Method for creating a dichroic security mechanism for protecting valuable documents - Patent Application 20070122999

Abstract

The present invention provides a method for manufacturing a security feature for protecting 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 manufacturing method includes the following steps: a) printing a specific UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a value document substrate; 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 so 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. The manufacturing method according to the present invention allows for the successful manufacture of a security feature exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, and is particularly useful in the commercial printing of value documents.

Description

Detailed Description of the Invention

[0001] [Field of the Invention] The present invention relates to the technical field of methods for producing 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, for protecting valuable documents.

[0002] [Background of the invention] The quality of color photocopying and printing is constantly improving, and in an attempt to protect security documents such as banknotes, value documents or cards, transport boarding passes or cards, tax banderols and product labels from counterfeiting, alteration or illegal duplication, it has become conventional practice to incorporate various security features into these documents.

[0003] For example, security features for security documents can generally be categorized as "covert" and "overt" security features. The protection provided by covert security features is based on the concept that such features are difficult to detect and typically require specialized equipment and knowledge, whereas "overt" security features are readily detectable by unaided human senses; for example, such features are visible and / or detectable via touch, but remain difficult to manufacture and / or replicate. However, overt security features rely heavily on easy recognition as security features. Most users, especially those without prior knowledge of the security features of a protected document or article, will only actually perform a security check based on the security features if they have actual knowledge of the security features' existence and nature.

[0004] A special role in protecting valuable documents is played by dichroic security mechanisms, which exhibit a first color when viewed in incident light and a second color different from the first when viewed in transmitted light. To create a striking effect and attract the public's attention, the first and second colors must have an appealing visual appearance, such as blue, metallic yellow, magenta, and green, and a strong color contrast (e.g., blue / metallic yellow, green / metallic yellow, purple / metallic yellow).

[0005] Such a dichroic security mechanism is disclosed in U.S. Patent Publication No. 2012 / 0242075, which describes a see-through security element including a thin-film element having a multilayer structure and a carrier that appears gold in incident light and blue in transmitted light. The thin-film element includes at least two semi-transparent mirror layers and at least one dielectric spacer layer disposed between the at least two mirror layers. The manufacturing process for the see-through security element is time-consuming, as it involves thermal deposition, electron beam evaporation, or sputtering of each of the at least three layers contained in the thin-film element on the carrier.

[0006] WO 2011064162 also describes a dichroic security or decorative element comprising a substrate and a coating comprising platelet-shaped transition metal particles, the longest dimension of which is 15 nm to 1000 nm along its edge length and a thickness of 2 nm to 500 nm, on at least a portion of the substrate surface. Hand-coating of a UV-curable ink containing silver platelets and either a solvent-based vehicle or a vehicle containing a radically curable monomer and a free-radical photoinitiator, in a silver platelet-to-vehicle weight ratio of 3:1.1 on a transparent substrate, results in a security or decorative element that exhibits a blue color in transmitted light and a gold / copper or gold / bronze color in reflected light. The high concentration of silver platelets in the ink used to obtain the security or decorative element described in WO 2011064162 is detrimental to the mechanical resistance of the resulting security or decorative element and, further, makes the manufacturing process for the element expensive. Furthermore, the mechanical resistance of the security or decorative elements described in WO201106416 is compromised by the use of UV radical curable or solvent-based inks, as is well known to those skilled in the art, resulting in a cured coating with limited mechanical resistance. Since mechanical resistance is an essential property of a security element and the manufacturing process described in WO201106416 is time-consuming and rather expensive, the technology described by said document is not suitable for the production of dichroic security features, and in particular not for the industrial production of dichroic security features on value documents.

[0007] Typically, industrial printing of value documents requires high printing speeds of approximately 8,000 sheets per hour, with a significant number of value documents being produced from each sheet. For illustrative purposes, in the field of banknote printing, up to 55 value documents, each containing one or more security features, can be produced from a single sheet. To be suitable for implementation on a production line, it is essential that the production process for each printable security feature present on a value document meets the high-speed requirements of industrial printing of value documents.

[0008] Therefore, there is a need for an easy, low-cost process for rapid (i.e., industrial speed) manufacturing of dichroic security features that exhibit a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light on value documents.

[0009] [Summary of the Invention] It is therefore an object of the present invention to provide an easy and cost-effective method for rapid (i.e., industrial) manufacturing of security features for protecting valuable documents, said security features exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light. This is achieved by the method claimed in the present application, which method comprises the following steps: a) printing a UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a substrate of a value document, preferably by screen printing, rotogravure or flexographic printing, to provide an ink layer; 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 so that the ink layer exhibits a metallic yellow color when viewed under incident light; c) UV-Vis curing the ink layer obtained in step b) to form the security feature. Including, UV-Vis ray curable ink i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii) about 40% to about 75% by weight of either a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more UV-Vis radiation curable compounds other than a cycloaliphatic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii) and vi) are based on the total weight of the UV-Vis radiation curable ink.

[0010] The manufacturing method according to the present invention allows for the production in an expedient manner of security features on value documents that exhibit a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, thereby meeting the high-speed requirements of industrial printing of value documents. The attractive visual appearance and the contrast between the blue color when viewed in transmitted light and the metallic yellow color when viewed in incident light make the security features obtained via the process according to the present invention conspicuous, thereby drawing the attention of the public to the security features and aiding in locating and recognizing the security features on value documents and in authenticating value documents containing the security features. Thus, the manufacturing method according to the present invention provides dichroic security features with an attractive visual appearance and high value perception.

[0011] Preferably, the concentration of silver nanoplatelets in the UV-Vis radiation curable ink is about 5% to about 20% by weight, preferably about 7.5% to about 17.5% by weight, and more preferably about 10% to about 15% by weight, based on the total weight of the UV-Vis radiation curable ink. The concentration of silver nanoplatelets in the UV-Vis radiation curable ink used in the method according to the present invention is significantly lower than the concentration of silver platelets used in inks known in the art. Thus, the manufacturing method claimed herein allows for the cost-effective production of dichroic security features with optical effects similar to those of the prior art, but with significantly improved mechanical resistance properties.

[0012] In one embodiment according to the present invention, the UV-Vis radiation curable ink used in the method of manufacture claimed and described herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-1) about 40% by weight to about 75% by weight of an alicyclic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-1) and vi) are based on the total weight of the UV-Vis radiation curable ink, cationically curable ink.

[0013] In a further embodiment according to the present invention, the UV-Vis radiation curable ink used in the method of manufacture claimed and described herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-2) about 40% to about 75% by weight of a mixture of a cycloaliphatic epoxide and one or more cationically curable monomers other than a cycloaliphatic epoxide, wherein the ratio of the weight percent (wt%) of the cycloaliphatic epoxide present in the ink to the weight percent (wt%) of the one or more cationically curable monomers other than a cycloaliphatic epoxide present in the ink is greater than about 1.1:1; and iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-2) and vi) are based on the total weight of the UV-Vis radiation curable ink, cationically curable ink.

[0014] The UV-Vis radiation curable ink used in the manufacturing method claimed and described herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-3) about 40% to about 75% by weight of a mixture of a cycloaliphatic epoxide and one or more radically curable monomers and / or oligomers other than a cycloaliphatic epoxide, wherein the ratio of the weight percent (wt%) of the one or more radically curable monomers and / or oligomers present in the ink to the weight percent (wt%) of the cycloaliphatic epoxide present in the ink is less than about 1.6:1; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; ix) one or more free radical photoinitiators, and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-3) and vi) may be based on the total weight of the UV-Vis ray curable ink.

[0015] In an alternative embodiment, the UV-Vis radiation curable ink used in the manufacturing method claimed and described herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-4) about 40% by weight to about 75% by weight of a mixture of an alicyclic epoxide, one or more cationically curable monomers other than the alicyclic epoxide, and one or more radically curable monomers and / or oligomers, the ratio of the weight percent (wt %) of the one or more radically curable monomers and / or oligomers present in the ink to the sum of the weight percent (wt %) of the cycloaliphatic epoxide present in the ink and the weight percent (wt %) of the one or more cationically curable monomers other than the cycloaliphatic epoxide present in the ink is less than about 1.6:1; the ratio of the weight percent (wt%) of cycloaliphatic epoxide present in the ink to the weight percent (wt%) of one or more cationically curable monomers other than cycloaliphatic epoxide present in the ink is greater than about 1.1:1; a mixture of iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; ix) one or more free radical photoinitiators, and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-4) and vi) are based on the total weight of the UV-Vis radiation curable ink. The ink may be a UV-Vis ray hybrid curable ink.

[0016] Advantageously, the methods claimed and described herein that rely on the use of the UV-Vis radiation cationically curable inks described herein or the use of the UV-Vis radiation hybrid curable inks described herein provide security features with improved mechanical properties compared to similar security features known in the art that are obtained from UV radically curable inks or solvent-based inks, particularly UV radically curable inks or solvent-based inks containing high concentrations of silver nanoplatelets.

[0017] In order to provide a valuable document with anti-smudge properties and / or to protect the security mechanism from physical and chemical attack from the environment, the manufacturing method claimed in the present application preferably comprises steps f) and g) which are carried out after step c): f) applying a curable protective varnish onto the substrate, preferably by a printing process, to form a varnish layer; g) curing the varnish layer obtained in step f) to form a protective coating; Further includes:

[0018] [Detailed explanation] (definition) The following definitions should be used to interpret the meaning of the terms discussed in the description and recited in the claims.

[0019] As used herein, the article "a / an" denotes one and more than one and does not necessarily limit the referenced noun to the singular.

[0020] As used herein, the term "about" means that the quantity or value in question may be the specified specific value or another value in its vicinity. Generally, when the term "about" refers to a specific value, it is intended to represent a range of ±5% of that value. As an example, the phrase "about 100" represents a range of 100±5, i.e., a range of 95 to 105. Preferably, the range represented by the term "about" represents a range of ±3% of the value, more preferably a range of ±1%. Generally, when the term "about" is used, it can be expected that similar results or effects of the present invention can be obtained within a range of ±5% of the indicated value.

[0021] As used herein, the term "and / or" means that all or only one member of the group may be present. For example, "A and / or B" means "only A or only B, or both A and B." In the case of "only A," the term also covers the possibility that B is absent, i.e., "only A and no B."

[0022] 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 compounds other than A. However, the term "comprising" also covers the more restrictive meanings of "consisting essentially of" and "consisting of," as specific embodiments thereof. For example, a "solution comprising A, B, and optionally C" may consist (essentially) of A and B, or consist (essentially) of A, B, and C.

[0023] Where the description of the present invention refers to "preferred" embodiments / features, combinations of these "preferred" embodiments / features are considered to be disclosed as long as the particular combination of "preferred" embodiments / features makes technical sense.

[0024] As used herein, the term "one or more" means one, two, three, four, etc.

[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 to 600 nm, and more preferably 200 to 400 nm).

[0026] Surprisingly, there is provided a method for producing a security feature for protecting a valuable document, said security feature exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, said method comprising the steps of: a) printing a UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a substrate of a value document, preferably by screen printing, rotogravure or flexographic printing, to provide an ink layer; 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 so that the ink layer exhibits a metallic yellow color when viewed in incident light; c) UV-Vis curing the ink layer obtained in step b) to form the security feature. Including, UV-Vis ray curable ink, i) silver nanoplatelets having an average diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, an average thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and an average aspect ratio of greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii) about 40% to about 75% by weight of either a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more UV-Vis radiation curable compounds other than a cycloaliphatic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii) and vi) are based on the total weight of the UV-Vis radiation curable ink. It has been found that the method allows for convenient and cost-effective production in a single printing step of a dichroic security feature with an attractive visual appearance and high value perception on the value document. The production method meets the high speed requirements of industrial printing of value documents without affecting the optical properties exhibited by the dichroic security feature on the value document.

[0027] The security features realized by the manufacturing method claimed herein exhibit a blue color when viewed in transmitted light, i.e., in transmission. For the purposes of the present invention, viewing in transmitted light means that the security feature is illuminated from one side, for example, by holding the security feature against daylight or in front of a light source and viewing from the other side. The blue color is observed independently from which side the security feature is viewed in transmitted light. For the purposes of the present invention, a security feature exhibiting a blue color is one that has a saturation value C (corresponding to a measure of color intensity or color saturation) greater than 20. * A strong to very strong blue color is one that exhibits a saturation value C above 30. * It is characterized by the saturation value C * is a according to the CIELAB (1976) color space * value and b * is calculated from the value, where:

number

[0028] The above 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 equipped with a dual 256-element diode array corresponding to wavelengths in the range 360 ​​nm to 700 nm, transmission sampling aperture size 22 mm).

[0029] The security features provided by the manufacturing methods claimed herein exhibit a metallic yellow or gold color when viewed in incident light (i.e., when reflected). In this patent application, the terms "metallic yellow" and "gold" are used interchangeably. For purposes of the present invention, "viewed in incident light" means that the security feature is illuminated from one side and viewed from the same side. The metallic yellow color is observed independently from which side the security feature is viewed in incident light. For purposes of the present invention, a security feature exhibiting a metallic yellow or gold color is a security feature that exhibits a metallic yellow or gold color according to the CIELAB (1976) color space. * value and b * Saturation values ​​greater than 20, calculated from the C value * (corresponding to a measure of color intensity or color saturation), wherein:

number

[0030] Step a) of the manufacturing method according to the present invention involves printing a UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a value document substrate to provide an ink layer. The manufacturing method according to the present invention claimed herein allows access to a security feature that displays a metallic yellow color in incident light and a blue color, particularly a strong to very strong blue color, in transmitted light in a single printing step. As used herein, the term "printing" refers to any printing process suitable for printing the UV-Vis radiation curable ink described herein onto a value document substrate. In particular, the term "printing" refers to a printing process selected from the group consisting of screen printing, rotogravure, flexography, pad printing, inkjet printing, and spray printing. Preferably, the UV-Vis radiation curable ink is printed onto the transparent or partially transparent area of ​​the value document substrate by screen printing, rotogravure, or flexography, more preferably by screen printing.

