WO2011113944A1

WO2011113944A1 - Ink composition for liquid jet printing

Info

Publication number: WO2011113944A1
Application number: PCT/EP2011/054162
Authority: WO
Inventors: Pierre De Saint-Romain
Original assignee: Markem-Imaje
Priority date: 2010-03-19
Filing date: 2011-03-18
Publication date: 2011-09-22
Also published as: FR2957605A1; FR2957605B1

Abstract

A non-aqueous ink composition for liquid jet printing comprising a carrier, vehicle, comprising one or more organic solvent(s) liquid at room temperature; one or more dye(s) and/or pigment(s); a binder, comprising at least one binding resin consisting of particles of at least cross-linked polymer obtained by polymerization in an aqueous emulsion of at least one monomer selected from monomers with a single unsaturated carbon-carbon double bond of the ethylenic type, and of at least one cross-linking agent. A method for marking substrates, supports or objects by projection on these substrates, supports or objects of said ink composition by a liquid jet printing technique. A notably flexible substrate, support or object provided with a marking obtained by drying and/or absorption of said composition.

Description

INK COMPOSITION FOR LIQUID JET PRINTING

DESCRIPTION

The invention relates to an ink composition for marking supports and objects of all kinds, the properties of which are particularly well adapted to marking or printing with a liquid jet, so-called « ink jet » printing or marking of a very large variety of supports, substrates and objects, especially flexible supports, substrates and objects.

Ink jet printing is a well-known technique, which allows printing, marking or decoration of all kinds of objects, at a high rate, and without any contact of these objects with the printing device, of messages variable at will, such as bar codes, sell-by dates, etc. and this even on non-planar supports.

The ink jet printing systems are divided in two major types: « drop on demand » (DOD) or « continuous jet » (CIJ) .

The « drop on demand » jet projection may be accomplished with a so-called « bubble » ink jet, with a so-called « piezoelectric » jet, by a so-called « valve » ink jet or finally by a so-called « hot melt » ink jet or phase change ink jet.

In the case of the bubble ink jet, the ink is vaporized in the vicinity of the nozzle and this vaporization causes ejection of the small amount of ink located between the resistor which vaporizes the ink and the nozzle. In the case of the piezoelectric ink jet, a sudden change in pressure caused by an actuator set into motion by the electric excitation of a piezoelectric crystal or ceramic and located in the vicinity of the nozzle, causes ejection of an ink drop.

In the case of the « hot melt » ink jet, the ink is without any solvent and it is brought to beyond its melting point.

Drop on demand printing may therefore be accomplished at room temperature, this is the case of the piezoelectric ink jet, of the valve ink jet or of the bubble ink jet, or at a high temperature for example at about 60-130°C, this is the case of the so-called « hot melt » (HM) ink jet or phase change ink j et .

Projection with a deflected continuous jet consists of sending ink under pressure into a cavity containing a piezoelectric crystal, from which the ink escapes through an orifice (nozzle) as a jet. The piezoelectric crystal, vibrating at a determined frequency, causes pressure perturbations in the ink jet, which oscillates and gradually breaks into spherical drops or droplets. An electrode, a so-called « charge electrode », placed on the path of the jet, there where it breaks, allows these drops to receive an electrostatic charge, if the ink is conducting. The thereby charged drops are deflected in an electric field and allow printing.

For all the types of ink jet technology, the viscosity of the inks is very low at the projection temperature, typically from 1-20 cPs and these technologies may therefore be described as low viscosity ink deposition technologies. The ink jet projection provides contactless marking at high displacement rates on not necessarily planar objects and with the possibility of changing the message at will.

Ink compositions, suitable for projection by a jet, have to meet a certain number of criteria inherent to this technique, relating i.a. to viscosity, solubility in a solvent for cleaning, compatibility of the ingredients, proper wetting of the supports to be marked, etc., and electric conductivity in the case of the deflected continuous jet.

Further, these inks have to dry rapidly, be capable of flowing or remaining immobile in the vicinity of the nozzle without blocking it, with great orientation stability of the jet while allowing easy cleaning of the printing head.

