Gravure printing method for manufacturing security features made of acid-dried gravure ink

Abstract

The present invention relates to a method for manufacturing security features on a substrate by means of intaglio printing, the method comprising: step a) of inking an intaglio engraved printing plate with an oxidation drying intaglio ink, wherein the intaglio engraved printing plate is at a printing plate temperature of from about 45°C to about 85°C; step b) of wiping off excess oxidation drying intaglio ink using a wiping system of paper or tissue or using a polymeric wiping cylinder, and cleaning the polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means; step c) of transferring the oxidation drying intaglio ink onto the substrate in the form of security features; and step d) of drying the oxidation drying intaglio ink in the presence of air to form the security features.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to the field of protection of valuable documents from forgery and illegal reproduction. Specifically, the present invention relates to oxidation-drying inks suitable for intaglio printing of valuable documents, and to the field of intaglio printing methods using oxidation-drying inks.

[0002] [Background of the Invention]

[0002] As color copying and printing quality are constantly improving, and also to protect security documents such as banknotes, valuable documents or cards, transport tickets or cards, tax banderols, and product labels that do not have a reproducible effect against forgery, alteration, or illegal reproduction, it has been a conventional practice to incorporate the features of various security means into these documents.

[0003]

[0003] The intaglio printing method refers to a printing method and process particularly used in the field of valuable documents. The intaglio printing method is known to be the most consistent high-quality printing method for creating fine tapered lines, and thus is the printing technology selected for fine designs in the field of security documents, particularly banknotes and stamps. In particular, one of the prominent features of the intaglio printing method is that by using corresponding shallow or deep engravings on the intaglio printing device, the layer thickness of the ink transferred to the substrate can be varied from several micrometers to several tens of micrometers. As described above, the layer thickness of the intaglio-printed security feature thus enables a sufficient amount of material on the substrate for its detection and sensing.

[0004]

[0004] Oxidative drying inks are generally used in the gravure printing process. The ink dries by oxidation in the presence of oxygen, particularly the oxygen in the atmosphere. During the drying process, oxygen combines with one or more components of the ink vehicle, changing the ink to a semi-solid or solid state. This process may be accelerated by the use of drying agents, also known as catalysts such as metal salts, siccative agents, desiccatives, or desiccators in the art, and / or by heat treatment.

[0005]

[0005] Oxidative drying gravure inks may have the problem of so-called "set-off", which is the transfer of ink from one printed sheet stacked on top of another printed sheet, or to the back side of the endless sheet on the web. This problem can be faced by any industrial printing method using oxidative drying inks, but the significant undulations of the gravure-printed pattern may accentuate the set-off problem. In the state-of-the-art oxidative drying gravure inks, the set-off problem has been mainly reduced by optimizing the ink formulation.

[0006]

[0006] There is still a need for a gravure printing method using oxidative drying gravure inks to produce security features that exhibit good drying performance and set-off characteristics to avoid the set-off problem.

[0007] [Summary]

[0007] Accordingly, an object of the present invention is to overcome the deficiencies of the prior art discussed above. This is achieved by utilizing an oxidative drying gravure ink comprising one or more polythiol compounds and one or more fusible waxes.

[0008]

[0008] A method for producing a security feature on a substrate by a gravure printing method, and the security feature obtained by the method are described herein. The method comprises Step a) of inking an intaglio engraved printing plate with an oxidation drying intaglio ink, wherein the intaglio engraved printing plate is at a printing plate temperature of about 45°C to about 85°C, and the oxidation drying intaglio ink comprises i) at least one oxidation drying varnish, ii) one or more drying agents in a total amount of about 0.01 wt-% to about 10 wt-%, iii) one or more polythiol compounds present in an amount greater than 0.5 wt-%, preferably in a total amount of about 0.75 wt-% to about 2 wt-%, and iv) one or more fusible waxes present in a total amount of about 1 wt-% to about 10 wt-% by weight, based on the total weight of the oxidation drying intaglio ink, step a), and wiping off excess oxidation drying intaglio ink using a paper or tissue wiping system or using a polymeric wiping cylinder, and cleaning the polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means, step b), and transferring the oxidation drying intaglio ink onto a substrate in the form of a security feature, step c), and drying the oxidation drying intaglio ink in the presence of air to form a security feature, step d) comprising.

Brief Description of the Drawings

[0009]

Figure 1

[0010] [Detailed Description]

[0009] The following definitions should be used to interpret the meaning of the terms discussed in the description and recited in the claims.

[0011] As used herein, the article "a" indicates not only one but also more than one, and does not necessarily limit the noun being referred to to the singular.

[0012] As used herein, the term "about" means that the quantity or value in question may be the specified value or some other value that is approximately the same. This expression is intended to convey that similar values within ±5% of the value shown promote equivalent results or effects according to the present invention.

[0013] As used herein, the term "and / or" or "or / and" means that any or all of the elements of the group in question may be present. For example, "A and / or B" would mean "only A, or only B, or both A and B".

[0014] As used herein, the term "at least" means one or more, for example one or two or three.

[0015] The term "security feature" is used to represent elements of an image, pattern, or drawing that can be used for authentication purposes.

[0016] The present invention provides an oxidation-drying intaglio ink suitable for an intaglio printing method, particularly for manufacturing security features in valuable documents.

[0017] Also described herein are security features made by the methods described herein and made with the oxidation-drying intaglio ink described herein, as well as valuable documents containing one or more of said security features. Also described herein is the use of the security features described herein for protecting valuable documents from unauthorized or illegal reproduction.

[0018]

[0017] Gravure printing refers to a printing method and process, especially used in the field of printing valuable documents. In the industrial gravure printing method, ink is supplied to a rotating steel cylinder holding a plate engraved with the pattern or image to be printed by one or more selective inking cylinders (multiple available) (or a chamfered cylinder), and each selective inking cylinder is inked with at least one corresponding color.

[0019]

[0018] A method for manufacturing security features and the security features obtained by that method are also described herein. The method described herein includes step a) of inking a gravure engraved printing plate with the oxidation drying gravure ink described herein, wherein the gravure engraved printing plate is at a printing plate temperature of about 45 °C to about 85 °C. Step a) of inking the oxidation drying gravure ink described herein onto a substrate such as that described herein is typically performed by a gravure having zones of various engraving depths and / or widths.

[0020]

[0019] This method further includes step b) of wiping off excess oxidation drying gravure ink using a paper or tissue wiping system or using a polymeric wiping cylinder, and cleaning the polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means, wherein the wiping step is performed after step a). Preferably, step b) of wiping off excess oxidation drying gravure ink is performed by using a polymeric wiping cylinder and cleaning the polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means. The wiping cylinder is typically a cylinder coated with a material to which ink adheres easily (such as polyvinyl chloride (PVC), etc.), the alkaline aqueous wiping solution typically contains caustic soda and a surfactant (such as sulfated / sulfonated castor oil, etc.), and the mechanical means may be one or more brushes and / or pads (such as Scotch-Brite (trademark) pads).

[0021]

[0020] This method further includes step c) of transferring the oxidative drying gravure ink onto a substrate in the form of a security feature, and the drying step is performed after step b). Step c) consists of contacting a substrate, which may be in sheet or web form, with a gravure engraved printing plate so as to transfer the oxidative drying gravure ink under pressure onto the substrate to be printed from the engraved portion of the printing plate, thereby forming a security feature in the form of a thick relief printing pattern on the substrate. Typically, the security feature is placed on the substrate with very high pressure.

[0022]

[0021] This method further includes step d) of drying the oxidative drying gravure ink described herein in the presence of air to form a layer or coating on a substrate in the form of the security feature described herein, and the drying step d) is performed after step c). The step d) of drying the oxidative drying gravure ink described herein may be performed under hot air, or by an infrared source, or by any combination of hot air and an infrared source to shorten the drying time of the ink.

[0023]

[0022] The oxidative drying gravure ink for the gravure printing method described herein has a viscosity in the range of about 3 to about 60 Pa s at 40 °C and 1000 s -1 The viscosity is measured at a shear rate of 1000 s -1 using a Haake Roto Visco RV1 rotational rheometer with a cone plate of 20 mm diameter and a geometry of 0.5° and at a temperature of 40 °C. The oxidative drying gravure ink described herein includes at least one oxidative drying varnish such as those described herein, one or more drying agents such as those described herein, one or more polythiol compounds such as those described herein, one or more fusible waxes such as those described herein, and optionally one or more compounds, additives, and / or components such as those described herein.

[0024] [

[0023] ]The oxidation-drying gravure ink described herein contains at least one oxidation-drying varnish. The term "varnish" is also referred to as resin, binder, or ink vehicle in the art. The at least one oxidation-drying varnish is preferably present in the oxidation-drying gravure ink described herein in an amount of about 10 to about 90 wt-%, and the weight percentage is based on the total weight of the oxidation-drying gravure ink.