[0031] Screen printing (also known in the art as silk screen printing) is a printing technique that typically uses a screen made of woven mesh to carry an ink-blocking stencil. The attached stencil forms open areas in the mesh that transfer ink onto the substrate as a sharp-edged image. A squeegee moves across the screen bearing the ink-blocking stencil, forcing the ink to pass through the woven mesh threads within the open areas. A key feature of screen printing is that a greater thickness of ink can be applied to the substrate compared to other printing techniques. Therefore, screen printing is also preferred when ink deposits with thicknesses of approximately 10-50 μm or greater are required, thicknesses that cannot be easily achieved with other printing techniques. Generally, screens are made of a porous, finely woven fabric, called a mesh, stretched over a frame, such as aluminum or wood. Currently, most meshes are made of synthetic or man-made materials, such as steel threads. Preferred synthetic materials are nylon or polyester threads.

[0032] In addition to screens based on woven meshes based on synthetic or metallic threads, screens have been developed from solid metal sheets with a grid of holes. Such screens are prepared by a process that includes electrolytically forming a metal screen by forming a screen skeleton on a matrix with a separating agent in a first electrolytic bath, stripping the formed screen skeleton from the matrix, and subjecting the screen skeleton to electrolysis in a second electrolytic bath to deposit metal on the skeleton.

[0033] 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 reciprocating process to perform a print run. First, the screen is moved into position above the substrate, a squeegee is pressed against the mesh and drawn over the image area, and then the screen is lifted off the substrate to complete the process. In a flatbed printer, the substrate to be printed is typically placed on a horizontal print bed parallel to the screen. Cylinder pressure attaches the substrate to the cylinder. Flatbed and cylinder screen printing processes are discontinuous processes, and as a result, are generally limited to speeds of up to 45 m / min for web or 3,000 sheets / hour for sheet-fed processes.

[0034] Conversely, rotary screen printers are designed for continuous, high-speed printing. The screens used in rotary screen printers are thin-walled metal cylinders, typically obtained using the electroforming process described above or made from woven steel threads. The open-ended cylinders are capped at both ends and attached to blocks on the sides of the press. During printing, ink is pumped into one end of the cylinder, constantly maintaining a fresh cylinder. A squeegee is fixed inside the rotating screen, and squeegee pressure is maintained and adjusted to allow good, consistent print quality. An advantage of rotary screen printing is its speed, which can easily reach 150 m / min for web printing or 10,000 sheets / hour for sheet-fed processes.

[0035] Screen printing is described in detail, for example, in The Printing Ink Manual, R.H. Leech and R.J. Pierse, Springer Edition, 5th ed., pp. 58-62; Printing Technology, J.M.Adams and P.A.Dolin, Delmar Thomson Learning, 5th ed., pp. 293-328; and Handbook of Print Media, H. Kipphan, Springer, pp. 409-422 and 498-499.

[0036] As known to those skilled in the art, the term rotogravure refers to a printing process described, for example, in Handbook of Print Media, Helmut Kipphan, Springer Edition, p. 48. Rotogravure is a printing process in which image elements are engraved into the surface of a cylinder. Non-image areas are at a constant, original level. Prior to printing, the entire printing plate (non-printing and printing elements) is inked and saturated with ink. The ink is removed from the non-image area by 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 adhesive forces between the substrate and the ink, typically at pressures ranging from 2 to 4 bar. The term rotogravure does not encompass, for example, intaglio printing processes (also known in the art as engraved steel die or copperplate printing processes), which rely on different types of ink.

[0037] The flexographic printing process preferably uses a unit with a chambered doctor blade, an anilox roller, and a printing cylinder. The anilox roller advantageously has small cells whose volume and / or density determine the ink or varnish application speed. The chambered doctor blade contacts the anilox roller, filling the cells and simultaneously scraping off excess ink or varnish. The anilox roller transfers the ink to the printing cylinder, which ultimately transfers the ink to the substrate. The printing cylinder may be made of a polymeric or elastomeric material. Polymers are primarily used as photopolymers for plates, sometimes as seamless coatings on sleeves. Photopolymer plates are made from 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 solidify or harden the bottom of the plate. The plate is then flipped over, a negative of the job is attached to the uncured side, and the plate is further exposed to UV light. This solidifies the plate in the image areas. The plate is then processed to remove the unsolidified photopolymer from the non-image areas, lowering the plate surface in these non-image areas. After processing, the plate is dried and then given a post-exposure dose of UV light to cure the entire plate. Preparation of flexographic plate cylinders is described in Printing Technology, J.M.A. Dams and P.A. Dolin, Delmar Thomson Learning, 5th Edition, pp. 359-360.

[0038] As used herein, a "transparent or partially transparent region of a value document substrate" refers to a region of a value document substrate, wherein said region is characterized by an average transmittance within the visible range of at least 50%, preferably at least 70%, and more preferably at least 90%. The transparent or partially transparent region of the substrate and the remaining region of the substrate may be made of either 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 opening in the substrate made of a material different from the transparent or partially transparent material, results in a value document substrate made of a material different from the transparent or partially transparent region of the substrate and the remaining region of the substrate.

[0039] Materials for value document substrates include, but are not limited to, paper or other fibrous materials, such as cellulose, paper-containing materials, plastics and polymers, composite materials, and mixtures or combinations thereof. Typical paper, paper-like, or other fibrous materials are made from a variety of fibers, including, but not limited to, abaca, cotton, linen, wood pulp, and blends thereof. As known to those skilled in the art, cotton and cotton / linen blends are preferred for banknotes, while wood pulp is commonly used in 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), glycol-modified polyethylene terephthalate (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, but are not limited to, multilayer structures or laminates of paper and at least one plastic or polymer material, such as those described 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), glycol-modified polyethylene terephthalate (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 value document substrate can carry a primer layer on top of which a UV-Vis radiation curable ink is printed.The primer layer is 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.

[0040] In step b) of the manufacturing method of the present invention described herein, the ink layer obtained in step a) is heated at a temperature of about 55°C to about 100°C for at least 1 second, so that the ink layer exhibits a metallic yellow color when viewed in incident light. The heating step at a temperature of about 55°C to about 100°C for at least 1 second enables the alignment of the silver nanoplatelets contained in the ink layer at the ink layer-air interface and the ink layer-substrate interface, resulting in the proper formation of a thin layer of silver nanoplatelets at the interfaces, and the appearance of a metallic yellow color observed in incident light. The use of the specific UV-Vis radiation curable ink described herein prevents the formation of silver aggregates in the ink layer during the heating step. The formation of silver aggregates is detrimental to the appearance of a blue color in transmitted light. Comparison of Comparative Experiment C1 with Experiment E1 according to the present invention demonstrates that a minimum temperature of about 55°C is required during the heating step to exhibit a metallic yellow color in incident light and a strong blue color in transmitted light within at least 1 second. Heating the ink layer at a temperature of 50°C for 1 second produces a weak brown color in incident light, a color that is not noticeable to the general public and is therefore not suitable for a dichroic security mechanism for protecting valuable documents. The development of a metallic yellow color within 1 second is achieved by heating the ink layer at a temperature of about 55°C to about 100°C (see, for example, Experiments E1-E6 of the present invention). Thus, a manufacturing method according to the present invention, which relies on a combination of the specific UV-Vis radiation curable ink described herein and a heating step at a temperature of about 55°C to about 100°C of an ink layer printed, preferably by screen printing, rotogravure, or flexographic printing, more preferably by screen printing, allows for the achievement of an ink layer that exhibits a metallic yellow color in incident light and a blue color, particularly a strong to very strong blue color, in transmitted light, within a heating time as short as 1 second. The time required for the development of a metallic yellow color, at least 1 second, meets the high-speed requirements of industrial printing of valuable documents.

[0041] Increasing the heating temperature and / or heating time from about 55°C to about 100°C leads to higher saturation values ​​C in both reflected and transmitted light, as evidenced, for example, by experiments E1 to E6 and E31 to E39 according to the present invention. * Preferably, in step b), the ink layer is heated at a temperature of about 60° C. to about 90° C. for at least 1 second, more preferably at a temperature of about 70° C. to about 90° C. for at least 1 second, and even more preferably at a temperature of about 80° C. for at least 1 second. To meet the high speed requirements of industrial printing of valuable documents, preferably the heating time is about 10 seconds or less, more preferably about 6 seconds or less, for example, 5 seconds, 4 seconds, 3 seconds, 2 seconds, and 1 second.

[0042] The heating step can be carried out by exposing the substrate bearing the ink layer obtained in step a) for at least 1 second to a temperature of about 55°C to about 100°C provided by a heating element, such as a hot air tunnel, an infrared dryer, a heating plate, a heating cylinder, a microwave oven, a photonic curing tool, or a combination thereof. Preferred heating elements include a hot air tunnel, an infrared dryer, and a combination thereof.

[0043] In step c) of the claimed manufacturing method of the present invention, the ink layer obtained in step b) is subjected to UV-Vis curing to form a security feature. As used herein, the term "UV-Vis curing" refers to radiation curing of the ink layer 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 to 600 nm, and more preferably 200 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, that then initiate polymerization of the compound to form a cured binder. Radically curable monomers and oligomers are cured by a free-radical mechanism consisting of activation by UV-Vis light of one or more photoinitiators, which liberate free radicals that start the polymerization process. Optionally, one or more photosensitizers may be present. The photosensitizer is activated by one or more wavelengths emitted by a UV-Vis light source to reach an excited state. The excited photosensitizer transfers energy to one or more photoinitiators (in the case of free radical polymerization) or electrons (in the case of cationic polymerization), both of which then initiate the polymerization process.

[0044] Preferably, step c) comprises exposing the ink layer obtained in step b) to UV-Vis light emitted by a UV-Vis light source selected from the group consisting of a mercury lamp, preferably a medium-pressure mercury lamp, a UV-LED lamp, and sequences thereof. As demonstrated, for example, by Experiments E29a and E29b, for certain UV-Vis radiation-curable inks described herein (e.g., inks containing a diaryliodonium photoinitiator and a thioxanthone-based photosensitizer), the UV-Vis light source, i.e., a UV-LED lamp or a mercury lamp, used in step c) does not affect the optical properties exhibited by the security features produced via the manufacturing methods described and claimed herein. A typical sequence includes, in a first step, partially curing the UV-Vis emissive composition using one or more UV-LED lamps, and in a second step, using one or more medium-pressure mercury lamps. Mercury lamps advantageously emit light over a broad wavelength range in the UV-A, UV-B, and UV-C ranges. Therefore, there is a wide selection of photoinitiators or photoinitiator / photosensitizer combinations with absorption spectra that match at least one of the emission bands of mercury lamps. UV-LEDs have a more limited wavelength range, so that 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 a much less demanding heat dissipation system), are less prone to ozone formation, and have a longer lifespan.

[0045] The UV-Vis ray curable ink used in the manufacturing method according to the present invention is i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii) about 40% to about 75% by weight of either a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more UV-Vis radiation curable compounds other than a cycloaliphatic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii) and vi) are based on the total weight of the UV-Vis radiation curable ink.

[0046] Preferably, the UV-Vis radiation curable ink is a UV-Vis radiation curable screen printing ink, a UV-Vis radiation curable rotogravure ink, or a UV-Vis radiation curable flexographic printing ink, more preferably a UV-Vis radiation curable screen printing ink. The UV-Vis radiation curable ink used in the manufacturing method claimed herein has a viscosity of about 50 mPas to about 2000 mPas at 25°C, as measured using a Brookfield viscometer (DV-I Prime model) equipped with a 100 rpm spindle S27, or with a 50 rpm spindle S21 for measuring viscosities of 500 to 2000 mPas, and a 100 rpm spindle S21 for measuring viscosities of 500 mPas or less. The UV-Vis radiation curable screen printing ink used in the manufacturing method of the present invention claimed in this application has a viscosity of about 50 mPas to about 1000 mPas at 25°C, preferably about 100 mPas to about 1000 mPas at 25°C.

[0047] The silver nanoplatelets detected by UV-Vis may be in the form of a disk, a regular hexagon, a triangle, particularly an equilateral triangle, a trapezoid, particularly an isosceles trapezoid, or a mixture thereof. The silver nanoplatelets are preferably in the form of a disk, a trapezoid, a hexagon, or a mixture thereof.

[0048] The average diameter of the silver nanoplatelets is 50-150 nm, preferably 60-140 nm, and more preferably 70-120 nm, with a standard deviation of less than 60%, preferably less than 50%. The diameter of a silver nanoplatelet is the longest dimension of the silver nanoplatelet and corresponds to the largest dimension of the silver nanoplatelet when oriented parallel to the plane of a transmission electron spectroscopy (TEM) image. As used herein, the term "average diameter of silver nanoplatelets" refers to the average diameter determined by transmission electron microscopy (TEM) using Fiji image analysis software based on measurements of at least 300 randomly selected silver nanoplatelets, where the diameter of a silver nanoplatelet is the largest dimension of the silver nanoplatelet oriented parallel to the plane of the TEM image. TEM analysis was performed on a dispersion containing 24.1 wt. % silver nanoplatelets in isopropanol using a ZEISS EM910 instrument in bright-field mode at an electron beam accelerating voltage of 100 kV.

[0049] The average thickness of the silver nanoplatelets is in the range of 5-30 nm, preferably 7-25 nm, and more preferably 8-25 nm, with a standard deviation of less than 50%, preferably less than 30%. The thickness of the silver nanoplatelets is the shortest dimension of the silver nanoplatelets and corresponds to the largest dimension of the silver nanoplatelets when oriented perpendicular to the plane of a transmission electron microscope (TEM) image. As used herein, the term "average thickness of silver nanoplatelets" refers to the average thickness determined by transmission electron microscope (TEM) based on manual measurements of at least 50 randomly selected silver nanoplatelets oriented perpendicular to the plane of the TEM image, where the thickness of the silver nanoplatelets is the largest dimension of the silver nanoplatelets when oriented perpendicular to the plane of the TEM image. TEM analysis was performed on a dispersion containing 24.1 wt. % silver nanoplatelets in isopropanol using a ZEISS EM910 instrument in bright-field mode at an electron beam accelerating voltage of 100 kV.

