Intaglio printing method for producing security features made from oxidative dry intaglio inks

Abstract

The present invention relates to the field of processes for producing security features on a substrate by an intaglio printing process comprising: step a) inking an intaglio engraved printing plate with an oxidative dry intaglio ink, the printing plate temperature of the intaglio engraved printing plate being between about 45 DEG C and about 85 DEG C; step b) wiping off any excess of oxidative dry intaglio ink using paper of a tissue wiping system or using a polymeric wiping drum, and cleaning the polymeric wiping drum with an alkaline wiping aqueous solution in combination with one or more mechanical means; a step c) of transferring the oxidatively dried intaglio ink to a substrate in the form of a security feature; and step d) drying the oxidatively dried intaglio ink in the presence of air in order to form the security feature.

Description

Technical Field

[0001] The present invention relates to the field of protecting valuable documents against forgery and illegal copying. In particular, the present invention relates to the field of oxidative drying inks suitable for intaglio printing of valuable documents and intaglio printing methods using oxidative drying inks. Background Art

[0002] With the continuous improvement in the quality of color copies and printouts and attempts to protect security documents from forgery, tampering or illegal copying, it has become conventional practice to introduce various security features into these documents, such as banknotes, valuable documents or cards, transportation tickets or cards, tax banderols and product labels that do not have a reproducible effect.

[0003] Intaglio printing methods refer to printing methods and processes used in particular in the field of value documents. The intaglio printing method is known to be the most consistent and high-quality printing method for producing fine tapered lines and is therefore the printing technology of choice for fine designs in the field of security documents, in particular banknotes and stamps. In particular, one of the notable features of the intaglio printing method is that the layer thickness of the ink transferred to the substrate can be varied from a few micrometers to tens of micrometers by using corresponding shallow or deep engravings on the intaglio printing equipment. As mentioned above, the layer thickness of the intaglio printed security feature thus allows a sufficiently high amount of material on the substrate for its detection and sensing.

[0004] Oxidative drying inks are commonly used in gravure printing processes. The ink is dried by oxidation in the presence of oxygen, particularly in the presence of atmospheric oxygen. During the drying process, the oxygen combines with one or more components of the ink vehicle to convert the ink to a semi-solid or solid state. The process can be accelerated by the use of desiccants, also known in the art as catalysts, siccative agents, desiccatives or dessicators, such as metal salts and the like, and / or by the application of heat treatment.

[0005] Oxidatively drying gravure inks suffer from the so-called "set-off" problem, which is the transfer of ink from one printed sheet to the back of the next printed sheet in a stack, or to the back of a continuous sheet of a web. Although this is a problem that may be encountered in any industrial printing process using oxidatively drying inks, the significant relief of the gravure printed pattern exacerbates the set-off problem. In the case of prior art oxidatively drying gravure inks, the set-off problem has been mitigated primarily by optimizing the ink formulation.

[0006] There remains a need for an intaglio printing process using an oxidatively drying intaglio plate to produce security features that exhibit good drying performance and set-off characteristics, thereby avoiding set-off problems. Summary of the invention

[0007] It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art. This is achieved by providing an oxidatively drying intaglio ink comprising one or more polythiol compounds and one or more fusible waxes.

[0008] A method for producing a security feature on a substrate by an intaglio printing process and the security feature obtained thereby are described herein, the method comprising:

[0009] Step a) inking an intaglio engraved printing plate with an oxidatively drying intaglio ink, said intaglio engraved printing plate being at a printing plate temperature between about 45° C. and about 85° C., said oxidatively drying intaglio ink comprising:

[0010] i) at least one oxidatively drying varnish,

[0011] ii) a total amount of about 0.01 wt % to about 10 wt % of one or more desiccants,

[0012] iii) one or more polythiol compounds present in a total amount greater than 0.5 wt. %, preferably in a total amount of about 0.75 wt. % to about 2 wt. %, and

[0013] iv) one or more meltable waxes present in a total amount of about 1 wt. % to about 10 wt. %,

[0014] The weight percentages are based on the total weight of the oxidatively dried gravure ink;

[0015] Step b) wiping off any excess oxidative drying intaglio ink using a paper or tissue wiping system or using a polymer wiping cylinder and cleaning the polymer wiping cylinder with an alkaline wiping aqueous solution in combination with one or more mechanical means;

[0016] step c) transferring the oxidatively drying intaglio ink to a substrate in the form of a security feature; and

[0017] Step d) drying the oxidatively drying intaglio ink in the presence of air to form the security feature. DETAILED DESCRIPTION

[0018] The following definitions are intended to clarify the meaning of the terms discussed in the specification and defined in the claims.

[0019] As used herein, the indefinite article "a" means one as well as more than one and does not necessarily limit its designated noun to the singular.

[0020] As used herein, the term "about" means that the amount or value in question can be the specified value or some other value nearby. The phrase is intended to convey that similar values ​​within the range of ±5% of the indicated value produce equivalent results or effects according to the present invention.

[0021] As used herein, the term "and / or" or "or / and" means that all or only one of the elements of the group may be present. For example, "A and / or B" should mean "only A, or only B, or both A and B".

[0022] As used herein, the term "at least" is intended to define one or more than one, for example one or two or three.

[0023] The term "security feature" is used to denote an image, pattern or graphical element that can be used for authentication purposes.

[0024] The present invention provides oxidatively drying intaglio inks suitable for intaglio printing processes, in particular for producing security features on value documents.

[0025] Also described herein are security features made by the methods described herein and made from the oxidatively drying intaglio inks described herein and value documents comprising more than one of said security features. Also described herein are the use of the security features described herein for protecting value documents from fraudulent or illegal copying.

[0026] Gravure printing refers to a printing method and process, especially used in the field of printing valuable documents. In the industrial gravure printing process, a rotating steel cylinder carrying a plate engraved with a pattern or image to be printed is supplied with ink by one or more selective inking cylinders (or chablon cylinders), each of which is inked with at least one corresponding color.

[0027] Also described herein are methods for producing security features and security features obtained thereby. The methods described herein comprise the step a): inking an intaglio engraved printing plate with an oxidative drying intaglio ink as described herein, the intaglio engraved printing plate being at a printing plate temperature between about 45° C. and about 85° C. The step a) of inking an intaglio engraved printing plate with an oxidative drying intaglio ink as described herein onto a substrate such as those described herein is typically performed with an intaglio printing plate having areas of different engraving depth and / or width.

[0028] The method further comprises a step b) of wiping off excess oxidative drying intaglio ink from the printing plate using a paper or tissue wiping system or using a polymer wiping roller, and cleaning the polymer wiping roller with an alkaline wiping aqueous solution in combination with one or more mechanical means, the wiping step being performed after step a). Preferably, step b) of wiping off any excess oxidative drying intaglio ink is performed by using a polymer wiping roller, and cleaning the polymer wiping roller with an alkaline wiping aqueous solution in combination with one or more mechanical means, wherein the wiping roller is typically a roller coated with a material that is easy to adhere to the ink, such as, for example, polyvinyl chloride (PVC), wherein the alkaline wiping aqueous solution typically contains caustic soda and a surfactant, such as, for example, sulfated / sulfonated castor oil, and wherein the mechanical means may be one or more brushes and / or pads, such as, for example, Scotch-Brite TM pad).

