

[0164]

[0163] In accordance with one embodiment for the UV-Vis radiation hybrid curable inks described herein, the top coating compositions described herein may comprise one or more cationically curable compounds, one or more hybrid curable compounds, one or more solvents, one or more radically curable compounds or mixtures thereof; wherein the one or more cationically curable compounds may be those described herein for the UV-Vis radiation curable inks described herein, preferably selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, glycidyl ethers, oxetanes, and tetrahydrofurans, and mixtures thereof, such as those described herein, more preferably selected from the group consisting of vinyl ethers, glycidyl ethers, oxetanes, and mixtures thereof, such as those described herein; One or more hybrid curing compounds are hydroxy-modified or (meth)acrylate-modified vinyl ethers, in particular VEEA from Nippon Shokubai, 2-(2-vinyloxyethoxy)ethyl acrylate and methyl 2-((allyloxy)methyl)acrylate (AOMA™) from Nippon Shokubai; the one or more solvents are selected from the group consisting of alcohols (especially ethanol), ketones (especially cyclic ketones, such as cyclopentanone and cyclohexanone), glycols, glycol ethers (especially dipropylene glycol methyl ether), ether esters (especially ethyl 3-ethoxypropionate), glycol ether esters (especially propylene glycol methyl ether acetate), alkylene carbonates (especially propylene carbonate) and mixtures thereof; The one or more radically curable compounds are selected from the group consisting of mono(meth)acrylates, such as those described herein, di(meth)acrylates, such as those described herein, tri(meth)acrylates, such as those described herein, tetra(meth)acrylates, such as those described herein, and mixtures thereof.

[0165]

[0164] Optionally, to improve the curing efficiency of the UV-Vis radiation hybrid curable inks described herein, the top coating compositions described herein may further comprise one or more cationic photoinitiators and / or one or more free radical photoinitiators, such as those described herein.

[0166]

[0165] In embodiments where the top coating composition is applied by an ink jet printing process, said top coating composition may further comprise conventional additives and components used in the radiation curable ink jet field, such as, for example, reactive diluents, wetting agents, defoamers, surfactants and mixtures thereof.

[0167]

[0166] The method described herein further comprises, after step b), a step c) of curing the coating layers (x10) and the one or more indicia (x30) described herein with one or more curing units (x50) described herein. Preferably, the curing step c) described herein is performed with one or more curing units (x50) (also referred to in the art as light sources) selected from the group consisting of mercury lamps (preferably medium pressure mercury lamps), UV-LED lamps and sequences thereof. A typical sequence includes the use of one or more UV-LED lamps in a first step to at least partially cure the UV-Vis radiation ink and the one or more indicia (x30) and one or more medium pressure mercury lamps in a second step. Mercury lamps are advantageous since they emit light in a wide range of wavelengths in the UV-A, UV-B and UV-C ranges. Thus, there is a wide choice of photoinitiators or photoinitiator / photosensitizer combinations having an absorption spectrum that matches at least one of the emission bands of the mercury lamps. UV-LEDs have a more limited wavelength range, so only a limited selection of photoinitiators or photoinitiator / photosensitizer combinations are efficient enough at industrial printing speeds. On the other hand, UV-LEDs are less costly, require less energy (especially requiring much less heat dissipation systems), are less susceptible to ozone formation, and have a much longer lifespan.

[0168]

[0167] The time between step b) described herein and step c) described herein is less than 5 seconds, preferably less than about 4 seconds, and more preferably equal to or less than about 3.5 seconds.

[0169]

[0168] The present invention provides a method as described herein for producing a security feature exhibiting one or more indicia (x30) on a substrate (x20) as described herein and a substrate (x20) comprising one or more security features resulting therefrom and a security feature produced by the method as described herein exhibiting one or more indicia (x30) as described herein. The shape of the security feature as described herein may be continuous or discontinuous. According to one embodiment, the shape of the coating layer (x10) represents one or more indicia, dots and / or lines, wherein said indicia may have the same shape as the one or more indicia (x30) made of the top-coating composition as described herein or may have a different shape.

[0170]

[0169] Preferably, the UV-Vis radiation curable inks described herein are applied to a transparent or partially transparent area of ​​a substrate by the methods described herein. As used herein, "transparent or partially transparent area of ​​a substrate" refers to an area of ​​a substrate, wherein said area is characterized by an average transmittance in the visible range of at least 50%, preferably at least 70%, more preferably at least 90%. The transparent or partially transparent area of ​​a substrate and the remaining area of ​​the substrate can be made of the same material or different materials. Removal of one or more layers in a multi-layer structure, or application of a transparent or partially transparent material to an aperture in a substrate made of a different material from the transparent or partially transparent material, provides a value document substrate in which the transparent or partially transparent area of ​​the substrate and the remaining area of ​​the substrate are made of different materials.

[0171]

[0170] Materials for the value document or value article substrate include, without limitation, 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, without limitation, hemp, cotton, linen, wood pulp, and blends thereof. As is known to those skilled in the art, cotton and cotton / linen blends are preferred for banknotes, while wood pulp is typically used for non-banknote security documents. Typical examples of plastics and polymers include polystyrene, polycarbonate, polyolefins such as polyethylene (PE) and polypropylene (PP), such as biaxially oriented polypropylene (BOPP), polyamide (PA), polyesters such as poly(ethylene terephthalate) (PET), polyethylene terephthalate glycol-modified (PETG), such as poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate), poly(1,4-butylene terephthalate) (PBT), and poly(ethylene 2,6-naphthoate) (PEN), and polyvinyl chloride (PVC). Typical examples of composites include, without limitation, multilayer structures or laminates of paper and at least one plastic or polymeric material, such as those listed above. Suitable materials for the transparent or partially transparent regions of the substrate include, but are not limited to, polystyrene, polycarbonate, polyolefins such as polyethylene (PE) and polypropylene (PP), such as biaxially oriented polypropylene (BOPP), polyamide (PA), polyesters such as poly(ethylene terephthalate) (PET), polyethylene terephthalate glycol-modified (PETG), such as poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate), poly(1,4-butylene terephthalate) (PBT), and poly(ethylene 2,6-naphthoate) (PEN), and polyvinyl chloride (PVC). The transparent or partially transparent regions of the substrate of the value document may have a primer layer onto which a UV-Vis radiation curable ink is printed.The primer layer can be obtained by UV-Vis curing a varnish containing all the components of the UV-Vis radiation curable ink described herein except for the silver nanoplatelets.