[0025] [

[0024] ]The oxidation-drying varnish is typically a polymer containing unsaturated fatty acid residues, saturated fatty acid residues, or mixtures thereof, as generally known in the art. Preferably, the oxidation-drying varnish described herein contains unsaturated fatty acid residues to ensure air-drying properties. Particularly preferred oxidation-drying varnishes are resins containing unsaturated acid groups, and even more preferably resins containing unsaturated carboxylic acid groups. However, the resin may also contain saturated fatty acid residues. Preferably, the oxidation-drying varnish described herein contains acid groups, i.e., the oxidation-drying varnish is selected from among acid-modified resins. The oxidation-drying varnishes described herein may be selected from the group consisting of alkyd resins, vinyl polymers, polyurethane resins, hyperbranched resins, rosin-modified maleic resins, rosin-modified phenolic resins, rosin esters, petroleum resin-modified rosin esters, petroleum resin-modified alkyd resins, alkyd resin-modified rosin / phenolic resins, alkyd resin-modified rosin esters, acrylic-modified rosin / phenolic resins, acrylic-modified rosin esters, urethane-modified rosin / phenolic resins, urethane-modified rosin esters, urethane-modified alkyd resins, epoxy-modified rosin / phenolic resins, epoxy-modified alkyd resins, terpene resins, nitrocellulose resins, polyolefins, polyamides, acrylic resins, and combinations or mixtures thereof. Polymers and resins are used interchangeably herein.

[0026]

[0025] Saturated and unsaturated fatty acid compounds may be obtained from natural and / or artificial sources. Natural sources include animal and / or plant sources. Animal sources may include animal fat, butterfat, fish oil, lard, liver fat, tuna fish oil, sperm whale oil, and / or tallow oil. Plant sources may include oils, such as vegetable oils and / or non-vegetable oils. Examples of vegetable oils include, but are not limited to, bitter melon, borage, calendula, canola, castor, Chinawood, coconut, conifer seeds, corn, cottonseed, dehydrated castor, flaxseed, grapeseed, jacaranda seed, linseed oil, palm, palm kernel, peanut, pomegranate seed, rapeseed, safflower, triticum vulgare, soybean, sunflower, tall, tung, and wheat germ. Artificial sources include distilled tall oil and / or chemical or biochemical synthetic methods. Suitable fatty acids include myristoleic acid (C 14 H 26 O2, CAS No. 544-64-9), Palmitoleic Acid (C 16 H 30 O2, CAS No. 373-49-9), Oleic Acid (C 18 H 34 O2, CAS No. 112-80-1), α-eleostearic acid (C 18 H 30 O2, CAS No. 506-23-0), Licanic Acid (C 18 H 28 O3, CAS No. 623-99-4), Linoleic acid (C 18 H 32 O2, CAS No. 60-33-3), Linolenic acid (C 18 H 30 O2, CAS No. 463-40-1), stearidonic acid (C 18 H 28 O2, CAS No. 20290-75-9), arachidonic acid (C 20 H 32 O2, CAS No. 506-32-1), Ricinoleic Acid (C 18 H 34 O3, CAS No. 141-22-0), erucic acid (C 22 H 42 O2, CAS No. 112-86-7), Gadoleic acid (C20 H 38 O2, CAS No 29204-02-2), kurpanonic acid (C 22 H 34 O2, CAS No 24880-45-3), nisinic acid (C 24 H 36 O2, CAS No 68378-49-4), and mixtures thereof are also included. These fatty acids are typically used in the form of mixtures of fatty acids derived from natural or synthetic oils.

[0027]

[0026] The oxidative drying gravure ink described herein contains one or more polythiol compounds, and "polythiol compound" refers to a chemical compound having at least two thiol functional groups (-SH) per molecule, and is also called a polyfunctional mercapto compound in the art. Preferably, the one or more polythiol compounds described herein are selected from the group consisting of dithiol compounds (i.e., compounds containing two thiol functional groups), trithiol compounds (i.e., compounds containing three thiol functional groups), tetrathiol compounds (i.e., compounds containing four thiol functional groups), pentathiol compounds (i.e., compounds containing five thiol functional groups), hexathiol compounds (i.e., compounds containing six thiol functional groups), and mixtures thereof, and more preferably are selected from the group consisting of dithiol compounds, trithiol compounds, tetrathiol compounds, and mixtures thereof.

[0028]

[0027] Preferred examples of the dithiol compound are 3-oxa-1,5-pentanedithiol (CAS No 111-46-6), 1,5-pentanedithiol (CAS No 928-98-3), 1,3-pentanedithiol (CAS No 188194-74-3), 1,6-hexanedithiol (CAS No 1191-43-1), 4-mercapto-cyclohexaneethanethiol (CAS No 3232-05-1), 3-mercapto-cyclohexaneethanethiol (CAS No 17809-99-3), 2,2'-thiobis(ethanethiol) (CAS No 3570-55-6), 1-[(2-mercaptoethyl)thio]-2-propanethiol (CAS No 35330-71-3), 1,1'-thiobis[2-propanethiol] (CAS No 35330-70-2), 2,2'-[1,2-ethanediylbis(thio)]bis[ethanethiol] (CAS No 25423-55-6), 2,2'-[thiobis(2,1-ethanediylthio)]bis[ethanethiol] (CAS No 60147-09-3), bis-(4-mercaptomethylphenyl) ether (CAS No 7344-22-1), ethylene glycol bis(3-mercaptoacetate) (CAS No 123-81-9, commercially available as THIOCURE (registered trademark) GDMA from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), propanoic acid, 3-mercapto-, 1,1'-(1,6-hexanediyl) ester (CAS No 96663-89-7); propanoic acid, 3-mercapto-, 1,1'-(1,4-cyclohexanediyl) ester (CAS No 2227318-91-2); propanoic acid, 3-mercapto-, 1,1'-[(1-methylethylidene)di-4,1-cyclohexanediyl] ester (CAS No 24293-42-3), and ethylene glycol bis(3-mercaptopropionate) (CAS No 22504-50-3, commercially available as THIOCURE (registered trademark) GDMP from BRUNO BOCK Chemische Fabrik GmbH & Co. KG).Preferably, the one or more dithiol compounds are esters of mercaptopropionic acid and a polyol, preferably esters with a disubstituted polyol. More preferably, the one or more dithiol compounds are selected from the group consisting of ethylene glycol bis(mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), and mixtures thereof, and more preferably, at least one of the one or more dithiol compounds is ethylene glycol dimercaptoacetate or ethylene glycol bis( mercaptopropionate), and even more preferably ethylene glycol bis(3-mercaptopropionate).

[0029]

[0028] Preferred examples of the trithiol compounds are glycerin trimercaptoacetate (CAS No 14974-53-9), glycerin trimercaptopropionate (CAS No 26424-84-0), trimethylolpropane trimercaptoacetate (CAS No 10193-96-1, commercially available as THIOCURE® TMPMA from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), trimethylolpropane tris-3-mercaptopropionate (CAS No 33007-83-9, commercially available as THIOCURE® TMPM from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), ethoxylated trimethylolpropane tris-3-mercaptopropionate (CAS No 345352-19-4, commercially available as THIOCURE® ETTMP from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate (CAS No 36196-44-8, commercially available as THIOCURE® TEMPIC from BRUNO BOCK Chemische Fabrik GmbH & Co. KG). Preferably, the one or more trithiol compounds are selected from the group consisting of trimethylolpropane tris-3-mercaptopropionate, ethoxylated trimethylolpropane tris-3-mercaptopropionate, tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, and mixtures thereof, and even more preferably tris[2-(3-mercaptopropionyloxy)-ethyl] isocyanurate.

[0030]

[0029] Preferred examples of the tetrathiol compound include pentaerythritol tetra(mercaptoacetate) (CAS No 10193-99-4, commercially available as THIOCURE® PETMA from BRUNO BOCK Chemische Fabrik GmbH&Co.KG), pentaerythritol tetra(3-mercaptopropionate) (CAS No 7575-23-7, commercially available as THIOCURE® PETMP and THIOCURE® 340 from BRUNO BOCK Chemische Fabrik GmbH&Co.KG), pentaerythritol tetra(4-mercaptobutanoate) (CAS No 916903-92-9), and polycaprolactone tetra(3-mercaptopropionate) (CAS No 1622079-69-9, commercially available as THIOCURE® PCL4MP 1350 from BOCK Chemische Fabrik GmbH&Co.KG). More preferably, they are pentaerythritol tetra(2-mercaptoacetate) and pentaerythritol tetra(3-mercaptopropionate), and even more preferably, pentaerythritol tetra(3-mercaptopropionate).