The ingredients which make up present inks, for the ink jet of the deflected continuous ink jet type, are organic or inorganic, mineral products; these are dyeing materials, dyestuffs, such as dyes or pigments, resins or binders, in one or more solvent (s) that is (are) more or less volatile, or in water, and optionally one or several salt(s) providing conductivity, as well as various additives.

The ingredients which make up present inks for the ink jet of the drop on demand (DOD) type are also organic or inorganic, mineral products; dyes (coloring agents) or pigments, resins or binders, in one or more solvent (s) that is (are) more or less volatile, or in water, in proportions other than those of inks for deflected continuous ink jet, but without the requirement of electric conductivity.

The solvent of inks for the ink jet, except for inks for the « Hot Melt » ink jet, most frequently consists of a mixture comprising a majority amount of volatile and not very viscous solvents on the one hand in order to allow very rapid drying of the markings and to adjust the viscosity to the desired value, for example from 1 to 10 mPa.s and, of more viscous and less volatile solvents with slower drying in a smaller amount on the other hand in order to avoid drying of the ink in the nozzle during the stopping phases of the printing device (see patents or patent applications US-A-4, 155, 767, WO-A-92 14794, WO-A-92 14795 and US-A-4, 260, 531) .

The volatile solvents most often used are alcohols, ketones or esters of low molecular weight, as this is indicated in patents US-A-4, 567, 213, and US-A-5, 637, 139. Among these solvents, mention may essentially be made of methanol, ethanol, 1- and 2-propanol, acetone, methyl ethyl ketone (MEK) , methyl isobutyl ketone, ethyl acetate and tetrahydrofurane .

The additives comprise:

- plasticizers which soften the film of dry ink, which may improve adherence and cohesion of the ink on the marked support,

- dispersants which allow dispersion of the pigments. Such dispersants stabilize the pigments by a steric effect and/or by an electrostatic effect depending on whether they are ionizable or not, and depending on the polarity of the solvent, - agents which inhibit corrosion induced par certain salts like chlorides which provide conductivity (see documents EP-A-0 510 752, US-A-5, 102, 458) ;

- additives which protect the ink against proliferations of bacteria and of other micro-organisms: these are biocides, bactericides, fungicides and other agents, particularly useful in inks containing water,

- pH regulating buffers (see EP-A-0 735 120), - anti-foam agents.

The inks for ink jet may also comprise surfactants, tensides, or surface-active agents which modify the wetting power or penetrating power of the ink (cf. patent US-5, 395, 431) , in particular those which modify or regulate the static or dynamic surface tension such as Fluorad FC 430 from 3M. Such products equalize the size of the impacts of the drops. By means of them, the impacts of the drops all have the same diameter regardless of the nature, the cleanliness or evenness of the support.

The additives also comprise, in the case of inks for printing with a deflected continuous ink jet, optionally one or more conductivity salts.

The optional conductivity salt(s) provide (s) the ink with the conductivity required for electrostatic deviation. On this subject, reference may be made to document US-A-4 , 465 , 800. However, it may be noted that in certain cases the dyes also provide already sufficient conductivity to the ink so that there is no need to add a conductivity salt. The coloring materials, dyestuffs, are called « dyes or pigments », depending on whether they are respectively soluble or insoluble in the solvent used.

Pigments, by nature insoluble, are therefore dispersed and may be opaque or not. They provide the ink with its color, its opacity or particular optical properties, such as fluorescence (see patents or patent applications US-A-4, 153, 593, US-A-4 , 756, 758 ;

US-A-4, 880, 465; EP-A-0 289 141, US-A-5, 395, 432 ; GB-A-2, 298, 713) . In certain cases, the dyes also themselves provide sufficient conductivity to the ink so that there is no need to add a conductivity salt. The dyes known under the name of C.I. Solvent Black 27, 29, 35 and 45 are in this case.