[0050] The average aspect ratio of the silver nanoplatelets (defined as the ratio of the average diameter to the average thickness) is greater than 2.0, preferably greater than 2.2, and more preferably greater than 2.5.

[0051] Preferably, the average diameter of the silver nanoplatelets is in the range of 70-120 nm with a standard deviation of less than 50%, the average thickness of the silver nanoplatelets is in the range of 8-25 nm with a standard deviation of less than 30%, and the average aspect ratio of the silver nanoplatelets is greater than 2.5.

[0052] The silver nanoplatelets used in the UV-Vis radiation curable inks described herein are characterized by a highest wavelength absorption maximum between 560 and 800 nm, preferably between 580 and 800 nm, and most preferably between 600 and 800 nm. The highest wavelength absorption maximum is approximately 5 x 10 using a Varian Cary 50 UV-Vis spectrophotometer. -5The measurements were carried out in water at a silver concentration of 1000 M (mol / L). The absorption maxima have full width at half maximum (FWHM) values ​​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 5000L / (cm*mol Ag ), especially higher than 6000L / (cm*mol Ag ) higher.

[0053] To prevent aggregation and settling of the silver nanoplatelets upon storage, the silver nanoplatelets preferably have one or more surface stabilizers.

[0054] A preferred embodiment according to the present invention is a method for producing a security mechanism for protecting a valuable document as claimed in the present application and described herein, wherein silver nanoplatelets are provided on their surface with a compound of general formula (I): [ka] [In the formula, [ka] indicates binding to silver, R 1 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. The present invention relates to a method of forming a film having a surface stabilizer of the formula:

[0055] Preferably, Y is O. Also preferably, k4 is 0.

[0056] The surface stabilizer of general formula (I) preferably has an average molecular weight (Mn) of 1,000 to 20,000 [g / mol], more preferably 1,000 to 10,000 [g / mol], and most preferably 1,000 to 6,000 [g / mol].

[0057] If the stabilizer of formula (I) comprises, for example, ethylene oxide units (EO) and propylene oxide units (PO), the order of (EO) and (PO) may be fixed (block copolymer) or not (random copolymer).

[0058] Preferably, R 1 is H or C1~C 18 alkyl, and 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.

[0059] More preferably, R 1 is H or C1-C4 alkyl, and R 2 , R 3 , R 4 , R 5 , R 6 and R 7are each independently H or CH3, k1 is an integer ranging from 22 to 450, k2 and k3 are each independently 0 or an integer ranging from 1 to 100, k4 is 0, and k5 is an integer ranging from 1 to 4.

[0060] The most preferred surface stabilizers of general formula (I) are those of general formula (Ia): [ka] [In the formula, R 1 is H or a C1-C8 alkyl group, in particular H or C3, k1 is an integer ranging from 22 to 450, particularly from 22 to 150. It has.

[0061] Preferred surface stabilizers have an average molecular weight (M n MPEG thiol (poly(ethylene glycol) methyl ether thiol), such as MPEG 2000 thiol, MPEG 3000 thiol, MPEG 4000 thiol, MPEG 5000 thiol, and MPEG 6000 thiol, having an average molecular weight (M) of 2000 to 6000. n PEG thiol (O-(2-mercaptoethyl)-poly(ethylene glycol)) having a hydroxyl group, such as PEG2000 thiol, PEG3000 thiol, PEG4000 thiol, PEG5000 thiol, and PEG6000 thiol.

[0062] In another preferred embodiment of the present invention, the silver nanoplatelets contained in the UV-Vis radiation curable ink have a surface stabilizer which is a polymer or copolymer as described in WO200674969, which polymer or copolymer is prepared by the following steps: d1) In the first step, the structural element [ka] wherein X represents a group having at least one carbon atom, and the free radical X derived from X is capable of initiating polymerization. polymerizing one or more ethylenically unsaturated monomers in the presence of at least one nitroxyl ether having the formula: d2) 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 d1) or d2) is a C1-C6 alkyl or hydroxy C1-C6 alkyl ester of acrylic or methacrylic acid; and optionally e) A second step comprising the modification of the polymer or copolymer prepared in d1) or d2) by transesterification, amidation, hydrolysis or anhydride modification or a combination thereof. The compound is obtained by a method comprising:

[0063] The monomer in step d1) or d2) is preferably 4-vinyl-pyridine or pyridinium-ion, 2-vinylpyridine or pyridinium-ion, 1-vinyl-imidazole or imidazolinium-ion, or Formula CH2=C(R a )-(C=Z)-R b [In the formula, R a is hydrogen or methyl, R b is 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 18Alkylamino, 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 During the ceremony, An - is the anion of a monovalent organic or inorganic acid, y is an integer from 2 to 10, R 15 is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms; R 16 is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms; Me + is a monovalent metal atom or an ammonium ion, Z is oxygen or sulfur. The compound is selected from the group consisting of:

[0064] The second step e) is preferably a transesterification reaction. In step e), the alcohol is preferably of formula (A) R A -[O-CH2-CH2-] n -OH (A) [In the formula, R A is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl having up to 24 carbon atoms, and n is 1 to 150. It is an ethoxylate of

[0065] Preferably, step d1) or d2) 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 wt. % of C1-C6 alkyl esters of acrylic acid or methacrylic acid, based on the total weight of the monomers, and in the second or first radical polymerization step, respectively, the ethylenically unsaturated monomer or monomer mixture contains at least one monomer that does not have a primary or secondary ester bond.

[0066] In the first polymerization step, the monomer or monomer mixture contains 50 to 100% by weight of a C1 to C6 alkyl ester of acrylic acid or methacrylic acid (first monomer) based on the total weight of the monomers, and in the second polymerization step, the ethylenically unsaturated monomer or monomer mixture contains 4-vinyl-pyridine or a pyridinium ion, 2-vinyl-pyridine or a pyridinium ion, vinyl-imidazole or an imidazolinium ion, 3-dimethylaminoethyl acrylamide, 3-dimethylaminoethyl methacrylamide or a corresponding ammonium ion, 3-dimethylaminopropyl acrylamide or a corresponding ammonium ion, or 3-dimethylaminopropyl methacrylamide or a corresponding ammonium ion (second monomer).

[0067] The nitroxy alkyl ether preferably has the formula (O1) [ka] is a compound of

[0068] The surface stabilizer is preferably prepared by the following steps: d1) in a first step, 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-dimethylaminoethyl acrylamide, 3-dimethylaminoethyl methacrylamide, 3-dimethylaminopropyl acrylamide, and 3-dimethylaminopropyl methacrylamide, Structural Elements [ka] and polymerizing in the presence of at least one nitroxyl ether having the formula: e) modification of the polymer or copolymer prepared in d1) by transesterification, wherein the alcohol of step e) is of the formula R A -[O-CH2-CH2-] n1 -OH (A) [In the formula, R A is a saturated or unsaturated, straight or branched alkyl having 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl having up to 24 carbon atoms, and n1 is 1 to 150. The second step is the ethoxylate of The copolymer is obtained by a process comprising:

[0069] Preferably, the surface stabilizer obtained by the processes described herein has formula (III): [ka] [In the formula, R 11 and R 12 is H or methyl, R 13 , R a and R a’are each independently H or methyl, R b is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms; R b’ is R A -[O-CH2-CH2-] n1 -O-, R 14 teeth, [ka] and During the ceremony, An - is the anion of a monovalent organic or inorganic acid, y is an integer from 2 to 10, R 15 is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms; R 16 is a saturated or unsaturated, straight or branched chain alkyl having 1 to 22 carbon atoms; R A is a saturated or unsaturated, linear or branched alkyl having 1 to 22 carbon atoms, or an alkylaryl or dialkylaryl having up to 24 carbon atoms, and n1 is 1 to 150; m, n, and p are each independently an integer of 1 to 200; o is an integer between 1 and 150. It is a copolymer of

[0070] More preferably, the surface stabilizer has formula (III): [ka] [In the formula, R 11 and R 12 is H or methyl, m, n, and p are each independently an integer of 1 to 200; o is an integer between 1 and 150. The order of the monomers with indices m and n may be fixed (block copolymer) or not (random copolymer).

[0071] Examples of preferred copolymers to be used as stabilizers are the copolymers described in Examples A3 and A6 of WO200674969.

[0072] To improve the stability of the optical properties of the silver nanoplatelets upon storage or thermal exposure, the UV-Vis radiation curable ink may further comprise a stabilizer, such as a compound of general formula (IIa), (IIb), or (IIc).

[0073] The stabilizer has the formula R 20 -X(IIa), wherein R 20 is a straight or branched chain C1-C 25 Alkyl group or C2-C 25 Alkenyl group, -OH, -SH, -NH2, or -COOR 19 and wherein R 19 is a hydrogen atom or C1-C 25 is an alkyl group, and X is -OH, -SH, -NH2, or -COOR 19’ where R 19’ are hydrogen atoms, C1 to C 25 An alkyl or alkenyl group, -OH, -SH, -NH2, or -COOR 19’’ and wherein R 19’’ is a hydrogen atom or C1-C 25 It is an alkyl group.

[0074] Examples of compounds of formula (IIa) are 1-methylamine, 1-dodecylamine, 1-hexadecylamine, citric acid, oleic acid, D-cysteine, 1-dodecanethiol, 9-mercapto-1-nonanol, 1-thioglycerol, 11-amino-1-undecanethiol, cysteamine, 3-mercaptopropanoic acid, 8-mercaptooctanoic acid and 1,2-ethanedithiol.

[0075] The stabilizer may be a compound of formula (IIb) [ka] [In the formula, R 21a is a hydrogen atom, a halogen atom, a C1-C8 alkoxy group, or a C1-C8 alkyl group, R 21b is a hydrogen atom or a group of formula -CHR 24 -N(R 22 )(R 23 ) group, R 22 and R 23 are each independently a C1-C8 alkyl, a hydroxy C1-C8 alkyl group, or a group of the formula -[(CH2CH2)-O] n2 -CHCH-OH group, where n2 is 1 to 5, and R 24 is H or C1-C8 alkyl] It may also be a compound of the formula:

[0076] Examples of compounds of formula (IIb) include: [ka] These include, but are not limited to:

[0077] The stabilizer may be a "polyhydric phenol," i.e., a compound containing an optionally substituted benzene ring and at least two hydroxy groups attached thereto. The term "polyhydric phenol" includes polyphenols, e.g., tannic acid, and polycyclic aromatic hydrocarbons consisting of condensed benzene rings, where at least one benzene ring has at least two hydroxy groups attached thereto, e.g., 1,2-dihydroxynaphthalene. The "polyhydric phenol" may be substituted. Suitable substituents are described below.

[0078] In a preferred embodiment, the polyhydric phenol stabilizer contained in the UV-Vis radiation curable inks described herein has the general formula (IIc): [ka] [In the formula, R 25 are the same or different in each occurrence and are hydrogen atoms, halogen atoms, C1 to C 18 Alkyl groups, C1-C 18 Alkoxy group, or -C(=O)-R 26 It is the basis, R 26 is a hydrogen atom, a hydroxyl group, C1-C 18 an alkyl group, an unsubstituted or substituted amino group, an unsubstituted or substituted phenyl group, or a C1-C 18 is an alkoxy group, n3 is an integer from 1 to 4, m3 is an integer between 2 and 4, The sum of the integers m3 and n3 is 6. It is a polyhydric phenol.

[0079] In a more preferred embodiment, the polyhydric phenol stabilizer contained in the UV-Vis radiation curable inks described herein has the general formula (IIc'): [ka] [In the formula, R25a and R 25b are each independently a hydrogen atom, C1 to C 18 Alkyl groups, C1-C 18 Alkoxy groups, or groups of the formula -C(=O)-R 26 is the basis of R 26 is a hydrogen atom, a hydroxyl group, C1-C 18 an alkyl group, an unsubstituted or substituted amino group, an unsubstituted or substituted phenyl group, or a C1-C 18 is an alkoxy group, m3 is an integer between 2 and 4, especially an integer between 2 and 3. The polyhydric phenol represented by general formula (IIc') having two hydroxy groups at the ortho positions is particularly preferred.

[0080] In a further preferred embodiment, the polyhydric phenol stabilizer contained in the UV-Vis ray curable ink is a compound represented by the general formula (IIc″): [ka] It is a polyhydric phenol. [In the formula, R 25 is a hydrogen atom, formula -C(=O)-R 26 where R 26 are hydrogen atoms, C1 to C 18 Alkyl group or C1-C 18 Alkoxy groups, unsubstituted or substituted amino groups, especially C1-C 18 It is an alkyl group or a C1 to C8 alkoxy group.

[0081] General formula (IIc''') [ka] [In the formula, R 26 are hydrogen atoms, C1 to C 18 Alkyl group or C1-C 18 an alkoxy group, particularly a C1-C8 alkoxy group] Particularly preferred as stabilizers are polyhydric phenols of the formula (IIc'''): [ka] These include, but are not limited to:

[0082] Further stabilizers include those of the formula: [ka] [In the formula, R 25 are hydrogen atoms, C1 to C 18 Alkyl group, or group of formula -C(=O)-R 26 where R 26 is a hydrogen atom, a hydroxyl group, C1-C 18 Alkyl group or C1-C 18 Alkoxy groups, unsubstituted or substituted amino groups, unsubstituted or substituted phenyl groups, especially C1-C 18 alkyl group or C1-C8 alkoxy group] Examples of polyhydric phenols include compounds having one of the following structures: [ka] Includes:

[0083] In a particularly preferred embodiment, the stabilizer is selected from compounds of formula (IIb), (IIc) and mixtures thereof.