[0029] The method further comprises a step c) of transferring the oxidatively dried intaglio ink to a substrate in the form of a security feature, the drying step being performed after step b). Step c) comprises bringing a substrate, which may be in sheet form or in roll form, into contact with an intaglio engraved printing plate, so that the oxidatively dried intaglio ink is transferred under pressure from the engraving of the printing plate to the substrate to be printed, thereby forming a security feature on the substrate in the form of a thick relief print pattern. Typically, the security feature is deposited on the substrate under very high pressure.

[0030] The method further comprises a step d) of drying the oxidatively drying intaglio ink as described herein in the presence of air so as to form a layer or coating on the substrate in the form of a security feature as described herein, said drying step d) being performed after step c). Step d) of drying the oxidatively drying intaglio ink as described herein may be performed under hot air, with an infrared source or any combination of hot air and infrared sources so as to reduce the drying time of the ink.

[0031] The oxidative drying gravure ink for the gravure printing method described herein is heated at 40°C for 1000 s. -1 The viscosity of the composites is in the range of about 3 to about 60 Pa s, as measured using a Haake Roto Visco RV1 rotational rheometer using a cone and plate having a diameter of 20 mm and a 0.5° geometry at 1000 s. -1 The oxidative drying gravure ink described herein comprises at least one oxidative drying varnish as described herein, one or more drying agents as described herein, one or more polythiol compounds as described herein, one or more fusible waxes as described herein, and optionally one or more compounds, additives and / or ingredients as described herein.

[0032] The oxidative drying intaglio ink described herein comprises at least one oxidative drying varnish. The term "varnish" is also referred to in the art as a resin, a binder or an ink carrier. The at least one oxidative drying varnish is preferably present in the oxidative drying intaglio ink described herein in an amount of about 10 to about 90 wt %, the weight percentage being based on the total weight of the oxidative drying intaglio ink.

[0033] As is generally known in the art, oxidative drying varnishes are generally polymers comprising unsaturated fatty acid residues, saturated fatty acid residues or mixtures thereof. Preferably, the oxidative drying varnishes described herein comprise unsaturated fatty acid residues to ensure air drying properties. Particularly preferred oxidative drying varnishes are resins comprising unsaturated acid groups, even more preferably resins comprising unsaturated carboxylic acid groups. However, the resins may also comprise saturated fatty acid residues. Preferably, the oxidative drying varnishes described herein comprise acid groups, i.e. the oxidative drying varnishes are selected from acid-modified resins. The oxidative drying varnish 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, polyurethane-modified rosin / phenolic resins, polyurethane-modified rosin esters, polyurethane-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.

[0034] Saturated and unsaturated fatty acid compounds can be obtained from natural and / or artificial sources. Natural sources include animal and / or plant sources. Animal sources can include animal fat, milk fat, fish oil, lard, liver fat, tuna oil, sperm whale oil and / or beef and sheep oil. Plant sources can include oils, such as vegetable oils and / or non-vegetable oils. Examples of vegetable oils include, but are not limited to, bitter melon, Borage, Marigold, rapeseed (canola), castor, Chinese wood, coconut, conifer seeds, corn, cottonseed, dehydrated castor, linseed, grape seeds, jacaranda seeds, linseed oil, palm, palm kernel, peanut, pomegranate seeds, rapeseed, safflower, snake melon, soybean (bean), sunflower, tall, tung oil and wheat germ. Artificial sources include distilled tall oil (tail oil) and / or chemical or biochemical synthesis methods. Suitable fatty acids also include myristic acid (C 14 H 26 O2, CAS No. 544-64-9), palmitic acid (C 16 H 30 O2, CAS No. 373-49-9), oleic acid (C18 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), linoleic 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 (C 20 H 38 O2, CAS No. 29204-02-2), clupanodonic 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. Those fatty acids are usually used in the form of mixtures of fatty acids derived from natural or synthetic oils.

[0035] The oxidative drying gravure ink described herein comprises one or more polythiol compounds, wherein "polythiol compound" refers to a compound having at least 2 thiol functional groups (-SH) per molecule, and is also referred to as a multifunctional thiol 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 2 thiol functional groups), trithiol compounds (i.e., compounds containing 3 thiol functional groups), tetrathiol compounds (i.e., compounds containing 4 thiol functional groups), pentathiol compounds (i.e., compounds containing 5 thiol functional groups), hexathiol compounds (i.e., compounds containing 6 thiol functional groups) and mixtures thereof, more preferably selected from the group consisting of: dithiol compounds, trithiol compounds, tetrathiol compounds and mixtures thereof.

[0036] 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-cyclohexanethiol (CAS No. 3232-05-1), 3-mercapto-cyclohexanethiol (CAS No. 17809-99-3), 2,2'-thiobis(ethanethiol) (CAS No. 3570-55-6), 1-[(2-mercapto- 1,1'-Bis(2-propanethiol)thio]-2-propanethiol (CAS No. 35330-71-3), 1,1'-Bis(2-thiopropanethiol)thio] (CAS No. 35330-70-2), 2,2'-[1,2-ethanediylbis(thio)]bis[ethanethiol] (CAS No. 25423-55-6), 2,2'-[Bis(2,1-ethanediylthio)thio]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, as GDMA is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG); propionic acid, 3-mercapto-, 1,1'-(1,6-hexanediyl) ester (CAS No. 96663-89-7); propionic acid, 3-mercapto-, 1,1'-(1,4-cyclohexanediyl) ester (CAS No. 2227318-91-2); propionic 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, as GDMP is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG). Preferably, the one or more dithiol compounds are esters of mercaptopropionic acid and a polyol, preferably a disubstituted polyol. More preferably, the one or more dithiol compounds are selected from the group consisting of ethylene glycol bis(thioglycolate), 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(3-mercaptopropionate), and even more preferably is ethylene glycol bis(3-mercaptopropionate).

[0037] Preferred examples of the trithiol compound are glyceryl trithioglycolate (CAS No. 14974-53-9), glyceryl trithiopropionate (CAS No. 26424-84-0), trimethylolpropane trimerioacetate (CAS No. 10193-96-1, as TMPMA is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), trimethylolpropane tris-3-mercaptopropionate (CAS No. 33007-83-9, as TMPM is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), ethoxylated trimethylolpropane tris-3-mercaptopropionate (CAS No. 345352-19-4, as ETTMP is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate (CAS No. 36196-44-8, as TEMPIC is commercially available 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 more preferably tris[2-(3-mercaptopropionyloxy)-ethyl]isocyanurate.

[0038] A preferred example of the tetrathiol compound is pentaerythritol tetrakis(thioglycolate) (CAS No. 10193-99-4, as PETMA is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), pentaerythritol tetrakis(3-mercaptopropionate) (CAS No. 7575-23-7, as PETMP and 340 commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG), pentaerythritol tetrakis (4-mercaptobutyrate) (CAS No. 916903-92-9) and polycaprolactone tetrakis (3-mercaptopropionate) (CAS No. 1622079-69-9, as PCL4MP 1350 is commercially available from BOCK Chemische Fabrik GmbH & Co. KG), more preferably pentaerythritol tetrakis(2-mercaptoacetate) and pentaerythritol tetrakis(3-mercaptopropionate), and still more preferably pentaerythritol tetrakis(3-mercaptopropionate).

[0039] A preferred example of a polythiol compound having more than 4 thiol functional groups (-SH) per molecule is dipentaerythritol hexa(3-mercaptopropionate) (CAS No. 25359-71-1, as DiPETMP is commercially available from BRUNO BOCK Chemische Fabrik GmbH & Co. KG).