The binder (s) or resin (s) is (are) generally mostly solid and polymeric compound (s) and their selection is dictated by their solubility in the selected solvents, by their compatibility with the dyes and with the other additives, their capability of allowing proper electrostatic charging of the drops but also depending on the properties which they provide to the ink film, once they are dry (see patents or patent applications US-A-4, 834, 799; GB-A-2 , 286 , 402 , US-A-5 , 594 , 044 ; US-A- 5,316,575; WO-A-96/23844 ; WO-A- 95 /29287 ) .

Their primary function is to provide adherence of the ink on a maximum of supports or on specific supports, for example non-porous supports. They also allow the ink to be provided with the adequate viscosity for forming drops from the jet and they provide to the obtained marking, the essential of its properties of resistance to physical and/or chemical aggressions such as resistance to friction and more generally to abrasion.

The polymers used with the organic solvents are synthetic or natural, these may either be linear polymers, such as rosin resins, shellac, resins of the acrylic, methacrylic, styrenic, vinyl, cellulosic, and phenolic type, polyamides, polyurethanes , melamines, or further polyesters or branched polymers such as dendrimers (see US-B2-6, 221, 933) .

Weakly cross-linked polymers cannot obviously be used since they give rise to gels and not to solutions.

Completely cross-linked polymers such as rubbers are intrinsically insoluble in solvents and at best swell in solvents. On the other hand, pre-polymers which are cross-linkable by radiations, for example ultraviolet rays, electron beams, are used and are subject to cross-linking after deposition on the support .

For formulations in an aqueous phase, the polymers are either soluble linear polymers, or dispersions also called latexes. The polymers of these dispersions may be linear or cross-linkable during drying.

The polymers or resins used in j et-proj ectable inks are generally polymers of relatively low molecular mass for two essential reasons:

if the molecular masses of the polymers or resins are too high, the viscosity provided by these polymers or resins is very large and their amount is very small, and especially too small for properly coating the coloring materials, dyestuffs, of the inks. This is true for all ink jet technologies. if the molecular masses of the polymers or resins are too high, the electrostatic charges of the drops are not stable and the printing is of poor quality, or even impossible, because the separation of the drops upon their charging is not facilitated and is unstable. This is true for the ink jet of the deflected continuous jet type.

Moreover, it is generally known that the marking of flexible or even very flexible supports, substrates, such as rubber substrates, supports, or plastic films, poses a problem, which is particularly difficult to solve .

The adherence of the inks on such supports is difficult since the ink should be as flexible as the support in order to adhere thereto. By limiting the molecular masses of the polymers used as a binder of the inks, it is not possible to plasticize them sufficiently without risking their being made tacky and very weakly resistant to friction or abrasion. Among the polymers soluble in organic solvents, only polymers such as PVC may be strongly plasticized without becoming tacky, but such chlorinated polymers are in the process of being banned.

Considering the foregoing, there is therefore a need for an ink composition which may be projected by all technologies for depositing low viscosity ink, and which allows marking of all the flexible, or even very flexible supports, such as plastic films and rubbers at room temperature, and even more at a low temperature, i.e. at a temperature generally from -30°C to +10°C. There still exists a non-satisfied need for an ink composition suitable for ink jet printing, whether this be by drop on demand or by a continuous jet, which gives markings having good adherence and good resistance to chemical aggressions, especially good resistance to water, good resistance to abrasion, to folding, to friction, rubbing or further to creasing, rumpling, in particular on flexible or even very flexible supports, such as plastic films or rubbery supports.

There also exists a need for an ink composition for liquid jet printing, which does not contain, especially in the binder, components, such as polymers, banned or in the process of being banned.

This ink composition should further have all the customarily required properties of inks for inkjet printers, for example inks using the technique of the continuous jet: viscosity, resistivity, etc. The ink should have both the property of drying rapidly, of not obstructing the nozzles and of thereby allowing rapid starting even after stopping for a long period.

With the ink, it should further be possible to mark at a high rate, objects of all kinds, even slightly porous objects, while always providing a print or marking of excellent quality and regularity.

The goal of the invention is to provide an ink composition for liquid jet printing which i.a. meets the needs and requirements listed above.