[0084] A preferred embodiment according to the present invention relates to a method for making the security feature described and claimed herein, wherein the silver nanoplatelets have one or more surface stabilizers according to the general formula (I) and one or more surface stabilizers according to the general formula (III), and the UV-Vis radiation curable ink comprises one or more stabilizers according to the general formula (IIb):

[0085] The dispersion of silver nanoplatelets used in the preparation of the UV-Vis radiation curable ink used in the manufacturing method according to the present invention can be obtained using the following method. (A) a silver precursor and a compound represented by formula (I') [ka] [In the formula, R 1 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. and a compound of Follow these steps: D1) In the first step, the structural element [ka] wherein X represents a group having at least one carbon atom, and the free radical X derived from X is capable of initiating polymerization. polymerizing one or more ethylenically unsaturated monomers in the presence of at least one nitroxyl ether having the formula: D2) In the first step, at least one stable free nitroxyl radical is generated. [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 D1) or D2) is a C1-C6 alkyl or hydroxy C1-C6 alkyl ester of acrylic or methacrylic acid; and optionally E) A second step comprising the modification of the polymer or copolymer prepared in D1) or D2) by transesterification, amidation, hydrolysis or anhydride modification or a combination thereof. a polymer or copolymer obtainable by a process comprising the steps of: Water and optionally an antifoaming agent preparing a solution comprising: (B1) preparing a solution containing a reducing agent containing at least one boron atom in the molecule and water; (B2) adding the solution obtained in step (A) to the solution obtained in step (B1) and adding one or more complexing agents; (C) adding a hydrogen peroxide solution in water; and (D) optionally adding a stabilizer to the mixture obtained in step (C).

[0086] Silver precursors include AgNO3; AgClO4; Ag2SO4; AgCl; AgF; AgOH; Ag2O; AgBF4; AgIO3; AgPF6; R 200 CO2Ag, R 200 SO3Ag [In the formula, R 200 is unsubstituted or substituted C1 to 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 18silver(I) compounds selected from the group consisting of silver nitrate, silver acetate, silver perchlorate, silver methanesulfonate, silver benzenesulfonate, silver toluenesulfonate, silver trifluoromethanesulfonate, silver sulfate, silver fluoride, and mixtures thereof, and more preferably silver nitrate.

[0087] 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, allyloxyboranes such as catecholborane, amine borane complexes such as diethylanilineborane, tert-butylamineborane, morpholineborane, dimethylamineborane, triethylamineborane, pyridineborane, ammoniaborane, and mixtures thereof. Sodium borohydride is most preferred.

[0088] The one or more complexing agents are selected from the group consisting 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.

[0089] Non-limiting examples of complexing agents include ammonia, methylamine, dimethylamine, ethylamine, ethylenediamine, diethylenetriamine, ethylenediaminetetraacetic acid (EDTA), ethylenediamine N,N'-disuccinic acid (EDDS), methylglycine diacetic acid (MGDA), diethylenetriaminepentaacetic acid (DTPA), propylenediaminetetracetic 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 (NaMGDA) and the tetrasodium salt of EDTA.

[0090] Antifoaming agents are compounds or compositions capable of suppressing foam formation in the reaction mixture, such as 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, and N, Sigma Antifoam SE-15, and Struktol SB-2080. The amount of antifoaming agent is in the range of 0.00001% to 5% by weight, preferably 0.0001% to 3% by weight, and more preferably 0.001% to 2% by weight, based on the total weight of the reaction mixture before the addition of hydrogen peroxide.

[0091] An antifoaming agent may be added to the solution prepared in step (a) and / or the solution prepared in step (B).

[0092] The reaction to form silver nanoplatelets is carried out by gradually adding the silver precursor solution to the reducing agent solution. The temperatures of both solutions range from -3°C to 40°C, and the gradual addition is completed within 15 minutes to 24 hours.

[0093] The silver nanoplatelets may be further subjected to further purification and / or isolation methods, such as decantation, (ultra)filtration, (ultra)centrifugation, reversible or irreversible aggregation, phase inversion with organic solvents, and combinations thereof. The dispersion of silver nanoplatelets may 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.

[0094] The silver nanoplatelets used herein are described in WO2020224982.

[0095] A preferred embodiment of the present invention relates to a method for producing the security features described and claimed herein, wherein the UV-Vis radiation curable ink comprises silver nanoplatelets at a concentration of about 5% to about 20% by weight, preferably about 7.5% to about 17.5% by weight, more preferably about 10% to about 15% by weight, e.g., about 12.5% ​​by weight, based on the total weight of the UV-Vis radiation curable ink. The concentration of silver nanoplatelets in the UV-Vis radiation curable ink used in the method according to the present invention is significantly lower than the concentration of silver platelets used in prior art inks. Thus, the claimed manufacturing method allows for the cost-effective production of dichroic security features with optical effects similar to those of the prior art, but with significantly improved mechanical resistance properties.

[0096] In one embodiment according to the present invention, the UV-Vis radiation curable ink used in the manufacturing method described and claimed herein is a cationically curable ink (i.e. an ink containing exclusively cationically curable monomers and no radically curable monomers), i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-1) about 40% by weight to about 75% by weight of an alicyclic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-1) and vi) are based on the total weight of the UV-Vis radiation curable ink.

[0097] In an alternative embodiment according to the present invention, the UV-Vis radiation curable ink comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-5) about 40% by weight to about 75% by weight of a mixture of an alicyclic epoxide and one or more UV-Vis ray curable compounds other than an alicyclic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-5) and vi) are based on the total weight of the UV-Vis radiation curable ink. The one or more UV-Vis radiation curable compounds other than cycloaliphatic epoxides may include vii) one or more cationically curable monomers other than cycloaliphatic epoxides, and / or viii) one or more radically curable monomers and / or oligomers. When the one or more UV-Vis radiation curable compounds other than cycloaliphatic epoxides include viii) one or more radically curable monomers and / or oligomers, the UV-Vis radiation curable ink further includes ix) one or more free-radical photoinitiators. Preferably, when the one or more UV-Vis radiation curable compounds other than cycloaliphatic epoxides include vii) one or more cationically curable monomers other than cycloaliphatic epoxides, the ratio of the weight percent (wt%) of the cycloaliphatic epoxides present in the ink to the weight percent (wt%) of the one or more cationically curable monomers other than cycloaliphatic epoxides present in the ink is greater than about 1.1: 1. Also preferably, when the one or more UV-Vis radiation curable compounds other than cycloaliphatic epoxides include viii) one or more radically curable monomers and / or oligomers, the ratio of the weight percent (wt%) of the one or more radically curable monomers and / or oligomers present in the ink to the sum of the cationically curable monomers, including cycloaliphatic epoxides, present in the ink is less than about 1.6: 1, preferably less than about 1.53: 1, the weight percent (wt%) being based on the total weight of the ink.

[0098] Thus, in a preferred embodiment according to the present invention, the UV-Vis radiation curable ink used in the manufacturing method described and claimed herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-2) about 40% by weight to about 75% by weight of a mixture of an alicyclic epoxide and one or more cationically curable monomers other than the alicyclic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-2) and vi) are based on the total weight of the UV-Vis radiation curable ink. Preferably, the ratio of the weight percentage (wt%) of the cycloaliphatic epoxide present in the ink to the weight percentage (wt%) of one or more cationically curable monomers other than the cycloaliphatic epoxide present in the ink is greater than about 1.1:1, where the weight percentages (wt%) are based on the total weight of the ink. More preferably, the cycloaliphatic epoxide present in the cationically curable ink is in an amount of about 20 wt% to about 70 wt%, based on the total weight of the ink, and the one or more cationically curable monomers other than the cycloaliphatic epoxide present in the cationically curable ink is in an amount of about 5 wt% to about 20 wt%, based on the total weight of the UV-Vis radiation curable ink, provided that the weight percentage (wt%) of the cycloaliphatic epoxide present in the ink to the one or more cationically curable monomers other than the cycloaliphatic epoxide present in the ink is greater than about 1.1:1.

[0099] In a further alternative preferred embodiment according to the present invention, the UV-Vis radiation curable ink comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-3) about 40% by weight to about 75% by weight of a mixture of an alicyclic epoxide and one or more radically curable monomers and / or oligomers; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; ix) one or more free radical photoinitiators, and optionally vi) up to 25% by weight of an organic solvent; Including, The weight percentages of ii-3) and vi) are based on the total weight of the UV-Vis radiation curable ink, the hybrid ink (i.e., an ink containing both cationically curable and radically curable monomers). Preferably, the ratio of the weight percentage (wt%) of one or more radically curable monomers and / or oligomers present in the hybrid ink to the weight percentage (wt%) of the cycloaliphatic epoxide present in the hybrid ink is less than about 1.6:1, more preferably less than about 1.53:1, where the weight percentages (wt%) are based on the total weight of the ink. In a more preferred embodiment, the hybrid ink comprises from about 25% to about 65% by weight of a cycloaliphatic epoxide and from about 10% to about 40% by weight of one or more radically curable monomers and / or oligomers, with the proviso that the ratio of the weight percent (wt%) of the one or more radically curable monomers and / or oligomers present in the hybrid ink to the weight percent (wt%) of the cycloaliphatic epoxide present in the hybrid ink is less than about 1.6:1, more preferably less than about 1.53:1, and wherein the weight percent (wt%) is based on the total weight of said curable ink.

[0100] In an alternative preferred embodiment, the UV-Vis radiation curable ink used in the manufacturing method described and claimed herein comprises: i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii-4) about 40% by weight to about 75% by weight of a mixture of an alicyclic epoxide, one or more cationically curable monomers other than the alicyclic epoxide, and one or more radically curable monomers and / or oligomers; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; ix) one or more free radical photoinitiators, and optionally vi) up to 25% by weight of an organic solvent; wherein the weight percentages of ii-4) and vi) are based on the total weight of the UV-Vis radiation curable ink, and are hybrid inks (i.e., inks containing both cationically curable and radically curable monomers). Preferably, the ratio of the weight percent (wt%) of one or more radically curable monomers and / or oligomers present in the UV-Vis ray hybrid curable ink to the sum of the weight percent (wt%) of alicyclic epoxide present in the UV-Vis ray hybrid curable ink and the weight percent (wt%) of one or more cationically curable monomers other than alicyclic epoxides present in the UV-Vis ray hybrid curable ink is less than about 1.6:1, more preferably less than about 1.53:1, and the ratio of the weight percent (wt%) of alicyclic epoxide present in the UV-Vis ray hybrid curable ink to the weight percent (wt%) of one or more cationically curable monomers other than alicyclic epoxides present in the UV-Vis ray hybrid curable ink is greater than about 1.1:1, where the weight percents (wt%) are based on the total weight of the curable ink. In a more preferred embodiment, the hybrid ink comprises from about 10% to about 65% by weight of a cycloaliphatic epoxide, from 5% to about 20% by weight of one or more cationically curable monomers other than cycloaliphatic epoxides, and from about 10% to about 40% by weight of one or more radically curable monomers and / or oligomers, wherein the ratio of the weight percent (wt%) of the one or more radically curable monomers and / or oligomers present in the ink to the weight percent (wt%) of the one or more cationically curable monomers other than cycloaliphatic epoxides present in the ink is less than about 1.6:1, more preferably less than about 1.53:1, and wherein the ratio of the weight percent (wt%) of the cycloaliphatic epoxide present in the ink to the weight percent (wt%) of the one or more cationically curable monomers other than cycloaliphatic epoxides present in the ink is greater than about 1.1:1, the weight percents (wt%) being based on the total weight of the ink.

[0101] Experiments E15 to E19 according to the present invention demonstrate that similar optical properties can be obtained with the UV-Vis radiation hybrid curable inks described herein (i.e., inks containing both cationically curable and radically curable monomers) and cationically curable inks (i.e., inks containing exclusively cationically curable monomers and no radically curable monomers).

[0102] Advantageously, the methods claimed and described herein that rely on the use of the UV-Vis radiation cationically curable inks described herein or the use of the UV-Vis radiation hybrid curable inks described herein provide security features with improved mechanical properties compared to similar security features known in the art that are obtained from UV radically curable inks or solvent-based inks, particularly UV radically curable inks or solvent-based inks containing high concentrations of silver nanoplatelets.

[0103] The UV-Vis radiation curable inks described herein contain cycloaliphatic epoxides, which are cationically curable monomers, as known to those skilled in the art. The cycloaliphatic epoxides described herein may be difunctional or polyfunctional. Preferably, the cycloaliphatic epoxides described herein contain at least one cyclohexane group and at least two epoxide groups. Preferably, the cycloaliphatic epoxides have the general formula (IV): [ka] [wherein -L- represents a single bond or a divalent group containing one or more atoms] The alicyclic epoxide of general formula (IV) may be optionally substituted with one or more straight-chain or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl).

[0104] In general formula (IV), the divalent group -L- may be a straight-chain or branched-chain alkylene group containing 1 to 18 carbon atoms. Examples of the straight-chain or branched-chain alkylene group include, but are not limited to, methylene, methylmethylene, dimethylmethylene, ethylene, propylene, and trimethylene groups.

[0105] In general formula (IV), the divalent group -L- may be a divalent alicyclic hydrocarbon group or a cycloalkylidene group, such as a 1,2-cyclopentylene group, a 1,3-cyclopentylene group, a cyclopentylidene group, a 1,2-cyclohexylene group, a 1,3-cyclohexylene group, a 1,4-cyclohexylene group, and a cyclohexylidene group.