[0040] The oxidative drying gravure ink described herein preferably comprises one or more polythiol compounds selected from the group consisting of dithiol compounds, trithiol compounds, tetrathiol compounds and mixtures thereof, and more preferably those compounds as 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 tetrakis(3-mercaptopropionate).

[0041] The one or more thiol compounds are present in a total amount greater than about 0.5 wt %, preferably about 0.75 wt % to about 2 wt %, more preferably about 1 wt % to 2 wt %, the weight percentages being based on the total weight of the oxidatively drying gravure ink.

[0042] The oxidative drying gravure ink described herein comprises one or more fusible waxes. In the context of the present invention, one or more fusible waxes refer to waxes or mixtures of waxes having a melting temperature between about 50°C and 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 waxes, paraffin waxes, polyethylene waxes, fluorocarbon waxes, polytetrafluoroethylene waxes, Fischer-Tropsch waxes, silicone oils, beeswax, candelilla waxes, montan waxes, carnauba waxes, rice bran waxes 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 %, the weight percentages being based on the total weight of the oxidative drying gravure ink.

[0043] Oxidative drying safety inks dry by oxidation in the presence of oxygen, particularly in the presence of atmospheric oxygen. During the drying process, the oxygen combines with one or more components of the ink to convert the ink into a solid state. The oxidative drying gravure inks described herein contain one or more desiccants (also referred to in the art as catalysts, siccatives, siccative agents, desiccatives or dessicators) to accelerate the oxidation process. Examples of desiccants include inorganic or organic salts of one or more metals, metal soaps of organic acids, metal complexes and metal complex salts. Suitable salts of one or more metals include salts containing cobalt, calcium, copper, zinc, iron, zirconium, manganese, barium, zinc, strontium, lithium, vanadium and potassium as one or more cations, and halides, nitrates, sulfates, carboxylates such as acetates, ethylhexanoates, octanoates and naphthenates, or acetylacetonates as one or more anions, such as, for example, ethylhexanoates of cobalt, manganese and zirconium. 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, one or more driers for the oxidatively drying intaglio inks 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 %, the weight percentages being based on the total weight of the oxidatively drying intaglio ink.

[0044] According to one embodiment, the oxidative drying intaglio ink described herein is a white, transparent or slightly tinted ink, which allows the preparation of white, transparent or slightly tinted 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 tinted ink. Preferably, the white, transparent or slightly tinted ink contains more than one desiccant, the desiccant being selected from the group consisting of iron compounds, manganese compounds, zirconium compounds and mixtures thereof, wherein the compound may be an inorganic or organic salt of one or more metals, a metal soap of an organic acid, a metal complex and a metal complex salt as described above.

[0045] The oxidative drying gravure ink described herein may further comprise one or more fillers and / or extenders, wherein the fillers and / or extenders are preferably 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 powder), wood flour (sawdust), natural fibers, synthetic fibers (e.g. 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.

[0046] When present, 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 %, the weight percentages being based on the total weight of the oxidatively drying gravure ink.

[0047] The oxidative drying gravure ink described herein may further include more than one surfactant, particularly hydrophilic macromolecular surfactant, such as those described in EP 0 340 163 B1. The role of the optional surfactant is to help wipe off the excess ink present on the printing cylinder immediately before the printing cylinder contacts the substrate. The process of wiping off excess ink is a part of any high-speed industrial gravure printing method and is carried out using a paper towel or paper roll ("calico") or a polymer wiping the cylinder and a clean aqueous solution ("wiping solution"). In this case, an optional surfactant is used to emulsify the excess ink in the cleaning solution. The surfactant can be a nonionic, anionic or cationic and zwitterionic surfactant. In the case of a hydrophilic macromolecular surfactant, the functional group is, for example, a carboxylic acid group or a sulfonic acid group, a hydroxyl group, an ether group, or a primary, secondary, tertiary or quaternary amino group. The acid group can be neutralized with an amine, an alkanolamine (alcanolamines) or preferably an inorganic base or a combination thereof. The primary, secondary and tertiary amino groups can be neutralized with inorganic or organic acids such as sulfonic acid, formic acid, acetic acid, trifluoroacetic acid, etc. Particularly preferred are anionic macromolecular surfactants (AMS), such as those described in EP 2014 729 A1.

[0048] The oxidative drying intaglio ink described herein may be a color constant ink or an optically variable ink. In other words, the oxidative drying intaglio ink may further comprise 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.

[0049] According to one aspect of the present invention, the oxidation drying gravure ink described herein is a color constant ink, and can be white, transparent or slightly colored ink, or can be a colored ink. According to one embodiment, the oxidation drying gravure ink described herein is a white ink with constant color. According to one embodiment, the oxidation drying gravure ink described herein is a transparent ink with constant color. According to one embodiment, the oxidation drying gravure ink described herein is a slightly colored ink with constant color (color constant slightly colored ink). According to one embodiment, the oxidation drying gravure ink described herein is a color constant composition ink, which preferably includes a) more than one dye, and / or b) inorganic pigment, organic pigment or its mixture. The dye suitable for ink is known in the art and is preferably selected from the group comprising the following: reactive dyes, direct dyes, anionic dyes, cationic dyes, acid dyes, basic dyes, food dyes, metal complex dyes, solvent dyes and mixtures thereof. Representative examples of suitable dyes include, but are not limited to, coumarins, cyanines, oxazines, sodium fluorescein, phtalocyanines, indolinocyanines, triphenylmethanes, naphtalocyanines, indolenaphthylphthalide-metal dyes, anthraquinones, anthrapyridones, azo dyes, rhodamines, squarilium dyes, and croconium dyes. Typical examples of dyes suitable for use in the present invention include, but are not limited to, CI 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; CI 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; CI Basic Yellow 13, 28, 65; CI Active Yellow 1, 2, 3, 4, 6, 7, 11, 12, 13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, 42; CI Food Yellow 3, 4; CI Acid Orange 1, 3, 7, 10, 20, 76, 142, 144; CI Basic Orange 1, 2, 59; CI Food Orange 2; CI Orange B; CIAcid 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; CI Basic Red 1, 2, 14, 28; CI 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; CI Active CI Food 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; CI Food Red 1, 7, 9, 14; CI 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;CI Basic Blue 1、3、5、7、8、9、11、55、81;CIDirect 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; CI 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; CI Food Blue 1, 2; CI Acid Green 1, 3, 5, 16, 26, 104; CI Basic Green 1, 4; CI: Food Green 3; CI Acid Violet 9, 17, 90, 102, 121; CI Basic Violet 2, 3, 10, 11, 21; CI Acid Brown 101, 103, 165, 266, 268, 355, 357 , 365, 384; CI Basic Brown 1; CI 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; CI Direct Black 17, 19, 22, 32, 39, 5 CI Reactive Black 1, 3, 4, 5, 6, 8, 9, 10, 12, 13, 14, 18, 31; CI Food Black 2; CI Solvent Yellow 19, CI Solvent Orange 45, CI Solvent Red 8, CI Solvent Green 7, CI Solvent Blue 7, CI Solvent Black 7; CI Disperse Yellow 3, CI Disperse Red 4, 60, CI Disperse Blue 3, and metal azo dyes disclosed in US 5,074,914, US 5,997,622, US 6,001,161, JP 02-080470, JP 62-190272, JP 63-218766. Suitable dyes for use in the present invention may be infrared absorbing dyes or luminescent dyes. When present, one or more dyes for use in the oxidative drying intaglio inks described herein are preferably present in a total amount of about 1 wt % to about 20 wt %, the weight percentages being based on the total weight of the oxidative drying intaglio ink.