[0172]

[0171] Also described herein is a method for producing a document of value, an item of value or a decorative element or object, the method comprising the steps of: a) preparing a document of value, an item of value or a decorative element or object; and b) providing one or more of the security features described herein, in particular those obtained by the methods described herein, so that they are included by the document of value, the item of value or the decorative element or object.

[0173]

[0172] The present invention further provides value documents and value articles comprising a security feature as described herein or one or more of the security features as described herein.The present invention further provides value documents and value articles comprising a substrate as described herein and a security feature as described herein or one or more of the security features as described herein.

[0174]

[0173] Preferably, the value document is selected from banknotes, certificates, tickets, cheques, receipts, revenue stamps, contracts, identity documents, such as passports, identity cards, visas, driver's licenses, bank cards, credit cards, transaction cards, access documents, and cards, admission tickets, public transport tickets, academic diplomas, and academic titles. More preferably, the value document is a banknote. The UV-Vis radiation curable inks described herein may also be used to create security features directly on value items, including value goods. The term "value goods" relates to packaging materials that can be protected against counterfeiting and / or illegal copying, for example to ensure the contents of the package, such as genuine medicines, especially in the pharmaceutical, cosmetic, electronics or food industries. Alternatively, the security features described herein may be created on auxiliary substrates, such as security threads, security stripes, foils, decals, windows or labels, and then transferred to the value document or value item in a separate step.

[0175]

[0174] To further increase the security level of value documents and items of value and their resistance to counterfeiting and illegal duplication, the substrates described herein may contain printed, coated, or laser engraved or laser drilled indicia, watermarks, security threads, fibers, planchets, luminescent compounds, windows, foils, decals, primers and combinations of two or more thereof.

[0176]

[0175] One or more protective layers may be applied onto the security features or value documents or value articles described herein in order to increase the durability and cleanliness by stain or chemical resistance and thus the circulation life of the value documents and value articles, or to modify their aesthetic appearance (e.g. optical gloss). When present, the one or more protective layers are typically made of a protective varnish which may be transparent or more or less pigmented or tinted and more or less glossy. The protective varnish may be a radiation curable composition, a heat drying composition or any combination of these. Preferably, the one or more protective layers are made of a radiation curable, more preferably a UV-Vis radiation curable, composition. Compositions suitable as one or more protective layers are described in WO 2020 / 234211, WO 2013 / 127715 and WO 2014 / 067715.

[0177]

[0176] The security feature showing one or more indicia (x30) as described herein may be applied directly onto the substrate and remain permanently on this substrate (as in banknote applications). Alternatively, the security feature may also be applied onto a temporary substrate for production purposes, from which the security feature is subsequently removed. Then, after hardening / curing the UV-Vis radiation curable inks described herein for the production of the security feature, the temporary substrate may be removed from the security feature.

[0178]

[0177] Alternatively, in another embodiment, an adhesive layer may be present on the security feature or on the substrate comprising said security feature, said adhesive layer being on the surface of the substrate opposite to the surface on which the security feature is provided or on the same side as the security feature. Thus, an adhesive layer may be applied to the security feature or to the substrate, said adhesive layer being applied after the curing step is completed. Such an article may be applied to any kind of document or other article or item without printing or other machines and processes requiring a somewhat high effort. Alternatively, the substrate described herein comprising the security features described herein may be in the form of a transfer foil, which can be applied to the document or article in a separate transfer step. For this purpose, the substrate is provided with a release coating and the security feature is prepared thereon as described herein. One or more adhesive layers may be applied over the security feature so prepared.

[0179]

[0178] Also described herein are substrates, value documents, items of value, including commodities, decorative elements and objects that include more than one security feature as described herein, i.e., two, three, four, etc. Also described herein are articles, particularly value documents, items of value, including commodities, decorative elements or objects that include the security features as described herein.

[0180]

[0179] As noted above, the security features described herein may be used to protect and authenticate items of value, including value documents and value commodities.

[0181]

[0180] Those skilled in the art may foresee some modifications to the specific embodiments described above without departing from the spirit of the present invention. Such modifications are encompassed by the present invention.

[0182]

[0181] Additionally, all documents referenced throughout this specification are incorporated herein by reference as if fully set forth herein in their entirety. EXAMPLES

[0183]

[0182] The invention will now be described in more detail with reference to the following non-limiting examples, which provide more details regarding the preparation of a security feature obtained by applying a top-coating inkjet ink (IJ1-IJ14) in the form of one or more indicia (x30) to a coating layer (x10) made of a UV-Vis radiation cationic or hybrid curable screen ink containing silver nanoplatelets (SP1-SP10) and curing said one or more indicia (x30) and said coating layer (x10) in a curing unit (x50).

[0184]

[0183] Tables 1A and 1B provide a description of the UV-Vis radiation cationic or hybrid curable screen printing inks that were used.

[0185]

[0184] Tables 2A and 2B provide a description of top-coating inkjet inks (IJ1 to IJ14) that are applied in the form of one or more indicia (x30) to a coating layer (x10) made of screen-printed ink.

[0186] Table 3A-H provides the optical properties of security features obtained by the method of the invention (Examples E1-E48) and the comparative method (C1-C8), where the top-coated inkjet inks were applied with different ink coverage values ​​(g / m 2 ) was applied.

[0187]

[0186] Tables 4A-B provide the optical properties of security features obtained by the method of the present invention (Examples E49-E68), where the composition of the UV-Vis radiation cationic or hybrid curable screen printing ink was varied.

[0188]

[0187] Tables 5A-B provide the optical properties of security features obtained by the method of the present invention (Examples E69-E83), where the composition of the top-coating inkjet ink was varied.