[0106] In general formula (IV), -L- may be a divalent group comprising one or more oxygen-containing linking groups, said oxygen-containing linking groups being selected from -C(=O)-, -OC(=O)O-, -C(=O)O-, and -O-. Preferably, the cycloaliphatic epoxide is of general formula (IV), wherein -L- is a divalent group comprising 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 cycloaliphatic epoxides of general formula (IV-a), (IV-b), or (IV-c) as defined below. [ka] [In the formula, L 1 may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); L 2may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); l1 and l2 are, independently of each other, integers from 0 to 9, preferably integers from 0 to 3. [ka] [In the formula, L 1 may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 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 straight-chain or branched-chain alkyl radicals 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 straight-chain or branched-chain alkyl radicals containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); l1 and l2 are, independently of one another, integers from 0 to 9, preferably from 0 to 3; -L 3- is a single bond or a straight or branched chain divalent hydrocarbon radical containing 1 to 10 carbon atoms, preferably 3 to 8 carbon atoms, such as an alkylene radical, e.g., trimethylene, tetramethylene, hexamethylene, and 2-ethylhexylene, and a cycloalkylene radical, e.g., 1,2-cyclohexylene, 1,3-cyclohexylene, 1,4-cyclohexylene, cyclohexylidene. [ka] [In the formula, L 1 may be the same or different at each occurrence and are straight- or branched-chain alkyl radicals containing 1 to 3 carbon atoms, e.g., methyl, ethyl, n-propyl, and i-propyl; L 2 may be the same or different at each occurrence and are straight- or branched-chain alkyl radicals containing 1 to 3 carbon atoms, e.g., methyl, ethyl, n-propyl, and i-propyl; l1 and l2 are, independently of each other, integers from 0 to 9, preferably integers from 0 to 3.

[0107] Preferred cycloaliphatic epoxides of general formula (IV-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.

[0108] Preferred cycloaliphatic epoxides of general formula (IV-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.

[0109] A preferred cycloaliphatic epoxide of general formula (IV-c) is 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-meta-dioxane.

[0110] Further, alicyclic epoxides include alicyclic epoxides of general formula (V) and alicyclic epoxides of general formula (VI), which may be substituted with one or more linear or branched alkyl groups containing 1 to 10 carbon atoms (methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, hexyl, octyl, and decyl), preferably one or more linear or branched alkyl groups containing 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl). [ka]

[0111] The cycloaliphatic epoxides described herein may be hydroxy- or (meth)acrylate-modified, such as those sold by Daicel under the trade names Cyclomer A400 (CAS: 64630-63-3) and Cyclomer M100 (CAS number: 82428-30-6), or those sold by TetraChem / Jiangsu under the trade names TTA15 and TTA16.

[0112] The UV-Vis radiation curable inks described herein contain one or more cationic photoinitiators. Preferably, the concentration of the one or more cationic photoinitiators in the UV-Vis radiation cationically curable inks described herein (i.e., inks containing exclusively cationically curable monomers and no radically curable monomers) is from about 1 wt % to about 10 wt %, preferably from about 1.1 wt % to about 8 wt %, and more preferably from about 1.1 wt % to about 6 wt %, based on the total weight of the UV-Vis radiation cationically curable ink. Preferably, the concentration of the one or more cationic photoinitiators in the UV-Vis radiation hybrid curable inks described herein (i.e., inks containing both cationically curable and radically curable monomers) is from 1 wt % to about 6 wt %, based on the total weight of the UV-Vis radiation cationically curable ink.

[0113] The one or more cationic photoinitiators (also referred to in the art as photoacid generators) used in the UV-Vis radiation curable inks described herein are preferably onium salts selected from the group consisting of azonium salts, oxonium salts, iodonium salts, sulfonium salts, and mixtures thereof, more preferably onium salts selected from the group consisting of oxonium salts, iodonium salts, sulfonium salts, and mixtures thereof, and even more preferably onium salts selected from the group consisting of sulfonium salts, iodonium salts, and mixtures thereof.

[0114] The one or more iodonium salts described herein have a cationic portion and an anionic portion, where the anionic portion is preferably BF4 - , B(C6F5)4 - , PF6 - , AsF6 - , SbF6 - or CF3SO3 - , more preferably SbF6 -wherein the cationic moiety is preferably an aromatic iodonium ion, more preferably an iodonium ion containing two aryl groups, wherein the two aryl groups are 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, preferably one or more alkyl groups. Iodonium salts particularly suitable for the present invention are sold under the names DEUTERON UV 1240, DEUTERON UV 1242, DEUTERON UV 2257, DEUTERON UV 1250, and DEUTERON UV 3100, all by DEUTERON; OMNICAT 250, OMNICAT 440, and OMNICAT 445, all by IGM Resins; and SpeedCure 937, SpeedCure 938, and SpeedCure 939, all by Lambson.

[0115] The sulfonium salt(s) described herein have a cationic portion and an anionic portion, where the anionic portion is preferably BF4 - , B(C6F5)4 - , PF6 - , (PF 6-h (C j F 2j-1 ) h ) - (wherein h is an integer of 1 to 5, and j is an integer of 1 to 4), AsF6 - , SbF6 - , CF3SO3 - , perfluoroalkyl sulfonates or pentafluorohydroxyantimonates, more preferably SbF6 -wherein the cationic moiety is preferably an aromatic sulfonium ion, more preferably a sulfonium ion containing two or more aryl groups, wherein the two or more aryl groups are independently 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, but are not limited to, 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 sold under the names SpeedCure 976, SpeedCure 976D, and SpeedCure 992, all sold by Lambson, and ESACURE 1187, OMNICAT 270, OMNICAT 320, OMNICAT 432, and OMNICAT 550, all sold by IGM Resins.

[0116] The one or more oxonium salts described herein have a cationic portion and an anionic portion, where the anionic portion is preferably BF4 - , B(C6F5)4 - , PF6 - , AsF6 - , SbF6 - or CF3SO3 - , more preferably BF4 -wherein the cationic moiety is preferably an aromatic oxyonium ion, more preferably a pyrylium ion preferably substituted with one or more aryl groups, wherein the one or more aryl groups may be 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 groups, one or more hydroxy groups, or a combination thereof. A particularly preferred oxonium salt for the present invention is 2,4,6-triphenylpyrylium tetrafluoroborate.

[0117] Other examples of useful 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 and K. Dietliker, edited by G. Bradley, co-published by John Wiley & Sons and SITA Technology Limited in 1998.

[0118] The one or more cationically curable monomers other than cycloaliphatic epoxides described herein are selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers such as epoxides, oxetanes and tetrahydrofuran, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl-containing compounds and mixtures thereof, preferably selected from the group consisting of vinyl ethers and cyclic ethers such as epoxides, oxetanes and tetrahydrofuran, more preferably selected from the group consisting of vinyl ethers. Preferably, the ratio of the weight percent (wt%) of cycloaliphatic epoxide present in the ink described herein to the weight percent (wt%) of the one or more cationically curable monomers other than cycloaliphatic epoxides present in said ink is greater than about 1.1:1, where the weight percent (wt%) is based on the total weight of the ink.

[0119] Vinyl ethers are known in the art to accelerate curing and reduce tack, thus limiting the risk of blocking and offset when printed sheets are placed in a stack immediately after printing and curing. Vinyl ethers also improve the physical and chemical resistance of the printed security element and enhance the flexibility and adhesion of the printed and cured ink layer to the substrate, which is particularly advantageous for printing on plastic and polymer substrates. Vinyl ethers also help reduce the viscosity of the ink while copolymerizing strongly with the ink vehicle.

[0120] Examples of preferred vinyl ethers include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, ethylhexyl vinyl ether, octadecyl vinyl ether, dodecyl vinyl ether, isopropyl vinyl ether, tert-butyl vinyl ether, tert-amyl vinyl ether, cyclohexyl vinyl ether, cyclohexanedimethanol monovinyl ether, cyclohexanedimethanol divinyl ether, 4-(vinyloxymethyl)cyclohexylmethylbenzoate, 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 methyl vinyl ether, triethylene glycol monobutyl vinyl ether, tetraethylene glycol divinyl ether, poly(tetrahydrofuran) divinyl ether, polyethylene glycol-520 methyl vinyl ether, pluriol-E200 divinyl ether, tris[4-(vinyloxy)butyl]trimellitate, 1,4-bis(2-vinyloxyethoxy)benzene, 2,Examples of suitable vinyl ethers include 2-bis(4-vinyloxyethoxyphenyl)propane, bis[4-(vinyloxy)methyl]cyclohexyl]methyl]terephthalate, and bis[4-(vinyloxy)methyl]cyclohexyl]methyl]isophthalate. Suitable vinyl ethers are sold by BASF under the names EVE, IBVE, DDVE, ODVE, BDDVE, DVE-2, DVE-3, CHVE, CHDM-di, and HBVE. One or more of the vinyl ethers described herein may be hydroxy- or (meth)acrylate-modified (e.g., Nippon Shokubai's VEEA, 2-(2-vinyloxyethoxy)ethyl acrylate (CAS: 86273-46-3)).

[0121] Oxetane compounds are known in the art to accelerate curing and reduce tack, thus limiting the risk of blocking and offset when printed sheets are placed in a stack immediately after printing and curing. Oxetane compounds also help reduce the viscosity of the ink while copolymerizing strongly with the ink vehicle.

[0122] Preferred examples of oxetane 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(p-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 (e.g., UVi-Cure S170 (CAS: 37674-57-0) from Lambson).

[0123] Preferred examples of epoxide compounds include butanediol diglycidyl ether, butyl glycidyl ether, hexadecyl glycidyl ether, 2-ethyl-hexyl glycidyl ether, octyl glycidyl ether, decyl glycidyl ether, dodecyl glycidyl ether, tetradecyl glycidyl ether, and mixtures thereof.

[0124] The one or more radically curable monomers described herein are selected from the group consisting of mono(meth)acrylates, di(meth)acrylates, tri(meth)acrylates, tetra(meth)acrylates, and mixtures thereof, preferably selected from the group consisting of tri(meth)acrylates, tetra(meth)acrylates, and mixtures thereof. The term "(meth)acrylate" in the context of the present invention refers to the acrylate and the corresponding methacrylate.

[0125] Preferred examples of mono(meth)acrylates include 2(2-ethoxyethoxy)ethyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, C 12 ~C 14 Alkyl (meth)acrylate, C 16 ~C 18Included are alkyl (meth)acrylates, caprolactone (meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, nonylphenol (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, octyldecyl (meth)acrylate, tridecyl (meth)acrylate, 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] The radically curable (meth)acrylate oligomer described herein is preferably selected from the group consisting of epoxy (meth)acrylates, (meth)acrylated oils, (meth)acrylated epoxidized oils, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, polyacrylic acid (meth)acrylates, polyacrylic acid ester (meth)acrylates, and mixtures thereof, and more preferably selected from the group consisting of epoxy (meth)acrylates, polyester (meth)acrylates, aliphatic or aromatic polyurethane (meth)acrylates, and mixtures thereof.

[0130] The radically curable oligomer described herein is preferably a (meth)acrylate oligomer, which may be branched or essentially linear, and the (meth)acrylate functional group(s) may each be a terminal group and / or a pendant side group attached to the oligomer backbone. Preferably, the radically curable oligomer is selected from the group consisting of (meth)acrylic oligomers, urethane (meth)acrylate oligomers, polyester (meth)acrylate oligomers, polyether (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof, more preferably polyester (meth)acrylate oligomers, epoxy (meth)acrylate oligomers, and mixtures thereof.

[0131] Suitable examples of epoxy (meth)acrylate oligomers include, but are not limited to, aliphatic epoxy (meth)acrylate oligomers, particularly mono(meth)acrylates, di(meth)acrylates, and tri(meth)acrylates, 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.

[0132] The one or more free radical photoinitiators are preferably selected from the group consisting of hydroxyketones (e.g., α-hydroxyketones), alkoxyketones (e.g., α-alkoxyketones), acetophenones, benzophenones, ketosulfones, benzil ketals, benzoin ethers, phosphine oxides, phenyl glyoxylates, thioxanthones, and mixtures thereof, more preferably selected from the group consisting of phosphine oxides, hydroxyketones, thioxanthones, and mixtures thereof. Preferably, the concentration of the one or more free radical photoinitiators in the UV-Vis radiation hybrid curable inks described herein is from about 1% to about 6% by weight, the percentages being based on the total weight of the UV-Vis radiation hybrid curable ink.

[0133] Suitable α-hydroxy ketones include, but are not limited to, (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, oligo[2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone].

[0134] Suitable acetophenones include, but are not limited to, 2,2-diethoxyacetophenone, 2-methoxy-2-phenylacetophenone.

[0135] Suitable benzophenones include, but are not limited to, 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.

[0136] Suitable ketosulfones include, but are not limited to, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one.

[0137] Suitable benzil ketals include, but are not limited to, 2,2-dimethoxy-2-phenylacetophenone.

[0138] Suitable benzoin ethers include, but are not limited to, 2-ethoxy-1,2-diphenylethane, 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.

[0139] Suitable phosphine oxides include, but are not limited to, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, substituted acylphosphine oxides, a mixture of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide and 2-hydroxy-2-methylpropiophenone, a mixture of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2-hydroxy-2-methylpropiophenone, a mixture of ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate and 2-hydroxy-2-methylpropiophenone, and a mixture of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate.

[0140] Suitable thioxanthones include, but are not limited to, 2-methylthioxanthone, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 1-chloro-4-propoxythioxanthone, and polymeric thioxanthone derivatives.

[0141] Suitable phenyl glyoxylates include, but are not limited to, methyl benzoyl formate, 2-[2-oxo-2-phenyl-acetoxy-ethoxy]ethyl 2-oxo-2-phenylacetate, and a mixture of 2-[2-oxo-2-phenyl-acetoxy-ethoxy]ethyl 2-oxo-2-phenylacetate and oxy-phenyl-acetic acid 2-[2-hydroxy-ethoxy]-ethyl ester.

[0142] 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 ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate.