The goal of the invention is further to provide an ink composition for liquid jet printing which does not have the drawbacks, defects, limitations and disadvantages of the compositions of the prior art and which provides a solution to the problems of the compositions of the prior art.

This goal and still others are achieved, according to the invention, by a non-aqueous ink composition for liquid jet printing comprising:

a vehicle, carrier, comprising, preferably consisting of, one or more organic solvent (s) liquid at room temperature;

- one or more dye(s) (coloring agent (s) ) and/or pigment ( s ) ;

- a binder, comprising at least one binding resin consisting of particles of at least one entirely cross-linked polymer, having a cross-linking level, degree, of 100%, obtained by polymerization in an aqueous emulsion of at least one monomer selected from monomers with a single unsaturated carbon-carbon double bond of the ethylenic type, and of at least one cross- linking agent.

By room temperature is generally meant a temperature from 5 to 30°C, preferably from 10 to 25°C, still preferably from 15 to 24°C, better from 20 to 23°C.

It is well understood that the ink is liquid at atmospheric pressure.

Advantageously, the binder may comprise at least 10% by weight, preferably at least 50% by weight of said binding resin consisting of particles of at least one cross-linked polymer.

Advantageously, the binder may consist of (be composed of) said at least one binding resin consisting of (composed of) particles of at least one cross-linked polymer .

Said at least one polymer is entirely cross-linked, has a cross-linking level of 100%.

By entirely cross-linked polymer, having a cross-linking level of 100%, is generally meant in the sense of the invention that there is no longer any free polymer chain which is not bound to another chain.

The particles may be particles with a « core » structure.

Each particle with a « core » structure consists of (is composed of) a single, entirely cross-linked polymer, with a cross-linking level of 100%, and each particle only consists of one single polymer molecule.

Or else, the particles may be particles with a

« core/shell » or « core/skin » structure, the core and the shell consisting respectively of a first polymer and a second polymer, different from each other, each of these polymers being entirely cross-linked.

The first polymer, which constitutes the core of the particle, and the second polymer, which constitutes the shell of the particle, are both 100% cross-linked.

The core of the particle may consist of one single molecule of the first polymer and the shell of the particle may consist of one single molecule of the second polymer.

Or else the core and the shell may also only consist together of one single and same molecule.

Advantageously, the core of the particles may consist of a first polymer with a glass transition temperature of less than 0°C, and the shell of the particles may consist of a second polymer with a glass transition temperature above 20 °C; the first and the second polymers having a cross-linking level of 100%.

Advantageously, the particles may have a spherical or spheroidal shape.

Advantageously, the particles with a « core » structure may have a size, defined by their largest dimension, for example, their diameter, of less than or equal to 1 ym, preferably from 25 nm to 1 ym.

The particles with a « core/shell » structure may have a core size (diameter) of less than or equal to 1 ym, preferably from 25 nm to 1 ym, and a shell thickness from 0 to 80 nm.

Advantageously, the molecular mass of each particle is from 4.10^s to 2.10⁹ daltons, preferably from 4.10⁷ to 4.10⁸ daltons.

These molecular mass ranges are valid both for particles with « core » structure and for particles with a « core/shell » structure.

Advantageously, the particles both in the case of particles with a « core » structure and in the case of particles with a « core/shell » structure may have a polydispersity index « PDI », measured by quasi-elastic light scattering, of less than 0.5, preferably less than 0.2.

In fact, it may generally be considered that the particles obtained by polymerization in an emulsion are perfectly spherical (or almost spherical) , and strictly of the same size. Advantageously, the particles have a volume swelling ratio from 1.2 to 10, preferably from 1.5 to 5, and still preferably from 2 to 4.

These swelling ratios are valid both for particles with a « core » structure and for particles with a « core/shell » structure.

The ink composition according to the invention is fundamentally distinguished from ink compositions for liquid jet printing of the prior art in that this composition is a non-aqueous composition and in that it uses a specific binder comprising at least one specific binding resin consisting of particles of at least one entirely cross-linked polymer obtained by polymerization in an aqueous emulsion of at least one monomer specifically selected from monomers with a single unsaturated carbon-carbon double bond of the ethylenic type, the cross-linking being generally achieved by copolymerization of a monomer with more than one unsaturated carbon-carbon bond of the ethylenic type.