[0031]

[0030] Preferred examples of the polythiol compound having more than four thiol functional groups (-SH) per molecule include dipentaerythritol hexa(3-mercaptopropionate) (CAS No 25359-71-1, commercially available as THIOCURE® DiPETMP from BRUNO BOCK Chemische Fabrik GmbH&Co.KG).

[0032]

[0031] The oxidative drying intaglio ink described in this specification preferably contains one or more polythiol compounds selected from the group consisting of dithiol compounds, trithiol compounds, tetrathiol compounds, and mixtures thereof, more preferably compounds such as those described above. According to one embodiment, at least one dithiol compound is ethylene glycol bis(3-mercaptopropionate), and / or at least one trithiol compound is tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, and / or at least one tetrathiol compound is pentaerythritol tetra(3-mercaptopropionate).

[0033]

[0032] One or more thiol compounds are present in a total amount of more than about 0.5 wt-%, preferably about 0.75 wt-% to about 2 wt-%, more preferably about 1 wt-% to 2 wt-%, based on the weight percentage of the total weight of the oxidative drying intaglio ink.

[0034]

[0033] The oxidative drying intaglio ink described in this specification contains one or more fusible waxes. Within the scope of the context of the present invention, one or more fusible waxes refer to a wax or a mixture of waxes having a melting temperature of about 50°C to about 120°C. One or more fusible waxes are preferably selected from the group consisting of synthetic waxes, petroleum waxes, and natural waxes. Preferably, one or more waxes are selected from the group consisting of microcrystalline wax, paraffin wax, polyethylene wax, fluorocarbon wax, polytetrafluoroethylene wax, Fischer-Tropsch wax, silicone fluid, beeswax, candelilla wax, montan wax, carnauba wax, rice bran wax, and mixtures thereof. One or more waxes are present in a total amount of about 1 wt-% to about 10 wt-%, preferably about 1.5 wt-% to 8 wt-%, more preferably about 2 wt-% to 6 wt-%, based on the weight percentage of the total weight of the oxidative drying intaglio ink.

[0035]

[0034] The oxidative drying security ink dries by oxidation in the presence of oxygen, particularly in the presence of atmospheric oxygen. During the drying process, oxygen combines with one or more components of the ink, changing the ink to a solid state. The oxidative drying gravure ink described herein includes one or more drying agents (also referred to in the art as catalysts, siccatives, siccative agents, desiccatives, or desiccators) to speed up the oxidation process. Examples of drying agents include inorganic or organic salts of metal(s), metal soaps of organic acids, metal complexes, and metal complex salts. Suitable salts of metal(s) include cobalt, calcium, copper, zinc, iron, zirconium, manganese, barium, zinc, strontium, lithium, vanadium, and potassium as cation(s); and halide, nitrate, sulfate, carboxylate, such as acetate, ethylhexanoate, octanoate, and naphthenate, or salts containing acetoacetonate, such as ethylhexanoates of cobalt, manganese, and zirconium as anion(s). Suitable examples of metal complexes and metal complex salts include manganese, vanadium, and iron compounds (i.e., manganese complexes, manganese complex salts, vanadium complexes, vanadium complex salts, iron complexes, and iron complex salts). When present, the one or more drying agents used in the oxidative drying gravure ink described herein are preferably present in a total amount of about 0.01 wt-% to about 10 wt-%, more preferably in a total amount of about 0.1 wt-% to about 5 wt-%, based on the total weight of the oxidative drying gravure ink, where the weight percentages are based on the total weight of the oxidative drying gravure ink.

[0036]

[0035] According to one embodiment, the oxidative drying intaglio ink described herein is a white, transparent, or slightly colored ink, enabling the preparation of white, transparent, or slightly colored security features. According to one embodiment, the oxidative drying intaglio ink described herein is a white ink. According to one embodiment, the oxidative drying intaglio ink described herein is a transparent ink. According to one embodiment, the oxidative drying intaglio ink described herein is a slightly colored ink. Preferably, the white, transparent, or slightly colored ink contains one or more drying agents selected from the group consisting of iron compounds, manganese compounds, zirconium compounds, and mixtures thereof, and the compounds may be inorganic or organic salts of metal(s), metal soaps of organic acids, metal complexes and metal complex salts as described above.

[0037]

[0036] The oxidative drying intaglio ink described herein preferably comprises one or more fillers and / or extenders selected from the group consisting of talc, mica (e.g., muscovite), montmorillonite, bentonite, wollastonite, halloysite, calcined clay, china clay, carbonates (e.g., calcium carbonate, magnesium carbonate), silicates (e.g., magnesium silicate, aluminum silicate), vermiculite, amorphous silica (e.g., fumed silica, precipitated silica, silica sand powder), wood flour, natural fibers, synthetic fibers (such as carbon fibers or carbon nanotubes), and mixtures thereof; preferably selected from the group consisting of talc, mica, wollastonite, calcined clay, carbonates, amorphous silica, and mixtures thereof.

[0038]

[0037] When present, the one or more fillers or extenders are preferably present in a total amount of about 0.1 wt-% to about 50 wt-%, more preferably about 20 wt-% to about 40 wt-%, based on the total weight of the oxidative drying intaglio ink, where the weight percentages are based on the total weight of the oxidative drying intaglio ink.

[0039]

[0038] The oxidative drying gravure ink described in this specification may further contain one or more surfactants, particularly hydrophilic polymer surfactants such as those described in European Patent No. 0340163B1. The role of the optional surfactant is to assist in wiping off the excess ink present on the printing cylinder immediately before bringing the printing cylinder into contact with the substrate. This process of wiping off the excess ink is part of any high-speed industrial gravure printing method and is carried out using a roll of tissue or paper ("calico") or a polymer wiping cylinder and a cleaning aqueous solution ("wiping solution"). In this case, the optional surfactant is used to emulsify the excess ink in the cleaning solution. The surfactant may be not only nonionic, anionic, or cationic, but also zwitterionic. In the case of a hydrophilic polymer surfactant, the functional groups are, for example, carboxylic acid or sulfonic acid groups, hydroxyl groups, ether groups, or primary, secondary, tertiary, or quaternary amino groups. The acid groups may be neutralized by amines, alkanolamines, or preferably inorganic bases, or combinations thereof. The primary, secondary, and tertiary amino groups may be neutralized by inorganic or organic acids such as sulfonic acid, formic acid, acetic acid, trifluoroacetic acid, and others. Particularly preferred are anionic polymer surfactants (AMS) such as those described in European Patent Application Publication No. 2014729A1.

[0040]

[0039] The oxidative drying gravure ink described in this specification may be a color constant ink or an optically variable ink. In other words, the oxidative drying gravure ink may further contain one or more coloring components selected from the group consisting of optically variable pigments, color constant pigments, color constant dyes, and mixtures thereof, preferably selected from the group consisting of color constant organic pigments, color constant inorganic pigments, and mixtures thereof.

[0041]