[0189]

[0188] Tables 6A-B provide the optical properties of security features obtained by the method of the invention (Examples E84-E91) and comparative methods (C9-C28), in which the time between the partial application of a top-coating inkjet ink in the form of one or more indicia (x30) onto a coating layer (x10) and the curing of said one or more indicia (x30) and said coating layer (x10) was varied.

[0190] Analysis method A-1.UV-Vis spectroscopy

[0189] UV-Vis spectra of the dispersions were recorded on a Varian Cary 50 UV-visible spectrophotometer with the dispersions concentrated to achieve an optical density of 0.3-1.5 at a light path of 1 cm.

[0191] A-2.TEM analysis TEM analysis was performed on dispersions containing silver nanoplatelets in isopropanol using a ZEISS, INST.109 EM 910 instrument in bright field mode, e-beam acceleration voltage 100 kV. At least two representative images were recorded at different magnification scales (5,000x, 10,000X, 20,000X) to characterize the predominant particle morphology of each sample. The number-average diameter of the particles was determined from the TEM images using image analysis software (Thorsten Wagner ij-particlesizer v.1.0.9; DOI:10.5281 / zenodo.820296) as the largest dimension of the nanoplatelets oriented parallel to the plane of the image, based on measurements of at least 500 randomly selected particles. The number-average thickness of the particles was measured manually from the TEM images as the largest dimension of the nanoplatelets oriented perpendicular to the plane of the image, based on measurements of at least 300 randomly selected particles.

[0192]

[0191] In particular, a portion of the dispersion was transferred to a smooth foil. After drying, the samples were embedded in Araldit®, which was cross-linked at less than 60°C. Ultrathin cross-sections of the embedded samples were prepared perpendicular to the foil surface. The thickness of at least 300 randomly selected silver nanoplatelets was determined from cross-sectional TEM images (recorded at a magnification of 25.000X) by fitting an ellipse to the particle cross-section with the software (ParticleSizer). The minor axis (shortest diameter) of the fitted ellipse was taken as the particle thickness.

[0193] Preparation and characterization of silver nanoplatelet dispersions D1 and D2 B-1. Synthesis of raw materials In a 1 L double-walled glass reactor equipped with an anchor stirrer, 365 g of deionized water was cooled to +2° C. 13.62 g of sodium borohydride was added and the mixture was cooled to −1° C. while stirring at 250 revolutions per minute (RPM, solution A).

[0194] In a 0.5 L double-walled glass reactor equipped with an anchor stirrer, 132 g of deionized water and 4.8 g of MPEG-5000-thiol were combined and the mixture was stirred for 10 minutes at room temperature. 72 g of the product of Example A3 of WO2006074969 was added and the resulting mixture was stirred for an additional 10 minutes at room temperature for homogenization. A solution of 30.6 g of silver nitrate in 30 g of deionized water was added in one portion and the mixture was stirred for 10 minutes to obtain an orange-brown viscous solution. To this solution was added 96 g of deionized water, followed by 3 g of Struktol SB 2080 defoamer, previously dispersed in 36 g of deionized water. The resulting mixture was cooled to 0° C. with stirring at 250 RPM (Solution B).

[0195]

[0194] Solution B was then added subsurface to solution A via a chilled (0°C) addition tube using a peristaltic pump at a constant rate over a period of 2 h to obtain a dispersion of spherical silver nanoplatelets. Solution A was stirred at 250 RPM during pumping.

[0196] After the addition was complete, the reaction mixture was warmed to +5° C. within 15 min and a solution of 862 mg KCl in 10 g deionized water was added in one portion, followed by the addition of 9.6 g ethylenediaminetetraacetic acid (EDTA) in four equal portions at time intervals of 10 min.

[0197] After addition of the last portion of EDTA, the reaction mixture was stirred for 15 min at +5° C., then warmed to 35° C. over 30 min and stirred at this temperature for 1 h, at which point hydrogen evolution was complete.

[0198] 3.0 mL of a 30% w / w solution of ammonia in water was added, followed by 5.76 g of solid NaOH, and the mixture was stirred for 15 min at 35° C. Then 180 mL of 50% w / w aqueous hydrogen peroxide was added subsurface to the reaction mixture at a constant rate of 4 h with a peristaltic pump, stirring at 250 RPM, while maintaining the temperature at 35° C. This resulted in a deep blue dispersion of silver nanoplatelets, which was cooled to room temperature. 1.23 g of formula [ka] (a mixture of CAS 80584-88-9 and 80584-89-0) was added and the mixture was stirred for 1 h at room temperature.

[0199] B-2. Isolation and purification of Ag nanoplatelets B-2a. First Decantation

[0198] 9.6 g of sodium dodecyl sulfate was added to the reaction mixture, followed by about 25 g of anhydrous sodium sulfate powder, which was added in small portions with stirring until the color of the dispersion in transmitted light changed from blue to pink. The mixture was then kept at room temperature without stirring for 24 h, allowing the solidified nanoplatelets to settle at the bottom of the reactor.

[0200]

[0199] 890 g of the supernatant was peristaltically pumped out of the reactor, and 890 g of deionized water was added to the reactor. The mixture in the reactor was stirred at room temperature for 1 h to redisperse the coagulated particles.

[0201] B-2b. Second Decantation Approximately 64 g of anhydrous sodium sulfate powder was added in small portions with stirring until the color of the dispersion in transmitted light changed from blue to yellowish pink. The mixture was then kept at room temperature without stirring for 12 h to allow the coagulated nanoplatelets to settle to the bottom of the reactor. 990 g of the supernatant was pumped out of the reactor with a peristaltic pump, and 90 g of deionized water was added to the reactor. The resulting mixture was stirred at room temperature for 30 min to redisperse the coagulated particles.