No prior art document describes or suggests an ink composition having the whole of the specific features of the ink composition according to the invention.

In particular, no prior art document describes or suggests the use of such particles of entirely cross- linked polymers made by emulsion polymerization in an aqueous medium, in non-aqueous ink compositions for ink jet printing wherein said particles are dispersed in an organic medium, and especially in a substantially and even exclusively organic carrier. The invention is especially based on the surprising finding that polymers synthesized by emulsion polymerization and entirely cross-linked may be used as binders in inks for ink jet printing, and improve cohesion, flexibility, resistance to abrasion or to friction of markings and prints made with inks on flexible or rubbery supports.

The ink compositions according to the invention do not have the drawbacks of the compositions of the prior art and provide a solution to the problems of the compositions of the prior art.

By polymerization in an aqueous emulsion, is generally meant polyaddition of monomers with an unsaturated carbon-carbon double bond of the ethylenic type, especially of vinyl or (meth) acrylic monomers, accomplished in an aqueous phase, generally in the presence of soaps, and leading to the obtaining of aqueous dispersions of particles with a diameter generally comprised between a few nanometers, for example 25 nm and about one micron.

The emulsion polymerization is a very common polymerization technique, with which it is possible to obtain polymers of all kinds, either rigid or flexible, such as rubbers, and with very diverse molecular masses. A large number of publications describe this emulsion polymerization method and all its alternatives. In this respect, mention may especially be made of the following documents:

- « Textbook of Polymer Science » of Billmeyer, Jr. F. W., New York, 1984; - « Emulsion Polymerization and Emulsion Polymers » of Peter A. Lovell and Mohamed S. El-Aasser, Wiley, March 1997;

- « Chemistry and Technology of Emulsion Polymerization » by A.M. van Herk, Wiley, September

2005;

- « Emulsion polymer technology » by Robert D. Athey; - « Emulsion Polymerization Theory and Practice » D. C. Blackley, Appl . Science Publn. Ltd., 1975;

- « Polymer Latexes: Preparation, Characterization, and Applications », E. S. Daniels and M. S. El-Aasser, eds . , ACS, 1992.

The emulsion polymerization technique produces polymers as individual particles with submicron size and dispersed in an aqueous phase. These dispersions sometimes called emulsions or further latexes, may be used as such in formulations of paints, inks or aqueous adhesives .

Precipitation by destabilization of these particles allows the polymer to be recovered as a solid. This is especially the case of PVC, of many styrene-butadiene rubbers « SBR », acrylonitrile-butadiene rubbers « NBR », of resins for paints with a solvent or toners for copy machines.

When the monomers used are monofunctional , the obtained polymers are linear and their molecular mass may be adjusted at will by means of polymerization transfer agents.

When polyfunctional monomers such as for example divinylbenzene or diacrylates, are added to monofunctional monomers, each particle of the dispersion may be cross-linked at will depending on the ratios of the monomers.

This is especially the case of certain rubbers used as polymeric and non-migrating plasticizers for PVC or as processing aids or impact modifiers in the manufacturing of plastic materials.

Such cross-linked polymers are also called « microgels », because the extent of their cross-linked structure is limited to each of the particles of dimensions of the order of one micron or less than one micron .

When different monomers are added during polymerization, each particle may consist of a « core » and of a « skin » or « shell » in different polymers but according to the invention, the polymers are each 100% cross-linked. Such particles are thus called « core/shell » particles.

If these cross-linked polymers are put into the presence of adequate solvents, they are not solubilized, strictly speaking, but they swell depending on their cross-linking level, degree, and retain their structure of elementary particles and disperse in the solvent medium. Such dispersions have particular rheological, flow, behaviors and are especially used as thickeners in the formulations of paint for masonry. An example of this rheological, flow, behavior is given in the article of the Journal of Colloid and Interface Science, Vol. 33, No.l, November 1989. The article of J.F. Tassin et al . published in Progress in Organic Coatings 26, 1995, pages 239-250, describes the structure and rheological, flow, properties of such microgels and specifies their use as a rheological, flow, additive in organic coatings.