[0040] According to one aspect of the present invention, the oxidative drying intaglio ink described herein is a non-discoloring ink, which may be a white, transparent, or slightly colored ink, or a colored ink. According to one embodiment, the oxidative drying intaglio ink described herein is a non-discoloring white ink. According to one embodiment, the oxidative drying intaglio ink described herein is a non-discoloring transparent ink. According to one embodiment, the oxidative drying intaglio ink described herein is a non-discoloring slightly colored ink. According to one embodiment, the oxidative drying intaglio ink described herein is preferably a non-discoloring composition ink containing a) one or more dyes, and / or b) inorganic pigments, organic pigments, or mixtures thereof. Dyes suitable for the ink are known in the art and are preferably selected from the group consisting of reactive dyes, direct dyes, anionic dyes, cationic dyes, acid dyes, basic dyes, food colorants, metal complex dyes, solvent dyes, and mixtures thereof. Typical examples of suitable dyes include, but are not limited to, coumarin, cyanine, oxazine, uranine, phthalocyanine, indolinocyanine, triphenylmethane, naphthalocyanine, indonaphthalometal dyes, anthraquinone, anthrapyridone, azo dyes, rhodamine, squarylium dyes, croconium dyes. Examples of dyes suitable for the present invention include, but are not limited to, C.I. Acid Yellow 1, 3, 5, 7, 11, 17, 19, 23, 25, 29, 36, 38, 40, 42, 44, 49, 54, 59, 61, 70, 72, 73, 75, 76, 78, 79, 98, 99, 110, 111, 121, 127, 131, 135, 142, 157, 162, 164, 165, 194, 204, 236, 245; C.I. Direct Yellow 1, 8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 58, 85, 86, 87, 88, 89, 98, 106, 107, 110, 132, 142, 144; C.I. Basic Yellow 13, 28, 65; C.I. Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42; C.I. Food Yellow 3, 4; C.I. Acid Orange 1, 3, 7, 10, 20, 76, 142, 144; C.I. Basic Orange 1, 2, 59; C.I.Food Orange 2; C.I. Orange B; C.I. Acid Red 1, 4, 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 37, 42, 51, 52, 57, 73, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94, 97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138, 143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211, 215, 219, 221, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321, 322, 357, 359; C.I. Basic Red 1, 2, 14, 28; C.I. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33, 37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197, 201, 218, 220, 224, 225, 226, 227, 228, 229, 230, 231, 253; C.I. Reactive Red 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23, 24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46, 49, 50, 58, 59, 63, 64, 108, 180; C.I. Food Red 1, 7, 9, 14; C.I. Acid Blue 1, 7, 9, 15, 20, 22, 23, 25, 27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92, 93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131, 138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182, 183, 184, 187, 192, 193, 199, 203, 204, 205, 229, 234, 236, 249, 254, 285; C.I. Basic Blue 1, 3, 5, 7, 8, 9, 11, 55, 81; C.I.Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196, 199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, 249; C.I. Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20, 21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, 46, 77; C.I. Food Blue 1, 2; C.I. Acid Green 1, 3, 5, 16, 26, 104; C.I. Basic Green 1, 4; C.I: Food Green 3; C.I. Acid Violet 9, 17, 90, 102, 121; C.I. Basic Violet 2, 3, 10, 11, 21; C.I. Acid Brown 101, 103, 165, 266, 268, 355, 357, 365, 384; C.I. Basic Brown 1; C.I. Acid Black 1, 2, 7, 24, 26, 29, 31, 48, 50, 51, 52, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108, 109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156, 157, 158, 159, 191, 194; C.I. Direct Black 17, 19, 22, 32, 39, 51, 56, 62, 71, 74, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132, 133, 146, 154, 168; C.I. Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 18, 31; C.I. Food Black 2; C.I. Solvent Yellow 19, C.I. Solvent Orange 45, C.I. Solvent Red 8, C.I. Solvent Green 7, C.I. Solvent Blue 7, C.I. Solvent Black 7; C.I. Disperse Yellow 3, C.I. Disperse Red 4, 60, C.I.Examples include Disperse Blue 3 and metal azo dyes disclosed in U.S. Patent No. 5,074,914, U.S. Patent No. 5,997,622, U.S. Patent No. 6,001,161, Japanese Patent Laid-Open No. 02-080470, Japanese Patent Laid-Open No. 62-190272, and Japanese Patent Laid-Open No. 63-218766. Suitable dyes in the present invention may be infrared-absorbing dyes or luminescent dyes. When present, one or more dyes used in the oxidative drying gravure ink described herein are preferably present in a total amount of about 1 wt% to about 20 wt%, based on the total weight of the oxidative drying gravure ink, by weight percentage.

[0042]

[0041] Typical examples of organic and inorganic pigments include, but are not limited to, C.I. Pigment Yellow 12, C.I. Pigment Yellow 42, C.I. Pigment Yellow 93, C.I. Pigment 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 147, C.I. Pigment Yellow 173, C.I. Pigment Orange 34, C.I. Pigment Orange 48, C.I. Pigment Orange 49, C.I. Pigment Orange 61, C.I. Pigment Orange 71, C.I. Pigment Orange 73, C.I. Pigment Red 9, C.I. Pigment Red 22, C.I. Pigment Red 23, C.I. Pigment Red 67, C.I. Pigment Red 122, C.I. Pigment Red 144, C.I. Pigment Red 146, C.I. Pigment Red 170, C.I. Pigment Red 177, C.I. Pigment Red 179, C.I. Pigment Red 185, C.I. Pigment Red 202, C.I. Pigment Red 224, C.I. Pigment Brown 6, C.I. Pigment Brown 7, C.I. Pigment Red 242, C.I. Pigment Red 254, C.I. Pigment Red 264, C.I. Pigment Brown 23, C.I. Pigment Blue 15, C.I. Pigment Blue 15:3, C.I. Pigment Blue 60, C.I. Pigment Violet 19, C.I. Pigment Violet 23, C.I. Pigment Violet 32, C.I. Pigment Violet 37, C.I. Pigment Green 7, C.I. Pigment Green 36, C.I. Pigment Black 7, C.I. Pigment Black 11, Pigment Black 31, Pigment Black 32, C.I. Pigment White 4, C.I Pigment White 6, C.I. Pigment White 7, C.I. Pigment White 21, C.I.Pigment White 22, antimony yellow, lead chromate, lead chromate sulfate, lead molybdate, ultramarine, cobalt blue, manganese blue, chromium oxide green, hydrated chromium oxide green, cobalt green, cerium sulfide, cadmium sulfide, cadmium thioselenide, zinc ferrite, bismuth vanadate, Prussian blue, mixed metal oxides, azo, azomethine, methine, anthraquinone, phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazine indigo, dioxazine, iminoisoindoline, iminoisoindolinone, quinacridone, flavanthrone, indanthrone, anthrapyrimidine, and quinophthalone pigments. When present, the inorganic pigments, organic pigments, or mixtures thereof described herein are preferably present in a total amount of about 0.1 wt-% to about 45 wt-%, based on the total weight of the oxidative drying gravure ink.

[0043]

[0042] In embodiments where the oxidative drying gravure ink described herein is a transparent ink, the ink typically does not contain any pigments such as those described herein. In embodiments where the oxidative drying gravure ink described herein is a white or slightly colored ink, the ink preferably contains one or more pigments selected from the group consisting of C.I. Pigment White 4, C.I Pigment White 6, C.I. Pigment White 7, C.I. Pigment White 21, and C.I. Pigment White 22.

[0044]

[0043] According to one aspect of the present invention, the oxidative drying gravure ink described herein is an optically variable ink and contains an optically variable pigment or a mixture of various optically variable pigments. The optically variable ink may further contain one or more non-color-changing pigments. The optically variable ink preferably contains an optically variable pigment or a mixture of various optically variable pigments, and the optically variable pigment is preferably selected from the group consisting of thin film interference pigments, interference coating pigments, cholesteric liquid crystal pigments, and mixtures thereof. When present, the optically variable pigment is preferably contained in the oxidative drying gravure ink described herein in an amount of about 5 wt-% to about 40 wt-%, more preferably about 10 wt-% to about 35 wt-% of the total amount, and the weight percentage is based on the total weight of the oxidative drying gravure ink.

[0045]

[0044] Suitable thin film interference pigments showing optical variable properties are known to those skilled in the art and are disclosed in U.S. Patent No. 4,705,300; U.S. Patent No. 4,705,356; U.S. Patent No. 4,721,271; U.S. Patent No. 5,084,351; U.S. Patent No. 5,214,530; U.S. Patent No. 5,281,480; U.S. Patent No. 5,383,995; U.S. Patent No. 5,569,535, U.S. Patent No. 5,571,624, and related documents. When at least a part of the optical variable pigment consists of a thin film interference pigment, the thin film interference pigment preferably includes a Fabry - Perot reflector / dielectric / absorber multilayer structure, more preferably a Fabry - Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure. The absorber layer is partially transmissive and partially reflective, the dielectric layer is transmissive, and the reflector layer reflects incident light. Preferably, the reflector layer is selected from the group consisting of metals, metal alloys, and combinations thereof, preferably selected from the group consisting of reflective metals, reflective metal alloys, and combinations thereof, more preferably selected from the group consisting of aluminum (Al), chromium (Cr), nickel (Ni), and mixtures thereof, and even more preferably aluminum (Al). Preferably, the dielectric layer is independently selected from the group consisting of magnesium fluoride (MgF2), silicon dioxide (SiO2), and mixtures thereof, and more preferably magnesium fluoride (MgF2). Preferably, the absorber layer is independently selected from the group consisting of chromium (Cr), nickel (Ni), metal alloys, and mixtures thereof, and more preferably chromium (Cr). When at least a part of the optical variable pigment consists of a thin film interference pigment, it is particularly preferred that the thin film interference pigment includes a Fabry - Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure having a Cr / MgF2 / Al / MgF2 / Cr multilayer structure.

[0046]

[0045] The thin film interference pigments described herein are typically manufactured by vacuum depositing the various required layers onto a web. After forming the desired number of layers, the laminate is removed from the web by dissolving the release layer in a suitable solvent or by peeling the material from the web. The material thus obtained is then broken up into flakes, which need to be further processed by grinding, milling, or any suitable method. The resulting product consists of flat flakes with broken edges, irregular shapes, and various aspect ratios.