[0202] B-2c. Submerged ultrafiltration The resulting dispersion of Ag nanoplatelets was subjected to ultrafiltration using a Millipore Amicon 8400 stirred ultrafiltration cell. The dispersion was diluted with deionized water and ultrafiltered to a final volume of about 50 mL using a polyethersulfone (PES) membrane with a 300 kDa cutoff. The procedure was repeated four times in total to obtain 60 g of dispersion of Ag nanoplatelets in water. After ultrafiltration was completed, 0.17 g of the formula [ka] (a mixture of CAS 80584-88-9 and 80584-89-0) was added to the dispersion. Ag content 28.9% w / w; yield about 89% based on total silver; solids (250°C) 33.5% w / w; silver purity based on solids at 250°C 86% w / w.

[0203] B-2d. Ultrafiltration in isopropanol The dispersion was further ultrafiltered in isopropanol. 60 g of the Ag nanoplatelet dispersion obtained after ultrafiltration in water was placed in a Millipore Amicon 8400 stirred ultrafiltration cell and diluted to a weight of 300 g with isopropanol. The dispersion was ultrafiltered to a volume of about 50 mL using a polyethersulfone (PES) membrane with a cut-off value of 500 kDa. This procedure was repeated a total of four times to obtain a dispersion of 72 g of Ag nanoplatelets in isopropanol. Ag content 24.1% w / w; solids (250°C) 25.7% w / w; silver purity based on solids at 250°C 93.5% w / w. UV-Vis-NIR spectrum in water, 9.8 * 10 -5 The Ag concentration was recorded in M. max =700nm; maximum extinction coefficient ε=10200L / (cm * mol Ag), FWHM = 340 nm. Number average particle diameter 93±40 nm, number average particle thickness 16±2.5 nm.

[0204] B-3. ​​Preparation of Dispersion D1 a) Surface modification of Ag nanoplatelets 50 g (12.85 g solids) of the Ag nanoplatelet dispersion obtained as described in item B-2d was placed in a 250 mL round bottom flask under argon atmosphere at 23° C. 2.05 g of a 5% w / w solution of carbon disulfide in absolute ethanol was added and the mixture was stirred for 5 min, followed by the addition of 2.77 g of a 5% w / w solution of diethanolamine in absolute ethanol. The mixture was stirred for 1 h at 23° C., then 2.77 g of a 5% w / w solution of diethanolamine in absolute ethanol was added and stirring was continued for 30 min. UV-Vis-NIR spectrum of water with Ag concentration of 9.8 * 10 -5 Recorded at M. λ max =704nm.

[0205] b) Solvent exchange To the dispersion obtained in step a) was added 15.0 g of ethyl 3-ethoxypropionate. The mixture obtained was concentrated on a rotary evaporator at a pressure of 40 mbar and a bath temperature of 40° C. until no further solvent was distilled off. The weight of the obtained dispersion was adjusted to 32.1 g by addition of ethyl 3-ethoxypropionate (corresponding to a calculated total solids content of 41.2% w / w).

[0206] B-4 Preparation of Dispersion D2 a) Surface modification of Ag nanoplatelets 50 g (12.85 g solid) of the Ag nanoplatelet dispersion obtained as described in item B-2d was placed in a 250 mL round bottom flask under argon atmosphere at 23° C. 2.05 g of a 5% w / w solution of carbon disulfide in absolute ethanol was added and the mixture was stirred for 5 min, followed by the addition of 2.77 g of a 5% w / w solution of diethanolamine in absolute ethanol. After the mixture was stirred for 1 h at 23° C., 2.77 g of a 5% w / w solution of diethanolamine in absolute ethanol was added and stirring was continued for 30 min. UV-Vis-NIR spectrum of water with Ag concentration of 9.8 * 10 -5 Recorded at M. λ max =704nm.

[0207] b) Solvent exchange To the dispersion obtained in step a) was added 15.0 g of 7-oxabicyclo[4.1.0]hept-3-ylmethyl 7-oxabicyclo[4.1.0]heptane-3-carboxylate (CAS number: 2386-87-0). The mixture obtained was concentrated on a rotary evaporator at a pressure of 40 mbar and a bath temperature of 40° C. until no further solvent was distilled off. The weight of the obtained dispersion was adjusted to 32.1 g (corresponding to a calculated total solids content of 41.2% w / w) by adding 7-oxabicyclo[4.1.0]hept-3-ylmethyl 7-oxabicyclo[4.1.0]heptane-3-carboxylate (CAS: 2386-87-0).

[0208] C. Preparation of UV-Vis radiation curable screen printing inks (SP1-SP10) and top-coating inkjet inks (IJ1-IJ14) C1. UV-Vis radiation cationic or hybrid curable screen printing inks (SP1-SP10) [Table 1] JPEG2024544564000045.jpg66149 [Table 2]

[0209]

[0207] All ingredients listed in Table 1B except for Dispersions D1 / D2 were mixed and dispersed at room temperature using a Dispermat (model CV-3) at 2000 rpm for 10 minutes to obtain 20 g of each composition.

[0210]

[0208] 20 wt-% of the dispersions (D1 / D2) were independently added to 80 wt-% of each composition and dispersed at room temperature using a Dispermat (model CV-3) for 5 minutes at 800-1000 rpm to obtain 5 g of each UV-Vis radiation cationic or hybrid curable screen printing ink (SP1-SP10).

[0211] C2. Top coating inkjet ink (IJ1~IJ14) [Table 3] [Table 4]

[0212] Top-coating inkjet inks containing more than one component (IJ5, IJ7, IJ9 and IJ10) were prepared independently by mixing the components using a Dispermat CV-3 for 10 min at room temperature at 1000 rpm. The viscosity of the top-coating inkjet inks was measured at 1000 s using a rotational viscometer DHR-2 (TA Instruments) with a cone-plane geometry and a diameter of 40 mm. -1 , determined at 25°C.

[0213] Preparation and evaluation of security features D1. Preparation of security features (E1-E91 and C1-C28) Step a): The UV-Vis radiation curable screen printing inks SP1 to SP10 described in Table 1B were applied by hand independently to a piece of transparent window polymer substrate (x20) (Guardian, thickness 75 μm, supplied by CCL Secure, dimensions 60 mm x 60 mm) using a 160 threads / cm screen to obtain a coating layer (x10) having a thickness of 7 to 10 μm and forming a square with dimensions of 50 mm x 50 mm.