The article of Shinichi Ishikura published in Polymer News 1997, Vol. 22, pages 344-351, also suggests the use of microgels as a rheological, flow additive in paints.

However, the use of microgels as a binder in inks, the vehicle, carrier of said inks consisting of organic solvents, liquid at room temperature has never been described nor suggested in the prior art.

In particular, it has been shown, according to the invention, in particular that in a totally surprising way, while their rheological, flow, behavior is strongly pseudo-plastic in a concentrated solution, the microgels consisting of particles of cross-linked polymers may advantageously be used, preferably under certain conditions explained below, in ink formulations for ink jet printing, the rheological, flow behavior of which is essentially Newtonian .

Because of the total cross-linking, 100 % cross linking of each particle of the microgel, each particle only consists of one single molecule wherein all the atoms are bound to each other as a single entity. It may be calculated that the molecular mass of such particles is equal to:

M = Na.m wherein Na is the Avogadro number, and m is the actual mass of the particle. That is M = Na.p.Il.D³/6 wherein D is the diameter of the particles and p is their density. Thus particles with a density of 1 g/m³ and a diameter of 0.025 ym will have a molecular mass of 4.9 10^s daltons, particles with a diameter of 0.05 ym will have a molecular mass of 39.5 10^s daltons, particles with a diameter of 0.1 ym will have a molecular mass of 314 10^s daltons, while polymers, which may be used in inks for ink jet printing generally have molecular masses of much less than 100,000 Da.

Depending on the type of polymer, the acceptable maximum molecular masses may be different.

In spite of these enormous molecular masses, because of their cross-linked structure and possibly their spherical shape, the dispersions in organic solvents or organic compounds (the inks according to the invention may be considered as dispersions of polymeric particles swollen by the solvent) of cross- linked particles as described above, surprisingly have low viscosities at relatively high concentrations, which surprisingly makes them quite capable of being projected by a jet.

When these particles are dispersed in a good solvent, these particles are swollen by the solvent up to a certain level, which depends on the cross-linking level and on the average distance between the cross-linking points. A good solvent is intended to mean a solvent capable of entirely dissolving a non-cross-linked polymer of same composition.

This swelling ratio may be estimated by measuring the size of the particles in water, as they are at the end of polymerization, on the one hand, and in the relevant solvent on the other hand. The ratio of the diameters gives a diameter swelling ratio and the cube of this number is the volume cross-linking ratio.

The sizes of the particles are easily measured by elastic scattering of light (also called « photon correlation spectroscopy ») , for example by means of the granulometer Nano-S made by Malvern . This apparatus conventionally gives a hydrodynamic diameter called Z-average. The ratio of the Z-average in the solvent to that in water will be the size swelling rate .

When the measured swelling ratio is too high, it is possible that the particles should not be entirely cross-linked in a single molecule, but that non-cross-linked molecules may exist and escape from the partly cross-linked particles during the swelling by the solvent. These free molecules of very high molecular mass are detrimental to the projection by an ink jet and significantly contribute to increasing the viscosity of the solutions.

When the swelling ratio is too low, the particles risk being not kept sufficiently suspended in the low viscosity solvents for projection by an ink jet, and risk sedimenting over time. The desired volume swelling ratio is generally comprised between 1.2 and 10, preferably between 1.5 and 5, and still more preferably between 2 and 4.

This swelling ratio is also valid both for particles with a « core » structure and for particles with a « core/shell » structure.

From known applications of such cross-linked polymers, prepared by aqueous emulsion polymerization, and then precipitated, and put back into solution in an organic solvent, it did not obviously ensue that they may be used as binders of inks capable of being projected by a jet.

Nothing could additionally suggest that, considering the prior art documents, the use of such entirely cross-linked polymers in ink compositions for ink jet printing may provide the markings obtained from these ink compositions, with properties of resistance to abrasion, of flexibility and of adherence notably on flexible substrates such as films, plastic sheets or rubbery substrates.