[0050] Typical examples of organic and inorganic pigments include, but are not limited to, CI Pigment Yellow 12, CI Pigment Yellow 42, CI Pigment Yellow 93, CI Pigment 109, CI Pigment Yellow 110, CI Pigment Yellow 147, CI Pigment Yellow 173, CI Pigment Orange 34, CI Pigment Orange 48, CI Pigment Orange 49, CI Pigment Orange 61, CI Pigment Orange 71, CI Pigment Orange 73, CI Pigment Red 9, CI Pigment Red 22, CI Pigment Red 23, CI Pigment Red 67, CI Pigment Red 122, CI Pigment Red 13, CI Pigment Red 143, CI Pigment Red 144, CI Pigment Red 145, CI Pigment Red 146, CI Pigment Red 147, CI Pigment Yellow 148, CI Pigment Orange 149, CI Pigment Orange 61, CI Pigment Orange 71, CI Pigment Orange 73, CI Pigment Red 9, CI Pigment Red 22, CI Pigment Red 23, CI Pigment Red 67, CI Pigment Red 122, CI Pigment Red 147, CI Pigment Yellow 173, CI Pigment Orange CI Pigment Red 144, CI Pigment Red 146, CI Pigment Red 170, CI Pigment Red 177, CI Pigment Red 179, CI Pigment Red 185, CI Pigment Red 202, CI Pigment Red 224, CI Pigment Brown 6, CI Pigment Brown 7, CI Pigment Red 242, CI Pigment Red 254, CI Pigment Red 264, CI Pigment Brown 23, CI Pigment Blue 15, CI Pigment Blue 15:3, CI Pigment Blue 60, CI Pigment Violet 19, CI Pigment Violet 23, CI Pigment Violet 32, CI Pigment Violet 37, CI Pigment Green 7, CI Pigment Green 36, CI Pigment Black 7, CI Pigment Black 11, Pigment Black 31, Pigment Black 32, CI Pigment White 4, CI Pigment White 6, CI Pigment White 7, CI Pigment White 21, CI 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, Sulfonated Cadmium Selenide, Zinc Ferrate, Bismuth Vanadate, Prussian Blue, Mixed Metal Oxides, Azo, Azo Methanogen, methine, anthraquinone, phthalocyanine, perinone, perylene, diketopyrrolopyrrole, thioindigo, thiazinindigo, 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 %, the weight percentages being based on the total weight of the oxidatively drying gravure ink.

[0051] For embodiments in which the oxidative drying intaglio ink described herein is a transparent ink, the ink typically does not contain any pigments as those described herein. For embodiments in which the oxidative drying intaglio ink described herein is a white or slightly tinted ink, the ink contains more than one pigment, the pigment preferably being selected from the group consisting of CI Pigment White 4, CI Pigment White 6, CI Pigment White 7, CI Pigment White 21 and CI Pigment White 22.

[0052] According to one aspect of the present invention, the oxidative drying intaglio ink described herein is an optically variable ink and comprises an optically variable pigment or a mixture of different optically variable pigments. The optically variable ink may further comprise more than one pigment constant pigment. The optically variable ink preferably comprises an optically variable pigment or a mixture of different optically variable pigments, wherein 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 intaglio ink described herein in a total amount of between about 5 wt % and about 40 wt %, more preferably in a total amount of between about 10 wt % and about 35 wt %, the weight percentages being based on the total weight of the oxidative drying intaglio ink.

[0053] Suitable thin film interference pigments exhibiting optically variable properties are known to those skilled in the art and are disclosed in US 4,705,300; US 4,705,356; US 4,721,271; US ​​5,084,351; US ​​5,214,530; US 5,281,480; US 5,383,995; US 5,569,535, US 5,571624 and the above-mentioned related documents. When at least a portion of the optically variable pigment consists of a thin film interference pigment, it is preferred that the thin film interference pigment comprises a Fabry-Perot reflector / dielectric / absorber multilayer structure, and more preferably a Fabry-Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure, wherein the absorber layer is partially transmissive and partially reflective, the dielectric layer is transmissive and the reflective layer is reflective of 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, and 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 portion of the optically variable pigment is composed of a thin film interference pigment, it is particularly preferred that the thin film interference pigment comprises a Fabry-Perot absorber / dielectric / reflector / dielectric / absorber multilayer structure consisting of a Cr / MgF2 / Al / MgF2 / Cr multilayer structure.

[0054] The thin film interference pigments described herein are typically manufactured by vacuum depositing the different desired layers onto a roll. After depositing the desired number of layers, the stack of layers is removed from the roll by dissolving the peeling layer in a suitable solvent or by stripping the material from the roll. The resulting material is then broken into flakes that must be further processed by grinding, milling or any appropriate method. The resulting product consists of flat flakes with broken edges, irregular shapes and different aspect ratios.

[0055] Suitable interference coating pigments include, but are not limited to, structures consisting of a substrate of the group consisting of a metal core 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 consisting of a core made of synthetic or natural mica, other phyllosilicates (e.g., talc, kaolin and sericite), glass (e.g., borosilicate), silicon dioxide (SiO2), aluminum oxide (Al2O3), aluminum oxide / hydroxide (boehmite), titanium oxide (TiO2), graphite and mixtures thereof, coated with one or more layers made of metal oxides (e.g., titanium oxide, zirconium oxide, tin oxide, chromium oxide, nickel oxide, copper oxide, iron oxide and iron oxide / hydroxide). The above structures have been described, for example, in Chem. Rev. 99 (1999), G. Pfaff and P. Reynders, pages 1963-1981 and WO 2008 / 083894 A2. Typical examples of these interference coated 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, in particular 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; and titanium oxide cores coated with one or more layers made of iron oxide, iron oxide / hydroxide, chromium oxide, copper oxide, cerium oxide, aluminum oxide, silicon oxide, bismuth vanadate, nickel titanate, cobalt titanate and / or tin oxide doped with antimony, fluorine or indium; aluminum oxide cores coated with one or more layers made of titanium oxide and / or iron oxide.

[0056] The liquid crystal of the cholesteric phase exhibits a molecular order in the form of a helical superstructure perpendicular to its molecular longitudinal axis. The helical superstructure is at the starting point of the periodic refractive index modulation of the entire liquid crystal material, which in turn leads to the selective transmission / reflection of a determined wavelength of light (interference filtering effect). Cholesteric liquid crystal polymers can be obtained by aligning and orienting more than one crosslinking substance (nematic compound) with a chiral phase. The specific situation of the arrangement of the helical molecules makes the cholesteric liquid crystal material exhibit the property of reflecting a circularly polarized light component within a determined wavelength range. The pitch can be adjusted in particular by changing the optional factors including temperature and solvent concentration, by changing the properties of the chiral component and the ratio of the nematic type to the chiral compound. Crosslinking under the influence of UV radiation fixes the pitch in a predetermined state by fixing the desired helical form, so that the color of the resulting cholesteric liquid crystal material no longer depends on external factors such as temperature. The cholesteric liquid crystal material can then be formed into a cholesteric liquid crystal pigment by then crushing the polymer into a desired particle size. Films and pigments made from cholesteric liquid crystal materials and examples of their preparation are disclosed in US 5,211,877; US 5,362,315 and US 6,423,246 and EP 1 213 338 A1; EP 1 046 692 A1 and EP 0 601 483 A1, the disclosures of each of which are incorporated herein by reference.