[0214] After step a), step b): the top-coating inkjet inks IJ1 to IJ14 listed in Table 2B were applied independently to the coating layer (x10) obtained in step a) by a DOD (drop-on-demand) inkjet printing process using a KM1024i inkjet head (Konica Minolta, 360 dpi) to obtain one or more indicia (x30) having the shape of a square with dimensions of 30 mm x 30 mm, said indicia (x30) being in the center of the square formed by the coating layer (x10) obtained in step a).

[0215] After step b), step c): The coating layer (x10) obtained after step a) and the inkjet printed indicia (x30) obtained after step b) are irradiated with UV-LED lamps from OmniCure® (Type AC4 50×25 mm, 385 nm, 8 W / cm 2 ) for approximately 0.5 seconds.

[0216]

[0213] This method allowed the production of security features according to the comparative method (C1 to C28) and according to the method of the invention (E1 to E91), each of which included a first area made of a cured covering layer (x10) devoid of one or more cured inkjet printed indicia (x30) and a second area made of a combination of a cured coating layer (x10) and one or more cured inkjet printed indicia (x30). The first area thus corresponds to a peripheral zone of the security feature having a width of about 10 mm, while the second area corresponds to a central zone of dimensions 30 mm x 30 mm.

[0217]

[0214] The determination of the ink laydown of one or more indicia (x30) made of top-coating inkjet ink applied to the coating layer (x10) was performed using a linear regression method. Four inkjet ink laydowns were experimentally measured (points 1-4 in Figure 3B) and a linear regression line with a 0-intercept was established based on these experimentally obtained inkjet ink laydowns. The inkjet ink laydown (g / m2) for all examples and comparative examples was 2 ) was calculated from this linear function. The procedure is as follows: i) The following parameters were introduced into the software driving the Konica Minolta inkjet printhead described above: resolution 360 dpi; dpd (drops per dot): 1 for point 1, 3 for point 2, 5 for point 3 and 7 for point 4; grey level: 100%; print geometry: 30mm x 30mm jet black square; ii) The UV-Vis radiation cationic curable screen printing ink SP1 (Table 1B) was applied independently to the substrates (x20) (size=70mm×70mm) described above in step a) to produce coating layers (x10) (size=30mm×30mm), and then each substrate (x20) including coating layer (x10) was weighed independently using an analytical balance (Mettler Toledo XS64). Four sets (i.e. one set for each point 1-4) of three samples were prepared and the average value was calculated for each set (x10+x20). The average values ​​are shown in Figure 3A; iii) top-coating inkjet ink IJ11 (Table 2B) was applied at 35° C. in the shape of one or more indicia (x30) described above (square with dimensions 30 mm×30 mm) with four different dpd values ​​1, 3, 5 and 7 (producing points 1, 2, 3 and 4, respectively, and shown in FIG. 3B) on top of the coating layer (x10) obtained in ii) at an image grey level of 100%; then each substrate (x20) including said coating layer (x10) and said one or more indicia (x30) was weighed using the same analytical balance as described above. The average value of three samples was calculated for each set (x10+x20+x30) and is shown in FIG. 3A; iv) The average value of the top coating inkjet ink deposition (x30) was calculated by subtracting the average weight (x10+x20) obtained in ii) from the average weight in iii) (i.e., the average weight (x10+x20+x30); v) For each set corresponding to the samples at points 1, 2, 3 and 4 (FIG. 3A), the inkjet ink deposition [g / m 2 iv) the average inkjet ink deposition amount obtained in step iv) on a known printing area (30 × 30 mm, or 0.000900 m 2 ) was obtained by dividing vi) A linear regression line with a 0-intercept (FIG. 3B) was established with the dpd values ​​on the x-axis and the inkjet ink deposition amount obtained in v) on the y-axis. The slope of the linear function so obtained was 3.8464, with an R 2The -value was 0.9996. The graph shown in FIG. 3B presents the values ​​obtained from the weight measurements (1-7 dpd) as a scatter plot with a linear regression line: Weighed ink deposition amount [g / m 2 ]=f(dpd value) The linear function and R 2 The measured ink adhesion amount [g / m 2 ]=3.8464 * is the dpd value, and R 2 is 0.9996. The table shown in Figure 3A discloses the numerical values ​​(gravimetric measurements) and the values ​​calculated from the linear function (last column).

[0218]

[0215] Ink adhesion amount (g / m) for all examples and comparative examples 2 ) was calculated from the linear function provided. For ink coverage corresponding to (theoretical) dpd values ​​less than 1, the grey level (%) of the inkjet printed image mentioned in i) was reduced. The relationship between the dpd value, the image grey level (%) of the printed image and the calculated ink coverage (g / m 2 ) are reported in the table.

[0219]