[0143] The UV-Vis radiation curable inks described herein, specifically the UV-Vis radiation cationically curable inks described herein and the UV-Vis radiation hybrid curable inks described herein, comprise iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride. For example, as shown by Experiments E17-E20, E24-E27 according to the present invention and Comparative Experiment C8, the UV-Vis radiation curable ink must contain at least about 69% by weight of a polyvinyl chloride copolymer, the weight percentage being based on the total weight of the UV-Vis radiation curable ink, and via the manufacturing method claimed herein, provide a security feature that exhibits a metallic yellow color when viewed in incident light and a blue color when viewed in transmitted light. UV-Vis radiation curable inks (e.g., Ink I25) that do not contain a polyvinyl chloride copolymer exhibit a subdued color, such as brown or dark brown, and a low chroma value C when viewed in incident light. * , resulting in a security feature and, as a result, not suitable for use in the manufacturing method of the present invention claimed herein. It is within the common general knowledge of one skilled in the art of ink formulation to consider the weight percentages of the remaining components of the ink, particularly the weight percentage of the radically curable oligomer, if present, and the printing process in which the formulated ink will be printed, in order to select the appropriate weight percentage of the polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride. The concentration of the polyvinyl chloride copolymer in the UV-Vis radiation curable ink is preferably less than 15% by weight, more preferably between about 2.9% and 12% by weight, even more preferably between about 4.9% and 11.6% by weight, and most preferably between about 6% and 8.6% by weight, the weight percentages being based on the total weight of the UV-Vis radiation curable ink.

[0144] The polyvinyl chloride copolymer must contain at least about 69% by weight, and preferably at least about 75% by weight, vinyl chloride. A comparison of Experiment C7, which was conducted for purposes of comparison with Experiments E21-E23 in accordance with the present invention, demonstrates that in order to provide a security feature that exhibits a metallic yellow color when viewed in incident light via the methods of manufacture claimed herein, the polyvinyl chloride copolymer must contain at least about 69% by weight, and preferably at least about 75% by weight, vinyl chloride.

[0145] In a preferred embodiment, the polyvinyl chloride copolymer is selected from the group consisting of vinyl chloride-vinyl acetate copolymer and vinyl chloride-hydroxyacrylate copolymer, such as 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 3×10 as determined by size exclusion chromatography using polystyrene as a standard and tetrahydrofuran as a solvent. 4 g / mol ~ approx. 8×10 4 Particularly suitable examples of polyvinyl chloride copolymers for the present invention are those sold by Wacker under the names Vinnol® H14 / 36, Vinnol® E15 / 40A and Vinnol® E22 / 48A.

[0146] Surprisingly, it has been found that the use of perfluoropolyethers functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate as surfactants in the UV-Vis radiation curable inks described herein is essential for producing a security feature that exhibits a metallic yellow color when viewed in incident light. For example, as demonstrated by Experiments E7 and E8 in accordance with the present invention and Experiments C2-C5 performed for comparative purposes, only UV-Vis radiation curable inks containing perfluoropolyether surfactants functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate provide a security feature that exhibits a metallic yellow color when viewed in incident light. The security features fabricated as described in Experiments C2-C5, using UV-Vis radiation curable inks containing perfluoropolyether surfactants lacking functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate (e.g., Inks I4 and I5 containing perfluoropolyether-based anionic surfactants and perfluoropolyether-based nonionic surfactants, respectively), or fluorosurfactants lacking a perfluoropolyether backbone in addition to functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate (e.g., Inks I6 and I7 containing fluoroalkyl nonionic surfactants), exhibit a brown to dark brown color in reflection, a color that is not noticeable to the general public and is therefore not suitable for use in dichroic security features to protect valuable documents.

[0147] The perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate and methacrylate comprises a perfluoropolyether backbone and one or more, preferably two or more, terminal functional groups selected from the group consisting of hydroxyl, acrylate and methacrylate, and is characterized by an average molecular weight (Mn) of less than about 2000 [g / mol]. As used herein, the perfluoropolyether backbone represents the residue of a perfluoropolyether polymer containing randomly distributed repeating units selected from perfluoromethyleneoxy (-CF2O-) and perfluoroethyleneoxy (-CF2-CF2O-). The perfluoropolyether residue is directly linked to the terminal functional group, or is linked to the terminal functional group via a spacer selected from 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 fluorinated at the carbon atom that connects the spacer to the perfluoropolyether residue, a linear or branched hydrocarbon group containing one or more urethane groups, and optionally one or more cyclic moieties, including saturated cyclic moieties (for example, cyclohexylene) and aromatic cyclic moieties (for example, phenylene). In a preferred embodiment, the perfluoropolyether surfactant is functionalized with one or more hydroxyl functional groups.

[0148] In a further preferred embodiment, the perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate is a compound of general formula (VII) having an average molecular weight of about 1200 [g / mol] to about 2000 [g / mol]. [ka] [In the formula, f and e are integers independently selected from 1, 2 and 3; FG 1 and FG 2 are terminal functional groups independently selected from the group consisting of -OH, -OC(O)CH=CH2, and -OC(O)C(CH3)=CH2; -S 1 - is a single bond, or [ka] represents a spacer selected from During the ceremony, -J 1 -teeth, [ka] is selected from During the ceremony, j 1 is an integer from 1 to 12, preferably from 4 to 10, L 5 may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); L 6 may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); l 5 and l 6are, independently of one another, integers from 0 to 4, preferably from 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 from 1 to 6, preferably an integer from 1 to 3; b is an integer from 1 to 6, preferably from 2 to 4; -S 2 - is a single bond, or [ka] represents a spacer selected from During the ceremony, -J 4 -teeth, [ka] is selected from During the ceremony, j 4 is an integer from 1 to 12, preferably from 4 to 10, L 7 may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); L 8may be the same or different in each occurrence and are straight- or branched-chain alkyl radicals 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 1 to 3 carbon atoms (e.g., methyl, ethyl, n-propyl, and i-propyl); l 7 and l 8 are, independently of one another, integers from 0 to 4, preferably from 0 to 1, -J 6 - is selected from -O-, -CH2-, -CH(CH3)-, and -C(CH3)2-; -J 5 -teeth, [ka] is selected from wherein r is an integer from 1 to 6, preferably from 1 to 3; w is an integer from 1 to 6, preferably from 2 to 4; In the formula, s and t are integers selected so that the average molecular weight of the compound of general formula (VII) is about 1200 [g / mol] to about 2000 [g / mol].

[0149] Preferably, in the general formula (VII), FG 1 and FG 2 represent, independently of each other, -OC(O)CH=CH2 or -OC(O)C(CH3)=CH2, -S 1 -teeth, [ka] wherein b has the meaning defined herein; -S 2 -teeth, [ka] where w has the meaning defined herein.

[0150] Similarly, preferably, in the general formula (VII), FG 1 and FG 2 represents -OH, -S 1 - is a single bond or [ka] wherein a has the meaning defined herein; -S 2 - is a single bond or [ka] wherein r has the meaning defined herein; and the sum of o and r is a number from 3 to 9.

[0151] Particularly suitable examples of perfluoropolyether surfactants functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate for the present invention are those sold by Solvay under the names Fluorolink E10H, Fluorolink MD700, Fluorolink AD1700, and Fluorolink E series.

[0152] The concentration of the perfluoropolyether surfactant described herein in the UV-Vis radiation curable ink is preferably from about 0.05% to about 5% by weight, preferably from about 0.075% to about 5% by weight, and more preferably from about 0.1% to about 2.5% by weight, where the weight percentages are based on the total weight of the UV-Vis radiation curable ink. For example, as shown by Experiments E9-E14 in accordance with the present invention, concentrations of perfluoropolyether surfactant of from about 0.05% to about 2.5% by weight, preferably from about 0.075% to about 2.5% by weight, and more preferably from about 0.1% to about 2.5% by weight, result in high chroma values ​​C in reflected light. *This ensures the creation of a security feature that exhibits a metallic yellow color having a

[0153] The UV-Vis radiation curable inks described herein may contain up to 25 wt. % organic solvent, where the weight percent is based on the total weight of the UV-Vis radiation curable ink. The organic solvent has a boiling point greater than 100° C. Organic solvents suitable for use in the UV-Vis radiation curable inks described herein include, but are not limited to, ethyl-3-ethoxypropionate, 2-methoxy-1-methylethyl acetate, propylene glycol monomethyl ether, triethylene glycol divinyl ether, cyclopentanone, cyclohexanone, n-butanol, cyclohexanol, ethylene carbonate, propylene carbonate, butylene carbonate, and mixtures thereof.

[0154] In a preferred embodiment according to the present invention, the UV-Vis radiation curable inks used in the inventive manufacturing methods described and claimed herein are solvent-free. The use of solvent-free inks in industrial printing processes for valuable documents is of great interest to prevent the emission of volatile organic components, which are typically harmful to the environment and hazardous to human health.

[0155] The UV-Vis-curable inks and UV-Vis-hybrid inks described herein may further include one or more photosensitizers in combination 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 rapid curing with an ultraviolet LED light source, such as thioxanthone derivatives, anthracene derivatives, and naphthalene derivatives (e.g., 9,10-diethoxyanthracene sold as Anthracure UVS-1101 and 9,10-dibutyloxyanthracene sold as Anthracure UVS-1331, both sold by Kawasaki Chemical Industries, Ltd.), and titanocene derivatives (e.g., Irgacure 784, sold by BASF). Particularly preferred are thioxanthone derivatives, including, but not limited to, isopropyl-thioxanthone (ITX), 1-chloro-2-propoxy-thioxanthone (CPTX), 2-chloro-thioxanthone (CTX), and 2,4-diethyl-thioxanthone (DETX), and mixtures thereof. Alternatively, the thioxanthone photosensitizer may be used in oligomeric or polymeric form (e.g., Omnipol TX available from IGM Resins, Genopol* TX-2 available from Rahn, or Speedcure 7010 available from Lambson). When present, the one or more photosensitizers are preferably present in an amount of about 0.1% to about 2% by weight, more preferably about 0.2% to about 1% by weight, the weight percentages being based on the total weight of the UV-Vis radiation curable ink.

[0156] The UV-Vis radiation curable inks described herein may further include one or more anti-foaming agents in an amount less than about 2% by weight, preferably less than about 1% by weight.

[0157] In order to provide a valuable document with anti-smudge properties and / or to protect the security mechanism from physical and chemical attack from the environment, the manufacturing method claimed in the present application preferably comprises steps f) and g) which are carried out after step c): f) applying a curable protective varnish onto the substrate, preferably by a printing process, to form a varnish layer; g) curing the varnish layer obtained in step f) to form a protective coating.

[0158] Examples of suitable curable protective varnishes to be used in step f) and / or methods of applying said curable protective varnishes to a substrate and curing the varnish layer are described in WO2020234211, WO2013127715 and WO02014067715.

[0159] Preferably, the valuable document is selected from banknotes, certificates, tickets, cheques, vouchers, revenue stamps, agreements, identity documents such as passports, identification 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 valuable document is a banknote. The method for generating security features claimed in the present application may also be used to generate security features directly on valuable items. The term "valuable item" refers to packaging material, in particular packaging material for the pharmaceutical, cosmetic, electronics or food industries, which can be protected from counterfeiting and / or illegal copying to ensure the contents of the package, such as, for example, authentic medicines. [Example]

[0160] The present invention will now be described in more detail with reference to the following non-limiting examples: Experiments E1-E40 and Comparative Experiments C1-C8 below detail the preparation of security features by methods using UV-Vis radiation curable screen printing security inks as described herein.

[0161] A. Analytical method A-1.UV-Vis spectroscopy UV-Vis spectra of the dispersions were recorded on a Varian Cary 50 UV-visible spectrophotometer at dispersion concentrations to achieve an optical density of 0.3 to 1.5 in a 1 cm light path.

[0162] A-2.TEM analysis TEM analysis of the dispersions and coatings was carried out on a ZEISS EM910 instrument in bright field mode at an electron beam acceleration voltage of 100 kV. At least two representative images with different magnification scales were recorded for each sample to characterize the predominant particle morphology.

[0163] Particle diameter was determined from TEM images using Fiji image analysis software based on measurements of at least 300 randomly selected particles as the largest dimension of the nanoplatelets oriented parallel to the plane of the image.

[0164] Particle thickness was measured manually from TEM images as the largest dimension of nanoplatelets oriented perpendicular to the plane of the image, based on measurements of at least 50 randomly selected particles.

[0165] B. Preparation and Characterization of Ag Nanoplatelets Silver nanoplatelets were prepared according to the procedure described in WO2020224982, which is described in detail below.

[0166] 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 cooled to −1° C. while stirring at 250 revolutions per minute (RPM, Solution A).

[0167] 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 at room temperature for 10 min.

[0168] 72 g of the product from Example A3 of WO 2006074969 was added, and the resulting mixture was stirred at room temperature for an additional 10 minutes to homogenize. A solution of 30.6 g of silver nitrate in 30 g of deionized water was added all at once, and the mixture was stirred for 10 minutes, resulting in an orange-brown viscous solution. To this solution, 96 g of deionized water was added, followed by 3 g of Struktol SB2080 defoamer, pre-dispersed in 36 g of deionized water. The resulting mixture was cooled to 0°C while stirring at 250 RPM (Solution B).

[0169] Solution B was then administered subsurface to Solution A via a chilled (0°C) dosing tube using a peristaltic pump at a constant rate over 2 hours to obtain a spherical silver nanoparticle dispersion. Solution A was stirred at 250 RPM during pumping.

[0170] After dosing 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 all at once, followed by the addition of 9.6 g ethylenediaminetetraacetic acid (EDTA) in four equal portions spaced 10 min apart.

[0171] After the last portion of EDTA was added, the reaction mixture was stirred at +5° C. for 15 min, then warmed to 35° C. over 30 min and stirred at this temperature for 1 h, at which time hydrogen evolution was complete.