[0047]

[0046] Suitable interference coating pigments include, but are not limited to, structures composed of substrates selected from the group consisting of metals such as titanium, silver, aluminum, copper, chromium, iron, germanium, molybdenum, tantalum, or nickel, coated with one or more layers made of metal oxides; and structures composed of cores made of synthetic or natural mica, other layered silicates (such as talc, kaolin, and sericite), glass (such as borosilicate), silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum oxide / hydroxide aluminum (boehmite), titanium oxide (TiO2), graphite, and mixtures thereof, coated with one or more layers made of metal oxides (such as titanium oxide, zirconium oxide, tin oxide, chromium oxide, nickel oxide, copper oxide, iron oxide, and iron oxide / hydroxide iron). The above structures are described, for example, in Chem. Rev. 99 (1999), G. Pfaff and P. Reynders, pages 1963 - 1981, and International Publication No. WO 2008 / 083894 A2. Typical examples of these interference coating pigments include, but are not limited to, silicon oxide cores coated with one or more layers made of titanium oxide, tin oxide, and / or iron oxide; natural or synthetic mica cores coated with one or more layers made of titanium oxide, silicon oxide, and / or iron oxide, particularly mica cores coated with alternating layers made of silicon oxide and titanium oxide; borosilicate cores coated with one or more layers made of titanium oxide, silicon oxide, and / or tin oxide; titanium oxide cores coated with one or more layers made of iron oxide, iron oxide / hydroxide iron, chromium oxide, copper oxide, cerium oxide, aluminum oxide, silicon oxide, bismuth vanadate, nickel titanate, cobalt titanate, and / or antimony-doped, fluorine-doped, or indium-doped tin oxide; and aluminum oxide cores coated with one or more layers made of titanium oxide and / or iron oxide.

[0048]

[0047] Cholesteric liquid crystals exhibit a molecular order in the form of a helical superstructure perpendicular to the longitudinal axis of their molecules. The helical superstructure is the origin of the periodic refractive index modulation across the entire liquid crystal material, which in turn results in the selective transmission / reflection of a defined light wavelength (interference filter effect). Cholesteric liquid crystal polymers can be obtained by aligning and orienting one or more crosslinkable substances (nematic compounds) having a chiral phase. The specific situation of the helical molecular arrangement results in a cholesteric liquid crystal material that exhibits the property of reflecting circularly polarized components within a defined wavelength range. By varying selectable factors including temperature and solvent concentration, and also by changing the nature of the chiral component(s) and the ratio of the nematic compound to the chiral compound, the pitch can be adjusted. Crosslinking under the influence of UV irradiation freezes the pitch in a predefined state by fixing the desired helical form so that the color of the resulting cholesteric liquid crystal material is no longer dependent on external factors such as temperature. The cholesteric liquid crystal material can then be formed into a cholesteric liquid crystal pigment by grinding the polymer to the desired particle size. Examples of films and pigments made from cholesteric liquid crystal materials and their preparation are disclosed in U.S. Patent No. 5,211,877; U.S. Patent No. 5,362,315 and U.S. Patent No. 6,423,246, and European Patent Application Publication No. 1,213,338A1; European Patent Application Publication No. 1,046,692A1 and European Patent Application Publication No. 0,601,483A1, the respective disclosures of which are incorporated herein by reference.

[0049]

[0048] The oxidative drying gravure ink described herein may further comprise one or more machine-readable components selected from the group consisting of magnetic materials, luminescent materials, conductive materials, infrared absorbing materials, and mixtures thereof.

[0050]

[0049] The oxidative drying gravure ink described herein may further comprise one or more forensic markers and / or one or more taggants.

[0051]

[0050] The oxidative drying gravure ink described in this specification may further contain one or more additives, including, but not limited to, compounds and materials used to adjust the physical, rheological, and chemical parameters of the composition, such as viscosity, consistency (e.g., anti-settling agents and plasticizers), foaming properties (e.g., defoamers and degassing devices), UV stability (light stabilizers), adhesiveness, etc. The additives described in this specification may be present in the oxidative drying gravure ink disclosed herein in known amounts and forms in the art, including in the form of so-called nanomaterials in which at least one of the particle dimensions is in the range of 1 to 1000 nm.

[0052]

[0051] The gravure printing method described herein enables the production of security features on the substrates described herein. The substrates described herein are preferably selected from the group consisting of paper or other fibrous materials (including woven and non-woven fibrous materials), such as cellulose, paper-containing materials, glass, metal, ceramic, plastic and polymer, metallized plastic or polymer, composite materials, and mixtures or combinations of two or more thereof. Typical papers, paper-like, or other fibrous materials are made from various fibers including, but not limited to, manila hemp, cotton, linen, wood pulp, and blends thereof. As is well known to those skilled in the art, cotton and cotton / linen blends are preferred for banknotes, while wood pulp is generally used for non-banknote valuable documents. Typical examples of plastics and polymers include polyolefins such as polyethylene (PE) and polypropylene (PP) including biaxially oriented polypropylene (BOPP), polyamide (PA), polyesters such as poly(ethylene terephthalate) (PET), glycol-modified polyethylene terephthalate (PETG) including poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate), poly(1,4-butylene terephthalate) (PBT), poly(ethylene 2,6-naphthoate) (PEN), etc., and polyvinyl chloride (PVC). Spunbond olefin fibers such as those sold under the trademark Tyvek® may also be used as substrates. Typical examples of metallized plastics or polymers include the above plastic or polymer materials with metal disposed continuously or discontinuously on the surface. Typical examples of metals include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), their alloys, and combinations of two or more of the above metals. The metallization of the above plastic or polymer materials may be carried out by electrodeposition, high vacuum coating, or sputtering. Typical examples of composite materials include, but are not limited to, multi-layer structures or laminates of paper and at least one plastic or polymer material such as the above, and plastics and / or polymer fibers incorporated into fibrous materials such as paper-like materials or the above.Of course, the base material may contain additional additives known to those skilled in the art, such as fillers, sizing agents, bleaching agents, processing aids, strengthening agents, or wet strengthening agents. For the purpose of further improving the security level and resistance against counterfeits and illegal reproductions of valuable documents, the base material may contain watermarks, security threads, fibers, coin floors, luminescent compounds, windows, foils, decals, coatings, and combinations thereof.

[0053]

[0052] Also described herein are a method for manufacturing the oxidation-drying gravure ink described herein and the oxidation-drying gravure ink obtained from that method. The oxidation-drying gravure ink described herein may be prepared by mixing all components except one or more drying agents, dispersing or grinding them using, for example, a three-roll mill, and then adding and mixing one or more drying agents. Alternatively, the oxidation-drying gravure ink described herein may be prepared by mixing all components except one or more polythiol compounds and one or more drying agents, dispersing or grinding them using, for example, a three-roll mill, then adding and mixing one or more polythiol compounds, and then adding and mixing one or more drying agents.

[0054]

[0053] Also described herein are security features made of the oxidation-drying gravure ink described herein and made by the method described herein. Also described herein is the use of the security features described herein for protecting valuable documents from unauthorized or illegal reproduction.

[0055]

[0054] Also described herein are valuable documents containing one or more security features made of the oxidation-drying gravure ink described herein, such as those described herein. Preferably, the valuable document is selected from banknotes, certificates, tickets, checks, gift certificates, revenue stamps, contracts, identity documents such as passports, ID cards, visas, driver's licenses, cash cards, credit cards, transaction cards, access documents, and cards, tickets, public transportation tickets, graduation certificates, and degree certificates. More preferably, the valuable document is a banknote.

[0056]

[0055] The security document described in this specification may further include one or more additional layers or coatings either below or above the security feature made of the oxidative drying gravure ink described in this specification. For example, if the adhesion between the substrate and the security feature described in this specification is insufficient due to the substrate material, surface irregularities, or surface inhomogeneity, an additional layer, coating, or primer may be applied between the substrate and the security feature as known to those skilled in the art.

[0057]

[0056] For the purpose of improving durability by resistance to contamination or chemicals, improving cleanliness, and thereby improving the circulation life of the security document, one or more protective layers may be applied on top of one or more security features described in this specification. When present, the one or more protective layers are typically made of a protective varnish that may be transparent or slightly colored or tinted and may be more or less glossy. The protective varnish may be an electromagnetic radiation curable composition, a heat drying composition, or any combination thereof. Preferably, the one or more protective layers are made of an electromagnetic radiation curable, more preferably a UV-visible light curable composition.

[0058] [Examples]

[0057] The present invention will now be described in more detail with reference to non-limiting examples. The following examples show further details regarding the preparation and use of the oxidative drying gravure ink for printing security features on a substrate by the gravure printing method. In particular, Examples E1 to E22 and Comparative Examples C1 to C27 according to the present invention described hereinafter show further details regarding the preparation, drying characteristics, and color characteristics of the printed samples obtained by the methods described in this specification.

[0059]

[0058] Comparative Examples C28 to C39 were prepared according to a comparative offset method using the oxidative drying offset inks described in Table 10.