[0216] The following was prepared using the methods described in steps a) through c) above: Comparative method examples C1-C4 and inventive method examples E1-E28, where the UV-Vis cationic curable screen printing ink SP4 (Table 1B) was used in step a) and the inkjet inks IJ11, IJ1, IJ12 and IJ7 (Table 2B) were used in step b), the time between steps b) and c) was fixed at about 0.5 s and the inkjet ink deposition was about 0.4 g / m 2 ~ approx. 26.9g / m 2 and the optical results of the obtained security features are reported in Table 3A-D; Comparative method examples C5-C8 and inventive method examples E29-E48, where UV-Vis hybrid curable screen printing ink SP9 (Table 1B) was used in step a) and inkjet inks IJ11, IJ1, IJ12 and IJ6 (Table 2B) were used in step b), the time between steps b) and c) was fixed at about 0.5 seconds and the inkjet ink deposition was about 0.4 g / m 2 ~Approx. 11.5g / m 2 and the optical results of the security features obtained are reported in Tables 3E-3H; Examples E49 to E58 according to the method of the present invention, where UV-Vis cationic curable screen printing inks SP1 to SP5 (Table 1B) are used in step a) and inkjet ink IJ11 (Table 2B) is used in step b), the time between steps b) and c) is fixed at about 0.5 s and the inkjet ink deposition is about 1.0 g / m 2 or about 11.5 g / m 2 and the obtained optical results of security features are reported in Table 4A; Examples E59 to E68 according to the method of the present invention, where UV-Vis hybrid curable screen printing inks SP6 to SP10 (Table 1B) are used in step a) and inkjet ink IJ11 (Table 2B) is used in step b), the time between steps b) and c) is fixed at about 0.5 seconds and the inkjet ink deposition is about 1.0 g / m 2 or about 11.5 g / m 2 and the obtained optical results of the security features are reported in Table 4B; Examples E69 to E74 according to the method of the present invention, where the UV-Vis cationic curable screen printing ink SP4 (Table 1B) is used in step a) and the inkjet inks IJ2 to IJ5 and IJ13 to IJ14 (Table 2B) are used in step b), the time between steps b) and c) is fixed at about 0.5 s and the inkjet ink deposition is about 1.0 g / m 2 and the obtained optical results of the security features are reported in Table 5A; Examples E75 to E83 according to the method of the present invention, where UV-Vis hybrid curable screen printing ink SP9 (Table 1B) is used in step a) and inkjet inks IJ2 to IJ5, IJ8 to IJ10 and IJ13 to IJ14 (Table 2B) are used in step b), the time between steps b) and c) is fixed at about 0.5 seconds and the inkjet ink deposition is about 1.0 g / m 2 and the optical results of the security features obtained are reported in Table 5B; Comparative method examples C9 to C18 and inventive method examples E84 to E87, where the UV-Vis cationic curable screen printing ink SP4 (Table 1B) was used in step a) and the inkjet ink IJ11 (Table 2B) was used in step b), with an inkjet ink deposition of about 1.0 g / m 2 or about 11.5 g / m 2 and the time between step b) and step c) is varied from about 0.5 seconds to about 100 seconds, and the optical results of the obtained security features are reported in Table 6A; and Examples E88 to E91 according to the inventive method and Examples C19 to C28 according to the comparative method, where the UV-Vis hybrid curable screen printing ink SP9 (Table 1B) was used in step a) and the inkjet ink IJ11 (Table 2B) was used in step b), with an inkjet ink deposition of about 1.0 g / m 2 or about 11.5 g / m 2 and the time between steps b) and c) was varied from about 0.5 seconds to about 100 seconds. The optical results of the obtained security function are reported in Table 6B.

[0220] D-2. Evaluation of optical properties

[0217] The optical properties of the security features obtained according to the comparative methods (C1 to C28) or according to the methods according to the invention (E1 to E91) were evaluated independently in reflection, transmission and visually using the techniques described below. The visual evaluation (both reflection and transmission) aims to reproduce the way an average person would observe a security feature on the street, while the evaluation using a specific device mimics very closely the machine detection routinely performed, for example in an ATM or a high-speed sorting machine.

[0221]

[0218] Evaluation in reflection was performed using a goniospectrometer (Goniospektrometer Codec WI-10 5&5, Phyma GmbH Austria) according to the following procedure: i) For each of the UV-Vis radiation cationic or hybrid curable screen printing inks (SP1 to SP10), a reference sample was obtained using the same method as described above in steps a) and c) (i.e. omitting the inkjet printing step b)). In other words, each reference sample consisted of a substrate (x20) comprising a cured coating layer (x10) lacking one or more inkjet printed indicia (x30); ii) L of the reference sample * a * b * Values ​​were determined at 0° to the normal with illumination at 22.5°. * (chroma or color saturation) value to a * and b * From the values, it was calculated according to the CIELAB (1976) color space:

number

number

[0222]

[0219] Transmitted light measurements were performed using a Datacolor 650 spectrophotometer (parameters: integrating sphere, diffuse illumination (pulsed xenon D65) and 8° field of view, analyzer SP2000, dual 256 diode array, wavelength range 360-700 nm, transmitted light sampling aperture size 22 mm). * -values ​​were obtained in the same manner as described above for reflectance measurements. * Values ​​are listed in the table. * Shown as:

[0223]

[0220] Visual evaluation in reflection was performed as follows: The contrast was observed under diffuse lighting (e.g. light coming through a window without direct sunlight), with the security feature substrate (x20) held perpendicular to the diffuse light source and the angle of view chosen such that the diffuse light is not blocked by the observer's head (meaning a vertical angle of about 70° to about 20°). The observer reported the contrast observed between the first area (x10) and the second area (x10+x30). The following scale was used: excellent, good, sufficient, insufficient. Insufficient contrast here means a security feature that cannot be easily assessed by the observer and is not suitable as a security feature. The visual assessment in reflection is reported in the table as visual contrast.

[0224]

[0221] The visual evaluation also involved observing each security feature in transmitted light with the naked eye. The following colors were observed and are reported as visual colors in the table below: Dull blue: blue coloration barely visible to visible; Blue: Intense blue coloration; and Deep Blue: The blue coloring is very intense.

[0225] E. Results E1. Variation in inkjet ink deposition amount (C1 to C8 and E1 to E48) (Tables 3A to 3H) [Table 5] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10] [Table 11] [Table 12]

[0226] As shown in Tables 3A-H, the method according to the invention allows the production of security features of high quality in terms of contrast and color properties in reflection and transmission, thus allowing easy recognition, and with a weight of about 0.8 g / m 2 A minimum inkjet ink coverage of at least about 1.0 g / m2 is required, which allows for sufficient contrast between the first and second regions for UV-Vis radiation cationic or hybrid curable screen printing inks (E1-E48) as shown by the values ​​and characteristics provided, as assessed visually and / or with a goniospectrometer. As shown in Tables 3A-H, a minimum inkjet ink coverage of at least about 1.0 g / m2 is required, which allows for sufficient contrast between the first and second regions for UV-Vis radiation cationic or hybrid curable screen printing inks (E1-E48). 2 (E1, E8, E15, E22, E29, E34, E39, E44) allow for the creation of security features that exhibit sufficient to good contrast by eye and by goniospectrometer and are at least about 1.9 g / m 2 The amount of light (E2, E9, E16, E23, E30, E35, E40, E45) has made it possible to create security features that exhibit good to excellent contrast.