[0172] 3.0 ml of a 30% wt / wt solution of ammonia in water was added, followed by 5.76 g of solid NaOH, and the mixture was stirred at 35° C. for 15 minutes. Then, while maintaining the temperature at 35° C., 180 ml of a 50% wt / wt solution of hydrogen peroxide in water was dosed via a peristaltic pump into the reaction mixture below the liquid surface at a constant rate over 4 hours while stirring at 250 RPM. This resulted in a deep blue dispersion of silver nanoplatelets, which was allowed to cool to room temperature. The formula [ka] 1.23g of the compound (a mixture of CAS80584-88-9 and 80584-89-0) was added and the mixture was stirred at room temperature for 1 hour.

[0173] B-2. Isolation and purification of Ag nanoplatelets B-2a. First Decantation 9.6 g of sodium dodecyl sulfate was added to the reaction mixture, followed by approximately 25 g of anhydrous sodium sulfate powder, all at once, while stirring until the dispersion color changed from blue to pink. The mixture was then kept at room temperature without stirring for 24 hours, allowing the solidified nanoplatelets to settle to the bottom of the reactor.

[0174] 890 g of the supernatant was pumped out of the reactor using a peristaltic pump, and 890 g of deionized water was added to the reactor. The mixture in the reactor was stirred at room temperature for 1 hour to redisperse the coagulated particles.

[0175] B-2b. Second Decantation Approximately 64 g of anhydrous sodium sulfate powder was added in one portion with stirring until the dispersion's transmittance color changed from blue to yellowish pink. The mixture was then maintained at room temperature without stirring for 12 hours, allowing the coagulated nanoplatelets to settle to the bottom of the reactor. 990 g of the supernatant was pumped out of the reactor using a peristaltic pump, and 90 g of deionized water was added to the reactor. The resulting mixture was stirred at room temperature for 30 minutes to redisperse the coagulated particles.

[0176] B-2c. Ultrafiltration in water 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 to a weight of 400 g and ultrafiltered using a polyethersulfone (PES) membrane with a 300 kDa cutoff to obtain a final volume of approximately 50 mL. This procedure was repeated four times to obtain 60 g of Ag nanoplatelet dispersion in water. After ultrafiltration was completed, the formula [ka] 0.17 g of the compound (a mixture of CAS 80584-88-9 and 80584-89-0) was added to the dispersion.

[0177] Ag content 28.9 wt%; yield about 89% based on total silver; solids content (at 250°C) 33.5 wt%; silver purity based on solids at 250°C 86 wt%.

[0178] 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 using a polyethersulfone (PES) membrane with a 300 kDa cutoff to obtain a volume of approximately 50 mL. This procedure was repeated four times to obtain 72 g of Ag nanoplatelet dispersion in isopropanol.

[0179] Ag content 24.1 wt%; solids content (at 250°C) 25.7 wt%; silver purity based on solids at 250°C 93.5 wt%.

[0180] The UV-Vis-NIR spectrum was measured using a 9.8 × 10 -5 M.λ max = 700 nm, with an extinction coefficient of maximum ε = 10200 L / (cm*mol Ag), FWHM = 340 nm in water.

[0181] The average particle size of the Ag nanoplatelets is 93±40 nm, and the average particle thickness is 16±2.5 nm.

[0182] B-2e. Solvent switching to ethyl 3-ethoxypropionate 30 g of the ultrafiltered Ag nanoplatelet dispersion in isopropanol was placed in a 100 mL round-bottom flask and 9 g of ethyl 3-ethoxypropionate was added. The resulting mixture was concentrated in a rotary evaporator at a pressure of 40 mbar and a bath temperature of 40 °C, and the solvent was distilled off until the solid content was adjusted to 40% w / w by adding ethyl 3-ethoxypropionate to obtain Silver Nanoplatelet Dispersion D1.

[0183] B-2f. Solvent switching to Uvacure 1500 (7-oxabicyclo[4.1.0]hept-3-ylmethyl 7-oxabicyclo[4.1.0]heptane-3-carboxylate) 30 g of the ultrafiltered Ag nanoplatelet dispersion in isopropanol was placed in a 100 mL round-bottom flask and 6 g of Uvacure 1500 (Cytec) was added. The resulting mixture was concentrated in a rotary evaporator at 40 mbar pressure and a bath temperature of 40 °C, and the solvent was distilled off until the solid content was adjusted to 50% w / w by adding Uvacure 1500, resulting in silver nanoplatelet dispersion D2.

[0184] C. Preparation of Inks (I1-I33) and Printing of Security Features Ingredients of UV-Vis curable screen printing inks (I1 to I33) [Table 1] JPEG0007754840000044.jpg207148 JPEG0007754840000045.jpg42148

[0185] C1. Study of the effect of heating temperature on the optical properties of security mechanisms (Comparative Experiment C1, and Experiments E1-E6 and E31-E39) C1a. Preparation of Ink I1 Ink I1 was prepared as described below to evaluate the effect of heating temperature on the appearance of the metallic yellow and blue colors exhibited by the security feature in incident and transmitted light, respectively.

[0186] [Table 2]

[0187] The components shown in Table 2a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm for 10 minutes at room temperature to obtain 50 g of Ink 11. Silver nanoplatelet dispersion D1 contains 40 wt% silver nanoplatelets and 60 wt% ethyl-3-ethoxypropionate.

[0188] C1b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing ink I1 was applied independently to 16 transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the 16 printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at the temperatures and for the times indicated in Table 2b below, and then exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0189] C1c. Security mechanism results (optical characteristics) The optical properties of each security feature obtained in section C1b were evaluated independently in reflection, in transmission, and visually using the three tests described below. The results are summarized in Table 2b.

[0190] Reflection measurements were performed using a goniometer (Goniospektrometer Codec WI-10 5&5, Phyma GmbH, Austria). The L of the printed security features was measured at an illumination angle of 22.5° from 0° to the normal to the side of the printed transparent polymer substrate. * a * b * The value was determined. * The value (chroma, which corresponds to a measure of color intensity or color saturation) is calculated according to the CIELAB (1976) color space. * and b * was calculated from the values.

number

[0191] C * The values ​​(reflection 22.5 / 0°) are shown in Table 2b below.

[0192] Transmission measurements were performed using a Datacolor 650 spectrophotometer (parameters: integrating sphere, diffuse illumination (pulsed xenon D65) and 8° field of view, analyzer SP2000 equipped with dual 256-element diode arrays corresponding to wavelengths in the range 360 ​​nm to 700 nm, transmission sampling aperture size 22 mm). * The values ​​(8° transmission) are shown in table (2b) below.

[0193] A visual evaluation was performed by observing each security feature with the naked eye when reflected off a diffuse source (e.g., with light coming through a window without direct sunlight and the observer facing the wall opposite the window). The following colors were observed: - dark brown to brown, with a matte appearance and no metallic effect; - A gold color (i.e., metallic yellow color) with a shiny appearance and a metallic effect. This metallic effect is achieved by a chroma value C at 0° of 22.5 / reflectance higher than about 20. * appears about.

[0194] A visual evaluation was also performed by observing each security feature with the naked eye during transmission. The following colors were observed: - Dull blue: The blue color is weak (but still visible), - Blue (saturation value C at 8° transmission of approximately 20 or more) * ) to dark blue (saturation value C at 8° transmission of about 30 or more) * ): Strong or very strong blue coloration.

[0195] As shown in Table 2b, the security features obtained by the method according to the invention (Experiments E1 to E6 and E31 to E39) exhibited a gold color in reflection and a blue to dark blue color in transmission, while the comparative security feature obtained by a method not according to the invention (Experiment C1) exhibited a blue color in transmission but a low-saturation brown color in reflection, which was not attention-grabbing and not suitable for a dichroic security feature.

[0196] As evidenced for example by experiments E1 to E6 and E31 to E39 according to the invention, by increasing the heating temperature from about 55° C. to about 100° C. and / or by increasing the heating time in step b) of the manufacturing method according to the invention, higher saturation values ​​C in both reflected and transmitted light can be obtained. * A security mechanism having the following can be obtained.

[0197] [Table 3]

[0198] C2. Consideration of the influence of surfactants on the optical properties of security mechanisms (comparative experiments C2-C5 and inventive experiments E7-E8) Inks I2 to I7 were prepared to evaluate the effect of surfactants on the optical properties of the security features.

[0199] C2a. Preparation of Inks I2 to I7 [Table 4]

[0200] The components shown in Table 3a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I2 to I7.

[0201] C2b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I2 to I7 were applied independently to six transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the six printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0202] C2c. Security mechanism results (optical characteristics) The optical properties of the security features obtained in comparative experiments C2 to C5 and experiments E7 to E8 according to the invention were evaluated independently in reflection, in transmission and visually using the test described in item C1c.

[0203] The reflected and transmitted colors and C of the security mechanisms prepared in comparative experiments C2 to C5 and experiments E7 to E8 according to the invention * The values ​​(22.5 / 0° reflection and 8° transmission) are tabulated in Table 3b below.

[0204] [Table 5]

[0205] As shown in Table 3b, the security features obtained in Experiments E7 and E8 according to the present invention, using inks containing perfluoropolyether surfactants functionalized with hydroxyl or methacrylate groups (Fluorolink E10H / I2 and Fluorolink MD700 / I3), exhibited a gold color in reflection and a blue color in transmission. By comparison, security features obtained using inks containing perfluoropolyether anionic surfactants (Fluoroink F10 / I4), perfluoropolyether nonionic surfactants (Fluorolink S10 / I5), or fluorosurfactants lacking a perfluoropolyether backbone and functional groups selected from hydroxyl, acrylate, and methacrylate groups (Dynasylan F8815 / I6 and Dynasylan F8261 / I7), exhibited a blue color in transmission but a dark brown to brown color with a low chroma value in reflection. The dark brown to brown color with a low chroma value in reflection is not eye-catching and therefore not suitable for a dichroic security feature for protecting valuable documents.

[0206] C3. Discussion of the influence of perfluoropolyether surfactant concentration on the optical properties of security mechanisms according to the invention (Comparative Experiment C6 and Inventive Experiments E9-E14) To evaluate the effect of the concentration of perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate on the optical properties of the security features, inks I8-I14 were prepared as described below.

[0207] C3a. Preparation of Inks I8 to I14 [Table 6]

[0208] The components shown in Table 4a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I8 to I14.

[0209] C3b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I8 to I14 were applied independently to seven transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the seven printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0210] C3c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in comparative experiment C6 and experiments E9 to E14 according to the invention were evaluated independently in reflection, in transmission and visually using the test described in item C1c.

[0211] Reflected and transmitted color and saturation values ​​C of the security mechanisms prepared in comparative experiment C6 and experiments E9 to E14 according to the invention * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 4b below.

[0212] [Table 7]

[0213] As shown in Table 4b, the use of the perfluoropolyether surfactant Fluorolink E10H at a concentration of about 0.1% to about 2.5% by weight ensures that the manufacturing method of the present invention produces a security feature that exhibits a metallic yellow color with a high chroma value in reflection and a blue to dark blue color in transmission. In comparison, the security feature obtained in Comparative Experiment C6, which has an ink that does not contain Fluorolink E10H, exhibits a dark brown to brown color with a low chroma value in reflection. Such a color is not noticeable to the general public and cannot be used as a security feature to protect valuable documents.

[0214] C4. Discussion of the influence of the weight percentage of radically curable monomers and oligomers present in the solvent (solvent-containing ink vs. solvent-free ink) and / or UV-Vis curable ink (UV-Vis hybrid curable ink vs. UV-Vis cationic curable ink) on the optical properties obtained and exhibited by the security features (Experiments E15-E16 and E40 according to the invention) Inks I1, I15, and I16 were prepared to evaluate whether the optical effects obtained using solvent-containing UV-Vis radiation hybrid curable inks could be reproduced with solvent-free UV-Vis radiation hybrid curable inks and solvent-free UV-Vis radiation cationic curable inks.

[0215] C4a. Preparation of Inks I15 and I16 [Table 8]

[0216] The components shown in Table 5a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each ink I15 and I16. I15 is a solvent-free UV-Vis ray cationically curable ink, and I6 is a solvent-free UV-Vis ray hybrid curable ink. Ink I1, prepared in section C1a, is a solvent-containing UV-Vis ray hybrid curable ink. Silver nanoplatelet dispersion D2 contains 50 wt% silver nanoplatelets and 50 wt% Uvacure 1500 (alicyclic epoxide).

[0217] C4b. Preparation of security mechanisms The UV-Vis radiation curable screen printing inks I15 and I6 were applied independently to three transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG) using a 160 thread / cm screen (405 mesh). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the three printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80°C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 100 W / cm 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0218] C4c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in experiments E15, E16 and E40 according to the invention were evaluated independently in reflection, in transmission and visually using the test described in section C1c.

[0219] The color and saturation value C of the reflected and transmitted light displayed by the security mechanism * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 5b below.

[0220] [Table 9]

[0221] As shown in Table 5b, the use of the solvent-containing hybrid ink (I1), the solvent-free hybrid ink (I16), or the solvent-free cationic ink (I15) in the manufacturing process does not affect the optical properties of the security feature.

[0222] C5. Consideration of the influence of the ratio of the weight percentage of radically curable monomers and oligomers present in the ink to the weight percentage of cationically curable monomers present in the ink on the optical properties of the security features (Experiments E17 to E20 according to the invention) C5a. Preparation of Inks I17-I20 [Table 10]

[0223] The components shown in Table 6a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I17 to I20.

[0224] C5b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I17 to I20 were applied independently to four transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the four printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0225] C5c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in experiments E17 to E20 according to the invention were evaluated independently in reflection, in transmission and visually using the test described in item C1c.

[0226] The color and saturation value C of the reflected and transmitted light displayed by the security mechanism * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 6b below.

[0227] [Table 11]

[0228] Experiments E17-E20 according to the present invention show that similar optical effects can be obtained by using UV-Vis radiation cationically curable inks (117) or UV-Vis radiation hybrid curable inks (I18-I20) with a ratio of weight percent (wt%) of radically curable mono- and oligomers to weight percent (wt%) of cationically curable monomers of less than about 53:1.