[0057] The oxidatively drying intaglio ink described herein may further comprise one or more machine readable components, preferably selected from the group consisting of: magnetic materials, luminescent materials, conductive materials, infrared absorbing materials and mixtures thereof.

[0058] The oxidatively drying intaglio inks described herein may further comprise one or more forensic markers and / or one or more taggants.

[0059] The oxidative drying intaglio inks described herein may further comprise one or more additives, including but not limited to compounds and materials for adjusting the physical, rheological and chemical parameters of the composition, such as viscosity, consistency (e.g., anti-settling agents and plasticizers), foaming (e.g., defoamers and degassing agents), UV stability (light stabilizers) and adhesion, etc. The additives described herein may be present in the oxidative drying intaglio inks disclosed herein in amounts and forms known in the art, including in the form of so-called nanomaterials in which at least one dimension of the particles is in the range of 1 to 1000 nm.

[0060] The gravure printing method described herein allows the production of security features on the substrate described herein. The substrate described herein is preferably selected from the group consisting of paper or other fiber materials such as cellulose (including woven and non-woven fiber materials), paper-containing materials, glass, metals, ceramics, plastics and polymers, metallized plastics or polymers, composite materials and mixtures or combinations of two or more thereof. Typical paper, paper-like or other fiber materials are made of various fibers, including but not limited to abaca, cotton, flax, wood pulp and blends thereof. As known to those skilled in the art, cotton and cotton / flax blends are preferably used 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), polyamides (PA), 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), polyesters such as poly(ethylene 2,6-naphthoate) (PEN), and polyvinyl chloride (PVC). For example, in the trademark Those spunbond olefin fibers sold under the trade mark can also be used as substrates. Typical examples of metallized plastics or polymers include the above-mentioned plastic or polymer materials on which metals are deposited continuously or discontinuously on their surfaces. Typical examples of metals include, but are not limited to, aluminum (Al), chromium (Cr), copper (Cu), gold (Au), silver (Ag), alloys thereof, and combinations of two or more of the above-mentioned metals. The metallization of the above-mentioned plastic or polymer materials can be accomplished by an electrodeposition method, a high vacuum coating method, or by a sputtering method. Typical examples of composite materials include, but are not limited to, a multilayer structure or laminate of plastic and / or polymer fibers of paper and at least one plastic or polymer material such as those described above and introduced into a paper-like or fiber material such as those described above. Of course, the substrate may further include additives known to those skilled in the art, such as fillers, sizing agents, brighteners, processing aids, reinforcing or humidifying agents, etc. For the purpose of further improving the level of security and resistance to counterfeiting and illegal reproduction of valuable documents, the substrate may include watermarks, security threads, fibers, planks, luminous compounds, windows, foils, labels, coatings, and combinations thereof.

[0061] Also described herein are methods for producing the oxidative drying intaglio ink described herein and the oxidative drying intaglio ink described herein obtained therefrom. The oxidative drying intaglio ink described herein can be prepared by mixing all ingredients except one or more desiccants and dispersing or grinding them using, for example, a three-roll mill, followed by adding and mixing one or more desiccants. Alternatively, the oxidative drying intaglio ink described herein can be prepared by mixing all ingredients except one or more polythiol compounds and except one or more desiccants and dispersing or grinding them using, for example, a three-roll mill, followed by adding and mixing one or more polythiol compounds, followed by adding and mixing one or more desiccants.

[0062] Also described herein are security features made from the oxidatively drying intaglio inks described herein and made using the methods described herein. Also described herein are the uses of the security features described herein for protecting documents of value from fraud or illegal copying.

[0063] Also described herein are value documents comprising one or more security features made from the oxidative drying intaglio inks described herein such as those described herein. Preferably, the value document is selected from the following: banknotes, contracts, bills, checks, vouchers, tax stamps, agreements, identity documents such as passports, identity cards, visas, driver's licenses, bank cards, credit cards, transactions cards, access documents and cards, admission tickets, public transportation tickets, academic certificates and professional titles. More preferably, the value document is a banknote.

[0064] The security document described herein may further comprise one or more additional layers or coatings below or above the security feature made from the oxidative drying intaglio ink described herein. Should the adhesion between the substrate and the security feature described herein be insufficient, e.g. due to substrate material, surface relief or surface inhomogeneity, an additional layer, coating or primer between the substrate and the security feature may be applied as known to those skilled in the art.

[0065] For the purpose of increasing durability by resistance and cleanliness against contamination or chemicals and thereby increasing the cycle life of the security document, one or more protective layers may be applied over one or more of the security features described herein. When present, one or more protective layers are typically made of a protective varnish, which may be transparent or slightly tinted or light-colored and may have a somewhat glossy finish. The protective varnish may be a radiation-curable composition, a thermal drying composition, or any combination thereof. Preferably, one or more protective layers are made of a radiation-curable, more preferably a UV-Vis curable composition.

[0066] Example

[0067] The invention will now be described in more detail with reference to non-limiting examples. The following examples provide further details of the preparation and use of oxidatively drying intaglio inks for printing security features on substrates by an intaglio printing process. In particular, process examples E1-E22 according to the invention and comparative process examples C1-C27 described thereafter provide further details on the preparation of security features, drying properties and color properties of printed samples obtained by the methods described herein.

[0068] Comparative Examples C28-C39 were prepared according to a comparative offset printing process using the oxidative drying offset inks described in Table 10.

[0069] A. Preparation of oxidative drying gravure ink

[0070] The oxidative drying gravure inks (I1-I23, Table 4) used to prepare the printed samples (E1-E18 and C1-C23, Table 6) were prepared by using 4 compositions: black pigment paste (PP), transparent white composition (TW, Table 1), a mixture of drying agents (D, Table 2) and a polythiol compound (TH, Table 3). When present, the fusible wax (W1-W4) was added during the production of the transparent white composition (TW1-TW4) as described in Table 1. When present, the polythiol compound (TH1-TH3) was added to the dispersed mixture of the transparent white composition (TW0-TW4) and the black pigment paste (PP), and then the mixture of drying agents (D1-D4) was added to produce the final gravure inks (I1-I23) as described in Table 4.

[0071] Examples (E1-E14, Table 6) were prepared according to the method of the present invention and using inks containing the desired amount of one or more fusible waxes and the desired amount of one or more polythiol compounds. Comparative Examples C1, C5, C9 and C13-C15 were prepared according to the comparative method and using inks containing one or more fusible waxes and one or more polythiol compounds. Comparative Examples C2-C4, C6-C8, C10-C12 and C16-C19 were prepared according to the method of the present invention but using inks lacking the desired amount of one or more fusible waxes or lacking the desired amount of one or more polythiol compounds or lacking both.

[0072] Examples (E15-E18, Table 6) were prepared according to the method of the present invention and using inks containing the desired amount of one or more fusible waxes and the desired amount of one or more polythiol compounds. Comparative Examples C20-C23 were prepared according to the comparative method and using inks containing the desired amount of one or more fusible waxes but lacking the desired amount of one or more polythiol compounds.

[0073] The oxidative drying gravure inks (I24-I31, see Table 8) used to prepare the printed samples (E19-E22 and C24-C27) were prepared by using 3 compositions: an ink premix (IP, Table 7), a mixture of drying agents (D, Table 2) and a polythiol compound (TH, Table 3). When present, the polythiol compound (TH1) was added to the ink premix (IP1-IP2) before adding the mixture of drying agents (D1-D2) to produce the final gravure inks (I24-I31) as described in Table 8.