[0060] A. Preparation of Oxidative Drying Gravure Ink

[0059] Four compositions, namely, a black pigment paste (PP), a transparent white composition (TW, Table 1), a mixture of desiccants (D, Table 2), and a polythiol compound (TH, Table 3), were used to prepare gravure inks for oxidation drying (I1 - I23, Table 4) which were used to prepare printing samples (E1 - E18 and C1 - C23, Table 6). When manufacturing the transparent white compositions (TW1 - TW4) as described in Table 1, fusible waxes (W1 - W4) were added if present. To produce the final gravure inks (I1 - I23) as described in Table 4, the polythiol compounds (TH1 - TH3) were added to the dispersion mixture of the transparent white compositions (TW0 - TW4) and the black pigment paste (PP) if present, before adding the mixture of desiccants (D1 - D4).

[0061]

[0060] Examples (E1 - E14, Table 6) were prepared using inks containing one or more fusible waxes and one or more polythiol compounds in the required amounts according to the method of the present invention. Comparative examples C1, C5, C9, and C13 - C15 were prepared using inks containing one or more fusible waxes and one or more polythiol compounds according to the comparative method. Comparative examples C2 - C4, C6 - C8, C10 - C12, and C16 - C19 were prepared using inks that followed the method of the present invention but lacked either one or more fusible waxes or one or more polythiol compounds in the required amounts, or both.

[0062]

[0061] Examples (E15 - E18, Table 6) were prepared using inks containing one or more fusible waxes and one or more polythiol compounds in the required amounts according to the method of the present invention. Comparative examples C20 - C23 were prepared using inks containing one or more fusible waxes but lacking one or more polythiol compounds in the required amounts according to the comparative method.

[0063]

[0062] Three types of compositions, an ink premix (IP, Table 7), a mixture of desiccants (D, Table 2), and a polythiol compound (TH, Table 3), were used to prepare the oxidative drying gravure ink (I24 - I31, see Table 8) used to prepare the printed samples (E19 - E22 and C24 - C27). Before adding the mixture of desiccants (D1 - D2), the polythiol compound (TH1) was added to the ink premix (IP1 - IP2) if present, to produce the final gravure ink (I24 - I31) as described in Table 8.

[0064]

[0063] Examples (E19 - E22, Table 9) were prepared using an ink containing one or more fusible waxes and one or more polythiol compounds in the required amounts according to the method of the present invention. Comparative Examples C24 - C27 were prepared using an ink containing one or more fusible waxes but lacking one or more polythiol compounds in the required amounts according to the comparative method. Black pigment paste (PP): 39.1 wt-% urethane alkyd resin consisting of Synres' Urakyd AL210 Q55 (soybean oil-based polyurethane-modified long-oil alkyd resin) 18.4 wt-% phenolic resin consisting of 42.4 wt-% phenol-modified rosin ester (Bremapal 2035, Kraemer) heated in 42.4% tung oil (Interfat, CAS No 8001-20-5) and then diluted with 15.2 wt-% n-dodecane (Halterman, CAS No 112-40-3) 13.8 wt-% CI Pigment Black 7 consisting of Orion's Special Black 4A (CAS No 1333-86-4) Omya's Omyalite® 50 (limestone, CAS No 1317-65-3, particle size d 50 <2 microns) consisting of 28.7 wt-% inorganic filler It contains, first weigh the above components, and mix them with each other at 2500 rpm for 3 minutes using a SpeedMixer (registered trademark) (DAC 150 SP of Hauschild Engineering) at room temperature. Then, in order to produce a black pigment paste (PP), a grinding step was carried out by passing it through a Buhler SDY three-roll mill three times at pressures of 5, 11, and 11 bar respectively.

Table 1

[0065]

[0064] First weigh the components, mix them with each other using a SpeedMixer (registered trademark) (DAC 150 SP of Hauschild Engineering) (at 2500 rpm for 3 minutes), and then prepare a transparent white composition (TW0 - TW4) by passing it through a Buhler SDY three-roll mill three times at pressures of 5, 11, and 11 bar respectively for grinding.

Table 2

Table 3

Table 4

[0066]

[0065] According to the following steps, dark oxidized drying gravure inks (I1 - I23) described in Table 4 were prepared. Weigh the black pigment paste (PP), each transparent white composition (TW0 - TW4), and, if present, the polythiol compounds (TH1 - TH3) independently, and mix them at 2500 rpm for 90 seconds at room temperature using a SpeedMixer (registered trademark) (DAC 150 SP of Hauschild Engineering), and The step of independently adding the desiccant mixtures (D1 to D4) to the dispersion paste obtained in the previous step and further mixing at 2500 rpm for 3 minutes using a SpeedMixer® (DAC 150 SP from Hauschild Engineering).

[0067]

[0066] The viscosities of the dark oxidation drying gravure inks (I1 to I23) were independently measured using a Haake Roto Visco RV1 rotational rheometer using a cone plate with a diameter of 20 mm and a geometry of 0.5° at a shear rate of 1000 s -1 and a temperature of 40 °C.

[0068] B. Preparation and set-off characteristics of gravure printing samples (E1 to E18 and C1 to C23) (Tables 6A to 6D)

[0067] The dark oxidation drying gravure inks (I1 to I23) thus obtained were independently applied by hand using an Ormag gravure proof press. Gravure printing samples (E1 to E18 and C1 to C23) were prepared using a gravure engraved printing plate, and the plate included a series of "U" type engravings with various depths (about 20 μm to about 100 μm) and widths (about 60 μm to about 500 μm) to mimic, for example, the gravure printing features on banknotes.

[0069]

[0068] Using a polymer roller, the gravure engraved printing plate was independently inked with each of the dark oxidation drying gravure inks (step a)), and the plate had a printing plate temperature of 35 °C to 80 °C as shown in Tables 6A to 6D.

[0070]

[0069] Following step a), the excess ink was manually wiped off the printing plate with paper, leaving the ink only in the engraved areas (step b)).

[0071]

[0070] Following step b), the dark oxidation drying gravure ink was independently applied in the form of security features onto a blank sheet of cotton credit paper (Louisenthal) (step c)).

[0072]

[0071] Following step c), the applied ink was dried independently in the presence of air to form a security feature (step d)).

[0073]

[0072] The total residence time of the ink (including inking, wiping off excess ink, and ink transfer) was about 15 seconds. Laboratory gravure presses were used to expose dark oxidation drying gravure ink to a gravure engraved printing plate for about 15 seconds to prepare samples (E1 - E18 and C1 - C23), but the industrial process is much shorter and typically involves exposing the oxidation drying gravure ink to the gravure engraved printing plate for less than 1 second.

[0074]

[0073] For each gravure printed sample, six samples were printed.

[0075]

[0074] Immediately after the printing process, the printed substrates were stacked to form a laminate with a blank sheet sandwiched between the substrates. This laminate was placed between two glass plates and maintained at 22 °C and 50% RH (relative humidity) under a pressure of 3 kg for 24 hours to mimic a laminate of 1500 printed substrates. The printed substrates were then removed from the laminate, and the blank sheets corresponding to each printed substrate were evaluated for set - off characteristics according to the following procedure. i. A series of blank sheets corresponding to various levels of set - off obtained in the same way were classified by a person skilled in the art to design a visual scale with values from 1 to 12, where "1" corresponds to the maximum set - off (i.e., all gravure lines are recorded on the blank sheet), "12" corresponds to the minimum set - off (i.e., little ink is transferred to the blank sheet), and one sample corresponds to one value on the visual scale; ii. Blank sheets of the same series were analyzed at the pixel level to obtain a correlation curve between the values of the visual scale and the number of transferred pixels due to the offset. Samples were scanned at 600 dpi using an Epson Perfection V500 scanner to obtain images, which were then analyzed using Photoshop CC. The absolute number of transferred pixels was measured using a histogram and expressed as a percentage of the transferred pixels compared to a sample with a visual scale value of "1", i.e., the sample showing the maximum offset; iii. A graph shown in Figure 1 (round dots) was defined with the percentage of transferred pixels (relative scale obtained in ii.) on the x-axis and the visual scale on the y-axis. A regression curve (broken line) with the following equation was determined from the experimental data shown in Figure 1: Transferred pixels (interpolated) = 2.295*10 -0.2189*(目視値) (R 2 = 0.9887) iv. According to the equation, for each increment in the value of the visual scale, the number of transferred pixels decreases significantly (by about 40%). Table 5 shows the visual value, the absolute number of transferred pixels, the percentage of transferred pixels determined in b), and the interpolated values obtained from the equation of the regression curve in iii.;

Table 5

[0076]

[0075] The set-off characteristics are shown in Tables 6A to 6D, and the set-off values are shown as visual values ranging from 1 to 12, transferred pixels (estimated in ii.), and the interpolated percentage of transferred pixels (using the formula in iii.).