[0229] C6. Consideration of the influence of the type of polyvinyl chloride copolymer on the optical properties of the security mechanism (Comparative Experiment C7 and Experiments E21 to E23 according to the invention) To evaluate the effect of polyvinyl chloride copolymer type on the optical properties of the security features, inks I21-I24 containing different polyvinyl chlorides were prepared as described below.

[0230] C6a. Preparation of Inks I21 to I24 [Table 12]

[0231] The components shown in Table 7a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I21 to I24.

[0232] C6b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I21 to I24 were applied independently to four transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the four printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0233] C6c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in comparative experiment C7 and experiments E21 to E23 according to the invention were evaluated independently in reflection, in transmission and visually using the tests described in item C1c.

[0234] The color and saturation value C of the reflected and transmitted light displayed by the security mechanism * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 7b below.

[0235] [Table 13]

[0236] As shown in Table 7b, to achieve a security feature that exhibits a metallic yellow color in reflection, the polyvinyl chloride copolymer must contain at least about 69% by weight, and preferably at least about 75% by weight, vinyl chloride. The security feature obtained in Comparative Experiment C7, which was made with an ink containing a polyvinyl chloride copolymer with a lower weight percent of vinyl chloride, exhibited a brown color in reflected light, a color that is not noticeable to the general public and cannot be used as a security feature to protect valuable documents.

[0237] C7. Consideration of the influence of polyvinyl chloride copolymer concentration on the optical properties of security mechanisms (Comparative Experiment C8 and Experiments E24 to E27 according to the present invention) C7a. Preparation of Inks I25, I27 to I30 [Table 14]

[0238] The components shown in Table 8a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I25, I27 to I30.

[0239] C6b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I25, I27 to I30 were applied independently to five transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the five printed substrates were independently placed on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0240] C7c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in comparative experiment C8 and experiments E24 to E27 according to the invention were evaluated independently in reflection, in transmission and visually using the test described in item C1c.

[0241] The color and saturation value C of the reflected and transmitted light displayed by the security mechanism * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 8b below.

[0242] [Table 15]

[0243] As shown in Table 8b, the security feature obtained in comparative experiment C8 using an ink that does not contain Vinnol® H14 / 36 exhibits a dark brown to brown color with low chroma values ​​in reflection. Such a color does not attract the public's attention and cannot be used as a security feature to protect valuable documents. The polyvinyl chloride copolymer Vinnol® H14 / 36 ensures that a gold color (i.e., a metallic yellow color) is obtained in reflection. The amount of polyvinyl chloride copolymer has a strong influence on the viscosity of the ink, which for screen printing inks, as in experiments E24 to E27, is preferably between about 100 mPas and about 1000 mPas at 25°C.

[0244] C8. Consideration of the influence of cationic photoinitiators and UV-Vis curing systems on the optical properties of security mechanisms (Experiments E28-E30 according to the present invention) C8a. Preparation of Inks I31 to I33 [Table 16]

[0245] The components shown in Table 9a were mixed and dispersed using a Dispermat CV-3 at 2000 rpm at room temperature for 10 minutes to obtain 50 g of each of inks I31 to I33.

[0246] C8b. Preparation of security mechanisms Using a 160 thread / cm screen (405 mesh), the UV-Vis radiation curable screen printing inks I31 to I33 were applied independently to three transparent polymer substrates (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the three printed substrates were placed independently on a heating plate (Huber PZ28-1) and heated at 80 °C for 10 seconds, after which they were exposed twice to UV-Vis light at a speed of 100 m / min under an IST Metz GmbH oven (two lamps: iron-doped mercury lamp, 200 W / cm). 2 + mercury lamp 200W / cm 2 ), generated security mechanisms.

[0247] Using a 405 threads / cm screen (160 mesh), the UV-Vis radiation curable screen printing ink I32 was applied to a fourth transparent polymer substrate (PET Hostaphan® RN, 50 μm thick, supplied by Putz GmbH + Co. Folien KG). The size of the printed pattern was 5 cm x 5 cm. After the printing step, the fourth print substrate was placed on a heating plate (Huber PZ28-1) and heated at 80°C for 10 seconds, then irradiated with a UV-LED lamp (Phoseon Type FireLine 125x20mm, 395nm, 8W / cm). 2 ) for 2 seconds to create the security feature.

[0248] C8c. Security Mechanism Results (Optical Characteristics) The optical properties of the security features obtained in experiments E28, E29a, E29b and E30 according to the invention were evaluated independently in reflection, in transmission and visually using the tests described in item C1c.

[0249] The color and saturation value C of the reflected and transmitted light displayed by the security mechanism * (Reflection 22.5 / 0° and Transmission 8°) are shown in Table 9b below.

[0250] [Table 17]

[0251] As shown in Table 9b, the security features obtained in experiments E28, E29a, and E30 according to the invention using inks containing a diaryliodonium photoinitiator (I31), a diaryliodonium photoinitiator and a thioxanthone photosensitizer (I32), or a triphenylpyrylium photoinitiator (I33) and cured under a standard mercury lamp exhibit a gold color in reflection and a deep blue color in transmission, with similar saturation values ​​in both reflection and transmission. Curing with a UV-LED lamp or a standard mercury lamp does not affect the optical properties of the security features, as evidenced by experiments E29a and E29b. [Item 1] 1. A method for producing a security feature for protecting a valuable document, the security feature exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, the method comprising the steps of: a) printing a UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a substrate of a value document, preferably by screen printing, rotogravure or flexographic printing, to provide an ink layer; 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 so that the ink layer exhibits a metallic yellow color when viewed in incident light; c) UV-Vis curing the ink layer obtained in step b) to form the security feature. Including, The UV-Vis ray curable ink is i) silver nanoplatelets having an average diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, an average thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and an average aspect ratio of greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii) about 40% to about 75% by weight of either a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more UV-Vis radiation curable compounds other than a cycloaliphatic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least about 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25% by weight of an organic solvent; Including, the weight percentages of ii) and vi) are based on the total weight of the UV-Vis radiation curable ink; method. [Item 2] Item 2. The method according to item 1, wherein the average diameter of the silver nanoplatelets is in the range of 70 to 120 nm with a standard deviation of less than 50%, the 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. [Item 3] The silver nanoplatelets have on their surface a compound represented by the formula (I)

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Claims

1. 1. A method for producing a security feature for protecting a valuable document, the security feature exhibiting a blue color when viewed in transmitted light and a metallic yellow color when viewed in incident light, the method comprising the steps of: a) printing a UV-Vis radiation curable ink onto a transparent or partially transparent area of ​​a value document substrate to provide an ink layer; b) heating the ink layer obtained in step a) at a temperature of 55°C to 100°C for at least 1 second, so that the ink layer exhibits a metallic yellow color when viewed in incident light; c) UV-Vis curing the ink layer obtained in step b) to form the security feature; Including, The UV-Vis ray curable ink is i) silver nanoplatelets having an average diameter in the range of 50-150 nm with a standard deviation of less than 60%, an average thickness in the range of 5-30 nm with a standard deviation of less than 50%, and an average aspect ratio greater than 2.0, wherein the average diameter is determined by transmission electron microscopy and the average thickness is determined by transmission electron microscopy; ii) 40% to 75% by weight of either a cycloaliphatic epoxide or a mixture of a cycloaliphatic epoxide with one or more UV-Vis radiation curable compounds other than a cycloaliphatic epoxide; iii) one or more cationic photoinitiators; and iv) a polyvinyl chloride copolymer containing at least 69% by weight of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of hydroxyl, acrylate, and methacrylate; vi) 0 to 25 wt. % of an organic solvent; Including, the weight percentages of ii) and vi) are based on the total weight of the UV-Vis radiation curable ink; method.

2. The method described in claim 1, wherein the printing in step a) is carried out by a method selected from screen printing, rotary gravure, or flexographic printing.

3. 3. The method of claim 1, wherein the average diameter of the silver nanoplatelets is in the range of 70 to 120 nm with a standard deviation of less than 50%, the 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.

4. The silver nanoplatelets have on their surface a compound represented by the formula (I) 【Chemical 1】 [In the formula, R １ is H, C １ ~C １８ Alkyl, phenyl, C １ ~C ８ Alkylphenyl, or CH ２ COOH, R ２ , R ３ , R ４ , R ５ , R ６ and R ７ are, independently of each other, H, C １ ~C ８ alkyl, or phenyl; Y is O or NR ８ and R ８ is H or C １ ~C ８ is 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. The method of any one of claims 1 to 3, wherein the surface stabilizer is

5. The silver nanoplatelets are prepared by the following steps: d1) In the first step, the structural element 【Chemistry 2】 wherein X represents a group having at least one carbon atom, and the free radical X derived from X is capable of initiating polymerization. polymerizing one or more ethylenically unsaturated monomers in the presence of at least one nitroxyl ether having the formula: d2) In the first step, at least one stable free nitroxyl radical is generated. 【Chemistry 3】 and polymerizing one or more ethylenically unsaturated monomers in the presence of a free radical initiator; wherein at least one monomer used in step d1) or d2) is a C acrylic acid or methacrylic acid １ ~C ６ Alkyl or hydroxy C １ ~C ６ is an alkyl ester, The method of any one of claims 1 to 4, wherein the surface stabilizer is a polymer or copolymer obtainable by a process comprising:

6. The additional steps of: e) modification of the polymer or copolymer prepared in d1) or d2) by transesterification, amidation, hydrolysis or anhydride modification or a combination thereof; The method of claim 5 , comprising:

7. The UV-Vis ray curable ink is Formula (IIb) 【Chemistry 4】 [In the formula, R ２１ａ represents a hydrogen atom, a halogen atom, or C １ ~C ８ an alkoxy group, or C １ ~C ８ is an alkyl group, R ２１ｂ is a hydrogen atom or a group of the formula -CHR ２４ -N(R ２２ ) (R ２３ ) group, R ２２ and R ２３ are, independently of each other, C １ ~C ８ Alkyl, hydroxy C １ ~C ８ an alkyl group or a group of the formula -[(CH ２ CH ２ ) -O] ｎ１ -CH ２ CH ２ -OH group, where n1 is 1 to 5; R ２４ is H or C １ ~C ８ alkyl] Compounds of and Formula (IIc) 【Chemistry 5】 [In the formula, R ２５ may be the same or different in each occurrence and are hydrogen atoms, halogen atoms, C １ ~C １８ Alkyl group, C １ ~C １８ Alkoxy group, or —C(═O)—R ２６ It is the basis, R ２６ represents a hydrogen atom, a hydroxy group, C １ ~C １８ an alkyl group, an unsubstituted or substituted amino group, an unsubstituted or substituted phenyl group, or C １ ~C １８ is an alkoxy group, n3 is an integer from 1 to 4, m3 is an integer from 2 to 4, and the sum of the integers m3 and n3 is 6. Compounds of The method of any one of claims 1 to 6, comprising one or more stabilizers selected from the group consisting of:

8. 8. The method of claim 1, wherein the UV-Vis radiation curable ink comprises silver nanoplatelets at a concentration of 5 wt% to 20 wt%, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

9. The method described in claim 8, wherein the UV-Vis ray curable ink contains silver nanoplatelets at a concentration of 7.5 wt% to 17.5 wt%, the weight percentage being based on the total weight of the UV-Vis ray curable ink.

10. 10. The method of any one of claims 1 to 9, wherein the one or more UV-Vis radiation curable compounds other than the cycloaliphatic epoxide comprise vii) one or more cationically curable monomers other than the cycloaliphatic epoxide, wherein the one or more cationically curable monomers are selected from the group consisting of vinyl ethers, propenyl ethers, cyclic ethers, lactones, cyclic thioethers, vinyl thioethers, propenyl thioethers, hydroxyl-containing compounds, and mixtures thereof.

11. 11. The method of any one of claims 1 to 10, wherein the one or more UV-Vis radiation curable compounds other than the cycloaliphatic epoxide comprise viii) one or more radically curable monomers and / or oligomers, and the UV-Vis radiation curable ink further comprises ix) one or more free-radical photoinitiators.

12. 12. The method of any one of claims 1 to 11, wherein the UV-Vis radiation curable ink comprises polyvinyl chloride copolymer at a concentration of 2.9 wt% to 12 wt%, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

13. The method of claim 12, wherein the UV-Vis radiation curable ink comprises a polyvinyl chloride copolymer at a concentration of 4.9% to 11.6% by weight, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

14. The method of any one of claims 1 to 13, wherein the polyvinyl chloride copolymer is selected from the group consisting of vinyl chloride-vinyl acetate copolymer and vinyl chloride-hydroxyacrylate copolymer.

15. 15. The method of any one of claims 1 to 14, wherein the UV-Vis radiation curable ink comprises a perfluoropolyether surfactant at a concentration of 0.05 wt% to 5 wt%, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

16. The method of claim 15, wherein the UV-Vis radiation curable ink comprises a perfluoropolyether surfactant at a concentration of 0.075% to 5% by weight, the weight percentage being based on the total weight of the UV-Vis radiation curable ink.

17. The method of any one of claims 1 to 16, wherein the UV-Vis radiation curable ink is solvent-free.

18. 18. The method of any one of claims 1 to 17, wherein step c) comprises exposing the ink layer obtained in step b) to UV-Vis light emitted by a UV-Vis light source selected from the group consisting of a mercury lamp, a UV-LED lamp, and an arrangement thereof.

19. Steps f) and g) performed after step c): f) applying a curable protective varnish onto the substrate by a printing process to form a varnish layer; g) curing the varnish layer obtained in step f) to form a protective coating; The method of any one of claims 1 to 18, further comprising:

20. 20. The method according to any one of claims 1 to 19, wherein the document of value is selected from banknotes, certificates, tickets, cheques, vouchers, revenue stamps, agreements, identification documents, admission tickets, public transport tickets, diplomas, and academic certificates.

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