[0074] Examples (E19-E22, Table 9) were prepared according to the method of the present invention and using inks containing the desired amount of one or more fusible waxes and the desired amount of one or more polythiol compounds. Comparative Examples C24-C27 were prepared according to the comparative method and using inks containing the desired amount of one or more fusible waxes but lacking the desired amount of one or more polythiol compounds.

[0075] Black pigment paste (PP) contains:

[0076] 39.1% by weight of polyurethane alkyd resin consisting of Urakyd AL210 Q55 from Synres (polyurethane-modified long oil alkyd resin based on soybean oil)

[0077] 18.4 wt% phenolic resin consisting of 42.4 wt% phenolic modified rosin ester (Bremapal 2035, Kraemer) cooked in 42.4 wt% tung oil (Interfat, CAS No. 8001-20-5) and then diluted with 15.2 wt% n-dodecane (Halterman, CAS No. 112-40-3)

[0078] 13.8 wt. % CI Pigment Black 7, which consists of Special Black 4A from Orion (CAS No. 1333-86-4)

[0079] 28.7 wt% of inorganic filler, which consists of 50(Limestone, CAS No. 1317-65-3, particle size d 50 <2 μm), where

[0080] The ingredients were first weighed and (DAC150SP from Hauschild Engineering) were mixed together at room temperature for 3 minutes at 2500 rpm; subsequently, a grinding step was carried out three times on a Bühler SDY three-roll mill at a pressure of 5, 11 and 11 bar, respectively, to produce a black pigment paste (PP).

[0081]

[0082] The transparent white compositions (TW0-TW4) were prepared by first weighing the ingredients and using (DAC 150SP from Hauschild Engineering) were mixed together (3 minutes at 2500 rpm) and then milled in 3 portions on a Bühler SDY three-roll mill at pressures of 5, 11 and 11 bar respectively.

[0083] Table 2

[0084]

[0085] Table 3

[0086]

[0087]

[0088]

[0089] The dark oxidative drying gravure inks (I1-I23) described in Table 4 were prepared according to the following steps:

[0090] - The black pigment paste (PP), the corresponding transparent white composition (TWO-TW4) and the polythiol compound (TH1-TH3) when present were weighed separately and used (DAC150SP from Hauschild Engineering) at room temperature at 2500 rpm for 90 seconds, and

[0091] - A mixture of desiccants (D1-D4) is added independently to the dispersed paste obtained in the previous step and further (DAC 150SP from Hauschild Engineering) and mixed at 2500 rpm for 3 minutes.

[0092] A Haake Roto Visco RV1 rotational rheometer was used with a cone-plate of 20 mm diameter and 0.5° geometry at 1000 s. -1 The viscosity of the dark oxidative drying gravure inks (I1-I23) was measured independently at a shear rate of 200 Å and a temperature of 40°C.

[0093] B. Preparation and offset properties of gravure printed samples (E1-E18 and C1-C23) (Tables 6A-6D)

[0094] The dark oxidative drying intaglio inks (I1-I23) thus obtained were applied individually manually using an Ormag intaglio test press. Intaglio printing samples (E1-E18 and C1-C23) were prepared using an intaglio engraved printing plate, wherein the plate contained a set of "U" shaped engravings of varying depth (about 20 μm to about 100 μm) and width (about 60 μm to about 500 μm) to simulate the intaglio printing features on banknotes.

[0095] The intaglio engraved printing plates were inked individually with each dark oxidative drying intaglio ink using a polymeric hand roller (step a)), wherein the plates had a printing plate temperature between 35°C and 80°C, as shown in Tables 6A-6D.

[0096] After step a), the excess of said ink is manually wiped off the printing plate with paper, leaving ink only in the engraving (step b)).

[0097] After step b), a dark oxidative drying intaglio ink is applied separately in the form of a security feature on a blank sheet of cotton fiduciary paper (Louisenthal) (step c)).

[0098] After step c), the applied ink is dried independently in the presence of air in order to form the security feature (step d)).

[0099] The total residence time of the ink (including inking, wiping off excess ink and ink transfer) was about 15 seconds. Although the dark oxidative drying gravure ink has been exposed to the gravure engraved printing plate for about 15 seconds to prepare samples (E1-E18 and C1-C23) with a gravure laboratory press, the industrial process will be much shorter and typically involves exposing the oxidative drying gravure ink to the gravure engraved printing plate for a time of typically less than 1 second.

[0100] For each gravure printing sample, 6 samples were printed.

[0101] Immediately after the printing process, the printed substrates were stacked to form a pile with blank paper interlaced between the substrates. The pile was placed between 2 glass plates and kept under a pressure of 3 kg for 24 hours at 22° C. and 50% RH (relative humidity) to simulate a pile of 1500 printed substrates. The printed substrates were then removed from the pile and the offset properties of the blank paper corresponding to each printed substrate were evaluated according to the following procedure:

[0102] i. A series of blank papers obtained in the same way and corresponding to different levels of set-off are classified by a person skilled in the art to design a Visual scale(visual scale), where "1" corresponds to maximum set-off (i.e., all intaglio lines are reported on the blank paper) and "12" corresponds to minimum set-off (i.e., almost no ink is transferred to the blank paper), one sample corresponds to one value of the visual scale;

[0103] ii. Analyze the same series of blank sheets at the pixel level to provide visual scale values ​​and Transfer Number of pixels Correlation curve between. Each sample was scanned at 600 dpi using an Epson Perfection V500 scanner to obtain images analyzed using Photoshop CC. The absolute number of transferred pixels was determined using a histogram and expressed as a percentage of transferred pixels compared to a sample with a visual scale value of "1", which is the sample that exhibited the greatest set-off;

[0104] iii. Use the percentage of transferred pixels on the x-axis (relative ratio obtained in ii.) and a visual scale (circular dots) on the y-axis to establish Figure 1 As shown in the figure. Figure 1 The experimental data shown in Build a regression curve (dashed line) with the following equation:

[0105] Transfer pixels (interpolation) = 2.295*10 -0.2189*(视觉值) (R 2 =0.9887)

[0106] iv. According to the equation, the number of transferred pixels decreases significantly (about 40%) for each increase in the visual scale. Table 5 shows the visual values ​​determined in b), the absolute number of transferred pixels, the percentage of transferred pixels, and the interpolated values ​​obtained from the equation of the regression curve in iii;

[0107] Table 5

[0108]

[0109] *Due to the difference between actual transferred pixels and calculated transferred pixels at high setback, the interpolated percentage of transferred pixels is indicated as "n / a" for visual scale values ​​less than 5 ( Figure 1 The regression curve of

[0110] v. The 6 printed samples (E1-E18 and C1-C23) of each series were evaluated independently by comparing blank sheets with samples of the visual scale described in i. The values ​​provided in Tables 6A-D correspond to the average of 6 visual values, one for each printed sample. The number of transferred pixels was interpolated from the average visual value according to the equation shown in iii.

[0111] "6" as a visual value corresponds to about 11% of transferred pixels and represents an industrially acceptable offset value for the printed gravure sample.

[0112] The pick-up characteristics are provided in Tables 6A-D, where pick-up values ​​are expressed as values ​​between 1 and 12, inclusive. Visual Value , Transfer image white (as estimated in ii.) and Interpolation percentage of transferred pixels (Use the equation in iii.).