[0077]

[0076] Since the oxidation-drying gravure inks (I1 to I23) are dark and have a high contrast between the blank sheet and the transferred pixels (both visually and when using a scanner), it has become easy to determine the set-off characteristics.

[0078]

[0077] The determination of set-off was made based on visual values and interpolated transferred pixels: Very low: combination of a visual value exceeding 8 and an interpolated percentage of transferred pixels less than 5% Low: combination of a visual value of 7 to 8 and an interpolated percentage of transferred pixels of 5% to 7% Acceptable: combination of a visual value of 6 to 7 and an interpolated percentage of transferred pixels of 7% to 11% Unacceptable: combination of a visual value less than 6 and an interpolated percentage exceeding 11%

Table 6

[0079]

[0078] As shown in Table 6A, gravure printing samples (C1 to C15) obtained according to a method different from the present invention, that is, a method using a gravure-engraved printing plate heated at a printing plate temperature of less than 45°, or a method using an oxidation-drying gravure ink lacking one or more fusible waxes, or a method using an oxidation-drying gravure ink lacking a polythiol compound, or a method using an oxidation-drying gravure ink lacking one or more waxes and one or more polythiol compounds, exhibit unacceptable set-off characteristics and are not suitable for use in high-performance applications (such as the preparation of security documents).

[0080] In contrast to the comparative examples, the gravure printed samples (E1 - E9) obtained by the method according to the invention, i.e. by using an intaglio engraved printing plate heated to a printing plate temperature of from about 45 °C to about 85 °C, preferably from 50 °C to 80 °C, and an oxidative drying gravure ink containing one or more fusible waxes and one or more polythiol compounds in a total amount of more than 0.5 wt -%, preferably in a total amount of from about 0.75 wt-% to about 2.0 wt-%, show acceptable to very low set-off, making them suitable for high-performance printing applications.

Table 7

[0081] As shown in Table 6B, gravure printed samples (C7 and C16) obtained according to a method different from the present invention, i.e. using an oxidative drying gravure ink lacking one or more polythiol compounds (C7) or containing said one or more polythiol compounds in a total amount of 0.5 wt-% or less (C16), show unacceptable set-off characteristics and are therefore not suitable for use in high-performance applications (such as the preparation of security documents).

[0082] In contrast to the comparative examples, the gravure printed samples (E2, E10, and E11) obtained by the method according to the invention, i.e. by using an intaglio engraved printing plate heated to a printing plate temperature of from about 45 °C to about 85 °C, preferably from 50 °C to 80 °C, and an oxidative drying gravure ink containing one or more fusible waxes and one or more polythiol compounds in a total amount of more than 0.5 wt -%, preferably in a total amount of from about 0.75 wt-% to about 2.0 wt-% (E2, E10, and E11), show acceptable to low set-off, making them suitable for high-performance printing applications.

Table 8

[0083] As shown in Table 6C, gravure printed samples (C7, and C17 - C19) obtained according to a method different from the present invention, i.e., using an oxidative drying gravure ink lacking one or more polythiol compounds, exhibit unacceptable set-off characteristics and are thus not suitable for use in high-performance applications (such as the preparation of security documents).

[0084] In contrast to the comparative examples, gravure printed samples (E2, E12 - E14) obtained by the method according to the present invention, i.e., using i) a gravure engraved printing plate heated at a printing plate temperature of about 45°C to about 85°C, preferably 50°C to 80°C, and ii) an oxidative drying gravure ink containing one or more fusible waxes and one or more polythiol compounds, exhibit acceptable to low set-off and render them suitable for high-performance printing applications.

Table 9

[0085] As shown in Table 6D, gravure printed samples (C20 - C23) obtained according to a method different from the present invention, i.e., using an oxidative drying gravure ink lacking one or more polythiol compounds, exhibit unacceptable set-off characteristics and are thus not suitable for use in high-performance applications (such as the preparation of security documents).

[0086] In contrast to the comparative examples, gravure printed samples (E15 - E18) obtained by the method according to the present invention, i.e., using i) a gravure engraved printing plate heated at a printing plate temperature of about 45°C to about 85°C, preferably 50°C to 80°C, and ii) an oxidative drying gravure ink containing one or more drying agents, one or more fusible waxes, and one or more polythiol compounds, exhibit very low set-off and render them suitable for high-performance printing applications.

[0087] C. Preparation of white / transparent oxidative drying gravure inks (E19 - E22, and C24 - C27)

[0086] The white / transparent oxidative drying gravure ink (I24 - I31, Table 8) used to prepare the printing samples (E19 - E22, and C24 - C27) was prepared by using three kinds of compositions: an ink premix (IP1 - IP2, Table 7) containing a fusible wax (W1), a mixture of desiccants (D1 - D2, Table 2), and a polythiol compound (TH1, Table 3).

[0088]

[0087] To produce the final gravure inks (I24 - 31) as described in Table 8, the polythiol compound (TH1), if present, was added to the ink premix (IP1 - IP2), and then one of the mixtures of desiccants (D1 - D2) was added.

[0089]

[0088] The examples (E19 - E22) were prepared using an ink containing the required amounts of one or more fusible waxes and one or more polythiol compounds according to the method of the present invention.

[0090]

[0089] The comparative examples (C24 - C27) were prepared using an ink containing one or more fusible waxes but lacking one or more polythiol compounds according to the method of the present invention.

Table 10

[0091]

[0090] First, the components described in Table 7 were weighed and mixed with each other at 2500 rpm for 3 minutes at room temperature using a SpeedMixer (registered trademark) (DAC 150 SP of Hauschild Engineering), and then ground three times through a Buhler SDY three - roll mill at pressures of 5, 11, and 11 bar respectively to produce the ink premix (IP1 - IP2).

Table 11

[0092]

[0091] The white / transparent oxidative drying gravure inks (I24 - I31) described in Table 8 were prepared according to the following steps. The ink premixes (IP1 - IP2), and, if present, the polythiol compound (TH1) were independently weighed and mixed at 2500 rpm for 90 seconds at room temperature using a SpeedMixer® (DAC 150 SP from Hauschild Engineering), and The desiccant mixtures (D1 - D2) were independently added to the dispersion paste obtained in the previous step and further mixed at 2500 rpm for 3 minutes using a SpeedMixer® (DAC 150 SP from Hauschild Engineering).

[0093]

[0092] The viscosities of the white / transparent oxidative drying gravure inks (I24 - I31) were independently measured at a shear rate of 1000 s -1 using a Haake Roto Visco RV1 rotational rheometer with a 20 mm diameter cone plate and a 0.5° geometry at a temperature of 40°C.

[0094] D. Preparation of Gravure Print Samples (E19 - E22 and C24 - C27) and Evaluation of Color Characteristics (Tables 9A - 9B)

[0093] The white / transparent oxidative drying gravure inks (I24 - I31) thus obtained were independently applied to black / white Leneta cards (Leneta Inc., Form 2A opacity chart) using a semi - automatic laboratory coater (K101 Control Coater, RK Print) equipped with a coating bar HC4 (nominal thickness 36 μm).

[0095]

[0094] The gravure printing samples (E19 - E22 and C24 - C27) were dried in the dark for 24 hours. After this drying, their L*a*b* values according to CIELAB (1976) were independently recorded on the white part of a Leneta card using a Datacolor spectrophotometer DC 45IR (measurement configuration: 45 / 0°; spectrometer: its own dual channel holographic grating. A 256 - photodiode linear array is used in both the reference and sample channels; light source: full bandwidth LED illumination). These values are represented as L* initial , a* initial , and b* initial in Table 9. All samples were placed in an oven (40 °C, 55% RH) for 14 days, which is approximately equivalent to 2 months of aging at room temperature. The L*a*b* values of all samples were measured again and are represented as L* aged , a* aged , and b* aged in Table 9. The ΔL*, Δa*, Δb*, and ΔE* values shown in Table 9 correspond to the color change after 14 days at 40 °C and 55% RH and were obtained by subtracting the "initial" values from the "aged" values.