[0227]

[0223] The security feature obtained by the method according to the invention is gold in reflection and blue to dark blue in transmission, the indicia or indicia (x30) appearing in reflection light brown to dark brown depending on the amount of ink applied. Transmission in the visible range is largely unaffected by the indicia or indicia, making said indicia or indicia easy to very easy to observe in reflection but almost invisible in transmission.

[0228] E2. Variation in the composition of UV-Vis curable screen printing inks (E49~E68) [Table 13] [Table 14]

[0229]

[0224] As shown in Tables 4A-B, UV-Vis curable cationic screen printing inks (SP1-SP5) comprising cycloaliphatic epoxides or mixtures of cycloaliphatic epoxides and one or more UV-Vis radiation curable compounds and UV-Vis curable hybrid screen printing inks (SP6-SP10) comprising cycloaliphatic epoxides or mixtures of cycloaliphatic epoxides and one or more UV-Vis radiation curable compounds and radically curable compounds are suitable for producing high quality security features with the method according to the invention. Said UV-Vis curable screen printing inks may contain or be devoid of solvent. The security features obtained with the method according to the invention are gold in reflection and blue to dark blue in transmission, while the indicia (x30) appear light brown to dark brown depending on the amount of ink deposition. Transmission in the visible range is largely unaffected by the indicia or indicia, making it easy to very easy to observe the indicia or indicia in reflection but barely visible in transmission.

[0230] E3. Variation in composition of top-coating inkjet inks (E69-E83) [Table 15] [Table 16] TIFF2024544564000063.tif28149

[0231]

[0225] As shown in Table 5A, the UV-Vis curable cationic screen printing inks used in combination with a top-coating inkjet ink comprising one or more cationically curable monomers (IJ1-5); or one or more radically curable monomers and a free radical photoinitiator (IJ7); or one or more hybrid monomers (IJ11); or one or more solvents (IJ12-IJ14) are suitable for producing high quality security features with the method according to the invention. As shown in Table 5B, the UV-Vis curable hybrid screen printing inks used in combination with a top-coating inkjet ink comprising one or more cationically curable monomers (IJ1-5); or one or more radically curable monomers (IJ6-IJ10); or one or more hybrid monomers (IJ11); or one or more solvents (IJ12-IJ14) are suitable for producing high quality security features with the method according to the invention.

[0232]

[0226] The security feature obtained by the method according to the invention is gold in reflection and blue to dark blue in transmission, while the indicia (x30) appear light brown to dark brown depending on the amount of ink applied. Transmission in the visible range is largely unaffected by the indicia or indicia, making it easy to very easy to observe said indicia or indicia in reflection, but barely visible in transmission.

[0233] E4. Variation of time between step b) and step c) (C9-C28 and E84-E89)

[0227] As shown in Tables 6A-6B, the time between step b) of at least partially applying the top coating inkjet ink onto the coating layer (x10) and step c) of curing the coating layer (x10) made of UV-Vis curable screen printing ink and indicia (x30) was varied from about 0.5 seconds to about 100 seconds.

[0234]

[0228] In addition to the optical properties measured or visually evaluated as described in item D-2, a visual evaluation of the resulting resolution was performed for comparative method examples (C9-C28) and inventive method examples (E84-E89), which were prepared as described above, except that the indicia or indicia (x30) was in the shape of the name "SICPA" in gradually decreasing font sizes instead of a square. As shown in Figure 1A, security features were prepared having one or more indicia (130), in particular one indicia, in the shape of the name "SICPA" (arial font) in different sizes. The indicia had an overall size of 30 mm by 20 mm, the first line of "SICPA" was printed in Arial size 8 (name height: 2.1 mm), the second line was printed in size 6 (name height: 1.7 mm), the third line was printed in size 5 (name height: 1.3 mm), the fourth line was printed in size 4 (name height: 1.1 mm) and the fifth line was printed in size 3 (name height: 0.8 mm). Visual assessment of resolution was as follows: Excellent: Lines printed in the smallest font (Arial 3) are easily legible, and the resolution is close to that obtained with a conventional laser printer (resolution: 600 dpi) for the same font and font size (Figure 1B). Good: slight enlargement of characters is observable, and lines printed in the smallest characters (Arial 3) are still legible Sufficient: The enlargement of the characters is clearly observable; the lines printed in the smallest characters (Arial 3) are barely legible, while the lines printed in slightly larger characters (Arial 4) are easily legible. Poor: The text has been enlarged so that it appears diffuse; lines printed in the smallest type (Arial 3) are unreadable, while lines printed in slightly larger type (Arial 4) are just barely readable.

[0235] It is known that good to excellent resolution is required for the preparation of security features containing one or more complex indicia (e.g. portraits, photographs of grey levels or geometric figures containing intricate line patterns) as well as small size codes (e.g. 1-D codes or QR codes), while sufficient resolution is sufficient for printing simpler indicia (e.g. geometric patterns made of flat areas, numbers, letters or logos) as well as larger size codes. The resolutions evaluated according to the above described methods observed for security features obtained by the inventive method (Examples E84-E91) and the comparative methods (C9-C28) are shown in Tables 6A-6B. [Table 17] [Table 18]

[0236] As shown in Tables 6A-B, the method according to the invention allows the production of security features of high quality in terms of contrast and color properties in reflection and transmission, thus allowing easy recognition, and having a weight of about 11.5 g / m 2 To obtain a sufficient resolution with an inkjet ink deposition of 100 μm, a time between steps b) and c) of less than 5 seconds, in particular less than 4 seconds or equal to about 3.5 seconds, is required.