[0113] Because the oxidatively drying intaglio inks (I1-I23) are dark in color and the contrast between the blank paper and the transferred pixels is high (both visually and using a scanner), it makes it easy to determine the offset characteristics.

[0114] The appreciation of smearing has been done based on visual values ​​and interpolated transferred pixels:

[0115] - Very Low: A combination of a visual value greater than 8 and an interpolation percentage of less than 5% of transferred pixels

[0116] - Low: A combination of a visual value between 7 and 8 and an interpolation percentage of transferred pixels between 5% and 7%.

[0117] - Acceptable: A combination of a visual value between 6 and 7 and an interpolated percentage of transferred pixels between 7% and 11%

[0118] - Unacceptable: A combination of a visual value less than 6 and an interpolation percentage greater than 11%

[0119] Table 6A

[0120]

[0121] As shown in Table 6A, the gravure printing samples (C1-C15) obtained according to methods other than the present invention, i.e., methods using a gravure engraved printing plate heated at a printing plate temperature below 45°, or methods using an oxidatively dried gravure ink lacking one or more fusible waxes, or methods using an oxidatively dried gravure ink lacking a polythiol compound, or methods using an oxidatively dried gravure ink lacking one or more waxes and lacking one or more polythiol compounds, exhibit unacceptable set-off characteristics and are therefore unsuitable for use in high-end applications such as the preparation of security documents.

[0122] In contrast to the comparative examples, the gravure printing samples (E1-E9) obtained with the method according to the invention, that is, the method of i) using a gravure engraved printing plate heated at a printing plate temperature between about 45°C and about 85°C, preferably between 50°C and 80°C, and ii) using an oxidatively drying gravure ink comprising one or more fusible waxes and one or more polythiol compounds in a total amount of greater than 0.5 wt. %, preferably between about 0.75 wt. % and about 2.0 wt. %, show "acceptable" to "very low" set-off, making them suitable for use in high-end printing applications.

[0123] Table 6B

[0124]

[0125] As shown in Table 6B, the gravure printing samples (C7 and C16) obtained according to methods other than the present invention, i.e., methods using oxidative drying gravure ink lacking one or more polythiol compounds (C7) or methods using oxidative drying gravure ink containing the one or more polythiol compounds in a total amount of not more than 0.5 wt. % (C16), exhibited unacceptable offset characteristics and were therefore not suitable for high-end applications (such as the preparation of security documents).

[0126] In contrast to the comparative examples, the gravure printing samples (E2, E10 and E11) obtained with the method according to the invention exhibit "acceptable" to "low" set-off, making them suitable for high-end printing applications. The method according to the invention is the following method: i) using a gravure engraved printing plate heated at a printing plate temperature between about 45°C and about 85°C, preferably between 50°C and 80°C, and ii) using an oxidatively drying gravure ink (E2, E10 and E11) containing one or more fusible waxes and one or more polythiol compounds in a total amount of greater than 0.5 wt.%, preferably between about 0.75 wt.% and about 2.0 wt.%.

[0127] Table 6C

[0128]

[0129] As shown in Table 6C, the gravure printed samples (C7 and C17-C19) obtained according to methods other than the present invention, i.e., methods using oxidative drying gravure inks lacking one or more polythiol compounds, exhibited unacceptable offset characteristics and were therefore not suitable for high-end applications such as the preparation of security documents.

[0130] In contrast to the comparative examples, the gravure printing samples (E2, E12-E14) obtained with the method according to the invention, i.e. the method of i) using a gravure engraved printing plate heated at a printing plate temperature between about 45°C and about 85°C, preferably between 50°C and 80°C, and ii) using an oxidatively drying gravure ink (E2, E12-E14) comprising one or more fusible waxes and one or more polythiol compounds, showed "acceptable" to "low" set-off, making them suitable for high-end printing applications.

[0131] Table 6D

[0132]

[0133] As shown in Table 6D, gravure printed samples (C20-C23) obtained according to methods other than the present invention, i.e., methods using oxidative drying gravure inks lacking one or more polythiol compounds, exhibited unacceptable offset characteristics and were therefore unsuitable for high-end applications such as the preparation of security documents.

[0134] In contrast to the comparative examples, the gravure printing samples (E15-E18) obtained with the method according to the invention, i.e., the method of i) using a gravure engraved printing plate heated at a printing plate temperature between about 45°C and about 85°C, preferably between 50°C and 80°C, and ii) using an oxidatively dried gravure ink comprising one or more drying agents, one or more fusible waxes and one or more polythiol compounds, exhibit "very low" set-off, making them suitable for high-end printing applications.

[0135] C. Preparation of white / transparent oxidative drying gravure inks (E19-E22 and C24-C27)

[0136] The white / transparent oxidative drying gravure inks (I24-I31, Table 8) used to prepare the printed samples (E19-E22 and C24-C27) were prepared by using 3 compositions: an ink premix (IP1-IP2, Table 7) containing a fusible wax (W1), a mixture of drying agents (D1-D2, Table 2) and a polythiol compound (TH1, Table 3).

[0137] When present, the polythiol compound (TH1) was added to the ink premix (IP1-IP2) before adding one of the mixtures of driers (D1-D2) to produce the final intaglio inks (I24-31) as described in Table 8.

[0138] Examples (E19-E22) were prepared according to the method of the present invention and using inks comprising the desired amounts of one or more fusible waxes and the desired amounts of one or more polythiol compounds.

[0139] Comparative Examples (C24-C27) were prepared according to the method of the present invention and using inks containing one or more fusible waxes but lacking one or more polythiol compounds.

[0140] Table 7

[0141]

[0142] First, weigh the ingredients listed in Table 7 and use (DAC 150SP from Hauschild Engineering) were mixed together at room temperature at 2500 rpm for 3 minutes; subsequently, they were milled on a Bühler SDY three-roll mill in 3 portions at a pressure of 5, 11 and 11 bar, respectively, to produce the ink premix (IP1-IP2).

[0143] Table 8

[0144]

[0145] The white / transparent oxidative drying gravure inks (I24-I31) described in Table 8 were prepared according to the following steps:

[0146] - The ink premix (IP1-IP2) and the polythiol compound (TH1) when present were weighed separately and used (DAC 150SP from Hauschild Engineering) at room temperature at 2500 rpm for 90 seconds, and

[0147] - A mixture of desiccants (D1-D2) is added independently to the dispersed paste obtained in the previous step and further (DAC 150SP from Hauschild Engineering) and mixed at 2500 rpm for 3 minutes.

[0148] A Haake Roto Visco RV1 rotational rheometer was used with a cone-plate of 20 mm diameter and 0.5° geometry at 1000 s. -1 The viscosity of the white / transparent oxidative drying gravure inks (I24-I31) was measured independently at a shear rate of 200 Å and a temperature of 40°C.

[0149] D. Preparation of Gravure Printing Samples (E19-E22 and C24-C27) and Evaluation of Color Properties (Tables 9A-9B)

[0150] The white / transparent oxidative drying gravure inks (I24-I31) thus obtained were applied individually onto black / white Leneta cards (Leneta Inc., forming 2A opacity chart) using a semi-automatic laboratory coater (K101 ControlCoater, RK Print) equipped with a coating bar HC4 (nominal thickness 36 μm).