[0096]

[0095] The transparency values (shown as ΔTr in Table 9) were obtained by measuring the L*a*b* values in the black part of the Leneta card before aging and comparing them with the L*a*b* values measured in the white part before aging. ΔTr was obtained using the following formula:

Equation

[0097]

[0096]

Table 12

[0098] E. Comparison with offset printing

[0097] The method according to the present invention, i.e., a gravure printing method including step a) of inking an intaglio engraved printing plate with an oxidation-drying gravure ink, wherein the intaglio engraved printing plate is at a printing plate temperature of about 45°C to about 85°C, and the oxidation-drying gravure ink contains i) at least one oxidation-drying varnish, ii) one or more drying agents in a total amount of about 0.01 wt-% to about 10 wt-%, iii) one or more polythiol compounds present in a total amount of more than 0.5 wt-%, preferably in a total amount of about 0.75 wt-% to about 2 wt-%, and iv) one or more fusible waxes present in a total amount of about 1 wt-% to about 10 wt-% was compared with a similar method using an oxidation-drying offset ink containing an equivalent amount of one or more fusible waxes and a polythiol compound of the same chemical formula. Since both inks are highly viscous inks containing high molecular weight compounds (urethane alkyd and phenolic resin) of similar composition and a large amount of pigments / fillers (typically more than 20 wt-%), the oxidation-drying offset ink is equivalent to the gravure ink.

Table 13

[0099]

[0098] Oxidation-drying offset inks (OF1 to OF6) were prepared by manually mixing the components listed in Table 10 other than the mixture of drying agents with a spatula at room temperature. The paste thus obtained was ground three times through a Buhler SDY three-roll mill (the first pass was at a pressure of 6 bar, and the second and third passes were at a pressure of 12 bar). The mixture of drying agents was added to the paste, and about 10 g of the composition thus obtained was mixed at room temperature for 3 minutes at a speed of 2500 rpm in a SpeedMixer® (DAC 150 SP of Hauschild Engineering). The viscosity of ink OF1 was measured using a Haake Roto Visco RV1 rotational rheometer using a cone plate with a diameter of 20 mm and a geometry of 0.5° at a shear rate of 1000 s -1 and a temperature of 40°C.

[0100]

[0099] To mimic the offset printing method, using a Prufbau Multipurpose Printability Tester at a pressure of 1000 N (T = 22 °C, relative humidity = 54%), the oxidative drying offset printing inks (OF1 - OF6) were independently applied as patterns (4.5 cm × 23 cm) on a blank sheet of cotton substrate for credit issuance (Louisenthal). The amount of ink applied was 1 g / m 2 ±0.05 g / m 2 was.

[0101]

[0100] Two series of tests were conducted. In the first series (corresponding to C28 - C33 in Table 11), the printed samples were dried in the dark at 23 °C and 55% RH for 24 hours before performing the set - off evaluation procedure described below. The second series (corresponding to C34 - C39 in Table 11) was first placed in an oven at 65 °C for about 15 seconds and then dried in the dark for 24 hours before performing the set - off evaluation procedure. The method used to obtain the first series (C28 - C33) aimed to mimic the classical offset printing method (without a heating step), while the method including the heating step used to obtain the second series (C34 - C39) was similar to the method of the present invention. Both methods used the oxidative drying offset inks (OF1 - OF6) described in Table 10 instead of oxidative drying gravure inks.

[0102]

[0101] One blank substrate (i.e., an unprinted substrate) was placed on the front of the substrate having the printed and dried layer, and a set - off test was conducted by applying a counter - pressure of 3.4 bar at 65 °C with an ORMAG Intaglio Proof Press to the thus - constructed assembly. The substrate having the printed and dried layer and the blank substrate were separated, and the optical density (OD) of the blank substrate was checked for ink transfer (set - off).

[0103]

[0102] The set - off characteristics are shown in Table 11, and the following formula:

Number

[0104]

[0103] For the purpose of comparing these results as the "transfer pixel (%)" shown above with the results obtained in the gravure printing method, this formula was modified to represent the drying efficiency (%) as the "transfer optical density (%)":

Equation

Table 14

[0105]

[0104] The values obtained by the gravure printing method according to the present invention (Examples E1 to E18, transfer pixels (%)) and the comparative gravure printing method (Examples C1 to C23, transfer pixels (%)) and the values obtained for the samples made by the offset printing method according to the examples (C28 to C39, transfer optical density (%)) cannot be directly compared because the methods are different, but a relative comparison is possible. As shown in Table 11, the addition of one or more fusible waxes and / or one or more polythiol compounds in the oxidative drying offset ink did not affect the drying performance of the ink. In particular, the addition of both one or more fusible waxes and one or more polythiol compounds resulted in a decrease in drying performance or did not significantly improve the performance. The addition of a heating step (65 °C) after offset printing did not significantly improve the drying performance (see C38 vs. C32, or C39 vs. C33).

Claims

1. A method for producing a security feature on a substrate by intaglio printing, comprising: Step a) of inking an intaglio engraved printing plate with an oxidation-drying intaglio ink, wherein the intaglio engraved printing plate is at a printing plate temperature of about 45°C to about 85°C, and the oxidation-drying intaglio ink comprises: i) at least one oxidation-drying varnish; ii) one or more drying agents in a total amount of about 0.01 wt-% to about 10 wt-%; iii) one or more polythiol compounds present in an amount greater than 0.5 wt-%, preferably in a total amount of about 0.75 wt-% to about 2 wt-%; and iv) one or more fusible waxes present in a total amount of about 1 wt-% to about 10 wt-% by weight, based on the total weight of the oxidation-drying intaglio ink, step a); Step b) of wiping off excess oxidation-drying intaglio ink using a paper or tissue wiping system or using a polymeric wiping cylinder, and cleaning the polymeric wiping cylinder with an alkaline aqueous wiping solution in combination with one or more mechanical means; Step c) of transferring the oxidation-drying intaglio ink onto the substrate in the form of the security feature; Step d) of drying the oxidation-drying intaglio ink in the presence of air to form the security feature A method comprising.

2. The method according to claim 1, wherein the intaglio engraved printing plate has a printing plate temperature of about 50°C to about 80°C.

3. The method according to claim 1 or 2, wherein the at least one oxidation-drying varnish is present in the oxidation-drying intaglio ink in an amount of about 10 to about 90 wt-%, by weight based on the total weight of the oxidation-drying intaglio ink.

4. The method according to any one of claims 1 to 3, wherein the one or more polythiol compounds are selected from the group consisting of dithiol compounds, trithiol compounds, tetrathiol compounds, and mixtures thereof.

5. The method according to claim 4, wherein at least one of the dithiol compounds is ethylene glycol bis(3-mercaptopropionate), and / or at least one of the trithiol compounds is tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate, and / or at least one of the tetrathiol compounds is pentaerythritol tetra(3-mercaptopropionate).

6. The method according to any one of claims 1 to 5, wherein the one or more fusible waxes have a melting temperature of about 50 °C to about 120 °C.

7. The method according to claim 6, wherein the one or more waxes are selected from the group consisting of microcrystalline wax, paraffin wax, polyethylene wax, fluorocarbon wax, polytetrafluoroethylene wax, Fischer-Tropsch wax, silicone fluid, beeswax, candelilla wax, montan wax, carnauba wax, rice bran wax, and mixtures thereof.

8. The method according to any one of claims 1 to 7, wherein the one or more desiccants are polyvalent salts containing, as cations (plural possible), cobalt, calcium, copper, zinc, iron, zirconium, manganese, barium, zinc, strontium, lithium, vanadium, and potassium, and, as anions (plural possible), halide, nitrate, sulfate, carboxylate, such as acetate, ethylhexanoate, octanoate, and naphthenate, or acetoacetonate.

9. The method according to claim 8, wherein the oxidative drying gravure ink further comprises one or more desiccants that are metal complexes and / or metal complex salts, preferably manganese complexes, manganese complex salts, vanadium complexes, vanadium complex salts, iron complexes, and iron complex salts.

10. The method according to any one of claims 1 to 9, wherein the oxidative drying gravure ink further comprises one or more fillers or extenders in a total amount of about 0.1 wt-% to about 50 wt-%, based on the total weight of the oxidative drying gravure ink.

11. The method according to claim 10, wherein the one or more fillers or extenders are selected from the group consisting of talc, mica, montmorillonite, bentonite, wollastonite, halloysite, fired clay, china clay, carbonates, silicates, vermiculite, amorphous silica, wood flour, natural fibers, synthetic fibers, and mixtures thereof.

12. The method according to any one of claims 1 to 11, wherein the oxidative drying gravure ink further comprises one or more coloring components selected from the group consisting of optically variable pigments, non-discoloring pigments, dyes, and mixtures thereof, preferably selected from the group consisting of non-discoloring organic pigments, non-discoloring inorganic pigments, and mixtures thereof.

13. The method according to any one of claims 1 to 12, wherein the oxidative drying gravure ink further comprises one or more machine-readable materials selected from the group consisting of magnetic materials, luminescent materials, conductive materials, infrared absorbing materials, and mixtures thereof, and / or one or more forensic taggants.

14. The method according to any one of claims 1 to 13, wherein the substrate is selected from the group consisting of paper or other fibrous materials, paper-containing materials, plastics and polymers, metallized plastics or polymers, composite materials and mixtures, or combinations thereof.

15. A security feature produced by the method according to any one of claims 1 to 14.

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