[0237] A further example was prepared and is shown in Figure 2, where the security feature was prepared by applying the UV-Vis radiation hybrid curable screen printing ink SP3 by hand to a piece of transparent window (Guardian, 75 μm thick, supplied by CCL Secure, dimensions 60 mm x 60 mm) of a polymer substrate (220) using a 160 threads / cm screen to obtain a coating layer (210) having a thickness of 7-10 μm and forming a square of dimensions 50 mm x 50 mm, and top-coating inkjet ink IJ11 was applied on top of the screen printed layer (210) at 1 dpd (3.8 g / m) using a KM1024i inkjet head (Konica Minolta, 360 dpi) by a DOD (drop on demand) inkjet printing process. 2 ) was applied to the coating layer (210) to obtain one or more indicia (230), in particular one indicia, having the shape of a QR code (dimensions: 24 mm x 24 mm). After said inkjet printing step, the screen printed layer (210) and the inkjet printed indicia (230) were then subjected to a UV-LED lamp from Omnicure® (type AC4 50 x 25 mm, 385 nm, 8 W / cm 2 ) for approximately 0.075 seconds, with the time between the inkjet printing step and the curing step being fixed at 0.5 seconds.

Claims

1. 1. A method for producing a security feature exhibiting one or more indicia (x30) on a substrate (x20), comprising the steps of: Step a) of applying a UV-Vis radiation curable ink to a surface of a substrate (x20) to form a coating layer (x10), wherein the UV-Vis radiation curable ink is in a first liquid state, and the UV-Vis radiation curable ink comprises: i) 7.5 wt. % to 20 wt. % of a compound of general formula (V) 【Chemical 1】 [In the formula, residue R Ａ is a C substituted with a hydroxy group ２ -C ４ is an alkyl group; residue R Ｂ is C １ -C ４ C substituted with alkyl and hydroxy groups ２ -C ４ alkyl groups; Cat ＋ is the general formula ＋ NH ２ R Ｃ R Ｄ is the ammonium cation, where residue R Ｃ is a C substituted with a hydroxy group ２ -C ４ is an alkyl group; residue R Ｄ is C １ -C ４ C substituted with alkyl and hydroxy groups ２ -C4 alkyl group; ii) 45 wt-% to 80 wt-% of a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds; iii) one or more cationic photoinitiators; iv) perfluoropolyether surfactants functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, methacrylate, and trialkoxysilyl; v) 3 wt-% to 12 wt-% of a polyvinyl chloride copolymer containing at least 60 wt-% vinyl chloride; and optionally vi) 25 wt-% or less of one or more organic solvents wherein the weight percentage is based on the total weight of the UV-Vis radiation curable ink; After step a), a step b) of at least partially applying a top coating composition onto the coating layer (x10) by a non-contact fluid microdispensing technique, said top coating composition being applied in the form of one or more indicia (x30), said one or more indicia (x30) having a density of 0.8 g / m ２ Step b) having a higher ink deposition; After step b), a step c) of curing the coating layer (x10) and the one or more indicia (x30) in one or more curing units (x50), The time between steps b) and c) is less than 5 seconds. method.

2. The method of claim 1, wherein the one or more indicia (x30) have an ink coverage equal to or greater than 1.0 g / m 2 .

3. A method as described in claim 1 or 2, wherein the time between steps b) and c) is equal to or less than 3.5 seconds.

4. 3. The method of claim 1 or 2, wherein the one or more UV-Vis radiation curable compounds comprise one or more cationically curable monomers selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers other than cycloaliphatic epoxides, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl-containing compounds, and mixtures thereof.

5. 5. The method of claim 4, wherein the one or more UV-Vis radiation curable compounds comprise one or more cationically curable monomers selected from the group consisting of vinyl ethers, cyclic ethers other than cycloaliphatic epoxides, and mixtures thereof.

6. 3. The method of claim 1 or 2, wherein the one or more UV-Vis radiation curable compounds comprise one or more radically curable monomers and / or oligomers, and the UV-Vis radiation curable ink further comprises vii) one or more free-radical photoinitiators.

7. 3. The method of claim 1, wherein the UV-Vis radiation curable ink comprises a perfluoropolyether surfactant in an amount of 0.025 wt-% to 5 wt-%, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

8. 3. The method of claim 1 or 2, wherein the top coating composition comprises one or more cationically curable compounds, one or more hybrid curable compounds, one or more solvents, one or more radically curable compounds, or a mixture thereof.

9. 9. The method of claim 8, wherein the cationically curable compound is selected from the group consisting of vinyl ethers, glycidyl ethers, oxetanes, and mixtures thereof; and / or the one or more hybrid curable compounds are hydroxy-modified or (meth)acrylate-modified vinyl ethers; and / or the one or more solvents are selected from the group consisting of alcohols, ketones, glycols, glycol ethers, ether esters, glycol ether esters, alkylene carbonates, and mixtures thereof; and / or the one or more radically curable compounds are selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, and mixtures thereof.

10. 3. The method of claim 1, wherein the silver nanoplatelets have a number average diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a number average thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the number average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy.

11. The method of claim 10, wherein the number average diameter of the silver nanoplatelets is in the range of 70 to 120 nm with a standard deviation of less than 50%, the number average thickness of the silver nanoplatelets is in the range of 8 to 25 nm with a standard deviation of less than 30%, and the average aspect ratio of the silver nanoplatelets is greater than 2.

5.

12. 3. The method of claim 1 or 2, wherein the surface stabilizer having general formula (V) is present in an amount of 0.5% to 5% by weight percent (wt-%) of the silver nanoplatelets of i).

13. 3. The method according to claim 1 or 2, wherein the step c) of curing the coating layers (x10) and the one or more indicia (x30) is carried out in one or more curing units (x50) selected from the group consisting of mercury lamps, UV-LED lamps and sequences thereof.

14. 14. The method of claim 13, wherein step c) is performed with one or more UV-LED lamps.

15. 3. The method according to claim 1 or 2, wherein said one or more indicia (x30) are selected from the group consisting of codes, symbols, alphanumeric symbols, motifs, geometric patterns, letters, words, numbers, logos, figures, portraits and combinations thereof.

16. 3. The method according to claim 1 or 2, wherein step a) is performed by a process selected from the group consisting of a rotogravure printing process, a flexographic printing process and a screen printing process, and / or step b) is performed by an inkjet printing process.

17. The method of claim 16, wherein step b) is performed by a drop-on-demand inkjet printing process.

18. The method of claim 1 or 2, wherein the UV-Vis radiation curable ink is applied to transparent or partially transparent areas of the substrate (x20).

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