[0151] The gravure printed samples (E19-E22 and C24-C27) were left to dry in the dark for 24 hours. After this drying, their L*a*b* values ​​according to CIELAB (1976) were recorded independently on the white part of the Leneta card using a spectrophotometer DC 45IR from Datacolor (measurement geometry: 45 / 0°; spectrum analyzer: proprietary dual-channel holographic grating. 256 photodiode linear array is used for both reference and sample channels; light source: full bandwidth LED illumination). These values ​​are respectively expressed in Table 9 as L* 初始 、a* 初始 and b* 初始 All samples were then placed in an oven (40°C, 55% RH) for 14 days, which roughly corresponds to aging for 2 months at room temperature. The L*a*b* values ​​of all samples were measured again and are shown in Table 9 as L* 老化 、a* 老化 and b* 老化 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 are obtained by subtracting the “initial” value from the “aged” value.

[0152] The transparency value (denoted as ΔTr in Table 9) was obtained by measuring the L*a*b* values ​​on the black portion of the Leneta card before aging and comparing them with the L*a*b* values ​​measured on the white portion before aging. ΔTr was obtained using the following equation:

[0153]

[0154] A high ΔTr value indicates high transparency (and therefore low opacity).

[0155] Table 9

[0156]

[0157] E. Comparison with offset printing

[0158] The process according to the invention, i.e. the gravure printing process, is compared with a similar process using an oxidative drying offset ink comprising: equivalent amounts of one or more fusible waxes and polythiol compounds of the same chemical formula, the gravure printing process comprising the following: step a) inking an intaglio engraved printing plate with an oxidative drying intaglio ink, the intaglio engraved printing plate being at a printing plate temperature between about 45° C. and about 85° C., the oxidative drying intaglio ink comprising: i) at least one oxidative drying varnish, ii) a total amount of about 0.01 wt. % to about 10 wt. % of one or more driers, iii) a total amount of greater than 0.5 wt. %, preferably a total amount of about 0.75 wt. % to 2 wt. % of one or more polythiol compounds and iv) a total amount of about 1 wt. % to about 10 wt. % of one or more fusible waxes. Oxidative drying offset inks are similar to gravure inks in that both inks are high viscosity inks containing similar compositions of high molecular weight compounds (such as polyurethane alkyds and phenolic resins, etc.) and large amounts of pigments / fillers (usually in excess of 20 wt. %).

[0159]

[0160] Oxidative drying offset inks (OF1-OF6) were prepared by manually mixing the ingredients listed in Table 10 except the mixture of desiccants with a spatula at room temperature. The paste thus obtained was milled on a Bühler SDY three-roll mill in 3 passes (the first at a pressure of 6 bar, the second and third at a pressure of 12 bar). The mixture of desiccants was added to the paste, and about 10 g of the composition thus obtained was mixed in a The mixture was mixed at 2500 rpm for 3 minutes at room temperature in a DAC150SP from Hauschild Engineering. A Haake Roto Visco RV1 rotational rheometer was used with a cone and plate having a diameter of 20 mm and a geometry of 0.5° at 1000 s. -1 The viscosity of ink OF1 was measured at a shear rate of 1000 Å and a temperature of 40°C.

[0161] For the purpose of simulating the offset printing process, the oxidatively dried offset printing inks (OF1-OF6) were applied individually as patterns (4.5 cm×23 cm) on a blank sheet of trust cotton substrate (Louisenthal) using a Multipurpose Printability Tester from Prüfbau at a pressure of 1000 N (T=22° C., relative humidity=54%). The amount of ink applied was 1 g / m 2 ±0.05g / m 2 .

[0162] Two series of tests were conducted. In the first series (corresponding to C28-C33 in Table 11), the printed samples were placed at 23°C and 55% RH to dry in the dark for 24 hours, and then they were subjected to the sticky evaluation procedure described later. The second series (corresponding to C34-39 in Table 11) was first placed in an oven at 65°C for about 15 seconds, then placed in the dark to dry for 24 hours, and then they were subjected to sticky evaluation. The purpose of the method for obtaining the first series (C28-C33) is to simulate the classical offset printing method (in which no heating step is involved), while the method for obtaining the second series (C34-C39) including a heating step is more similar to the method of the present invention, wherein the method uses the oxidative drying offset ink (OF1-OF6) described in Table 10 instead of the oxidative drying gravure ink.

[0163] The set-off test was performed by placing a piece of blank substrate (i.e. unprinted substrate) on the front side of the substrate bearing the printed and dried layer and by subjecting the assembly thus formed to a counterpressure of 3.4 bar with an ORMAG gravure test press at 65° C. The substrate bearing 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).

[0164] Table 11 provides the offset characteristics and has been evaluated according to the following equation:

[0165]

[0166] in,

[0167] OD is the obtained value,

[0168] OD max is the optical density at maximum fouling and corresponds to 0% drying efficiency,

[0169] OD min is the optical density obtained in the complete absence of set-off and corresponds to a drying efficiency of 100%, Table 1

[0170] Prepare 2 blanks to determine the 2 possible extremes of drying behavior, OD max and OD min ,

[0171] The OD was obtained by measuring the following samples: max , the sample was obtained by back-pressing the fresh ink layer directly after printing,

[0172] OD was measured on samples without printed samples. min ,and

[0173] Optical density values ​​were obtained by GretagMacbeth D19C densitometer (average of 2 measurements).

[0174] For the purpose of comparing these results with the results obtained for the gravure printing process and provided above as "transferred pixels in %", the equation was modified to express the drying efficiency in % as "transferred optical density in %":

[0175]

[0176] Table 11

[0177]

[0178] Although a direct comparison between the values ​​obtained by the gravure printing methods according to embodiments of the present invention (E1-E18, transferred pixels (%)) and the comparative gravure methods (C1-C23, transferred pixels (%)) and the values ​​obtained for samples made by offset printing method embodiments (C28-C39, transferred optical density (%)) is not relevant because the methods are different, 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 to the oxidative drying offset ink does not affect the drying properties of the ink. Specifically, the addition of both one or more fusible waxes and one or more polythiol compounds results in a decrease in the drying properties or does not significantly improve the properties. Adding a heating step (65°C) after offset printing does not significantly improve the drying properties (see C38 vs. C32 or C39 vs. C33).

Claims

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

2. The method of claim 1, wherein the intaglio engraving printing plate has a printing plate temperature between about 50°C and about 80°C.

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

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

7. The method of 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 oil, 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 multivalent salts containing cobalt, calcium, copper, zinc, iron, zirconium, manganese, barium, zinc, strontium, lithium, vanadium and potassium as one or more cations and halide, nitrate, sulfate, carboxylate such as acetate, ethylhexanoate, octanoate and naphthenate or acetylacetonate as one or more anions.

9. The method according to claim 8, wherein the oxidative drying intaglio ink further comprises one or more drying agents, the drying agents being 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 oxidatively drying intaglio ink further comprises one or more fillers or extenders in a total amount of about 0.1 wt. % to about 50 wt. %, the weight percentages being based on the total weight of the oxidatively drying intaglio ink.

11. The method of claim 10, wherein the one or more fillers or extenders are selected from the group consisting of talc, mica, montmorillonite, bentonite, wollastonite, halloysite, calcined 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 oxidatively drying intaglio ink further comprises one or more coloring components selected from the group consisting of optically variable pigments, color constant pigments, dyes and mixtures thereof, preferably selected from the group consisting of color constant organic pigments, color constant inorganic pigments and mixtures thereof.

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

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 made by the method of any one of claims 1 to 14.

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