Thus :

Document US-A-6, 075, 105 describes a radical polymerization method for preparing particles of polymers intended to be used as a toner.

This document does neither describe nor suggest the use of these dispersed and swollen particles in an adequate organic solvent, or their use in inks for ink jet printing.

Document US-B2-7, 449, 501 describes ink compositions for ink jet printing comprising an aqueous medium and microgel particles comprising a cross-linked polymer. In this document, the microgel particles are dispersed in water. No reference is made to a use of such particles in a solvent medium.

Document US-B2-6, 858, 301 describes « core/shell » particles, which are added to inks for ink jet printing in order to improve their durability. These inks are only based on water. Inks based on organic solvents are neither described nor suggested. Further, the core of these particles is not necessarily cross-linked. A dispersion in a solvent of such particles, the core of which is not crosslinked, would have the consequence of releasing non-crosslinked and free linear macromolecules having a very high molecular mass. Such molecules would increase the viscosity of the solutions well beyond what is acceptable for projection by a jet.

Document US-B2-7 , 074 , 842 describes ink compositions comprising particles but these particles are not cross-linked, since their cross-linking is achieved after their being deposited on the supports. There again, the formulations are based on water and not based on organic solvents.

Document US-A-4, 289, 678 describes a polymer prepared by emulsion polymerization, used as a thickener for a fatty ink, but it is specified that this polymer is not cross-linked, and that it is dissolved in non-polar solvents.

Document US-B2-7 , 344 , 752 describes the manufacturing of microgels of the « core/shell » type and their uses as fillers in rubbers. The use of these microgels in organic solvents or in inks for ink jet printing is neither suggested nor mentioned. These patents and the other prior art documents do not include any working example, disclosing microgels in a solvent medium. In particular, these patents neither mention nor suggest the use of such microgels in the binder of ink compositions for ink jet printing, regardless of the type of ink jet printing, i.e. especially « DOD », or « CIJ ».

There is no indication in these documents, which would have suggested that advantageously unexpected properties might be obtained by dispersing such microgels in organic solvents, liquid at room temperature, for formulating inks for ink-jet printing.

Unlike the compositions of the prior art, the ink composition according to the invention contains as a binding resin, entirely cross-linked polymer particles and synthesized by emulsion polymerization in water, generally followed by precipitation of the emulsion, by drying and by dispersion/swelling of the particles in the organic solvent of the ink composition.

Emulsion polymerization is carried out according to one of the numerous thereby designated methods.

The precipitation of the polymer is generally achieved by destabilization of the emulsifier, either in an acid medium for example in a sulfuric acid medium, or in the presence of salts. The salts of multivalent cations such as calcium, aluminium, are the most effective.

The thereby cross-linked polymers may either be rigid or not, depending on whether their glass transition temperature (Tg) is high, above room temperature or low, below room temperature. Their Tg may be comprised between -100°C and +200°C.

In the case when the particles are particles with a core/shell structure, as this has been specified above, the polymer constituting the core may be identical with the polymer which forms the shell, or it may be a different polymer by its monomer composition (i.e. the monomer (s) from which it was prepared), but these respectively core and shell polymers are both 100% cross-linked.

The monomers which may be used for making these polymers are generally selected from monomers with a single unsaturated carbon-carbon double bond of the ethylenic type, such as vinyl monomers and (meth) acrylic monomers.

Examples of these monomers are styrene, vinyltoluene, para-methylstyrene, para-tertiobutyl- styrene, para-hydroxystyrene, butadiene, isoprene, ethylene, vinyl alkylates such as vinyl acetate, vinyl propionate, acrylonitrile, C₁-C30 alkyl acrylates and methacrylates , such as methyl, ethyl, propyl, butyl, isobutyl, 2-ethyl-hexyl, octyl, isooctyl, isodecyl, lauryl acrylates and methacrylates, or further 2 (2- ethoxyethoxy) ethyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, 3 , 3 , 5-trimethylcyclohexyl methacrylate, alkoxylated lauryl acrylates, alkoxylated phenol acrylates, alkoxylated tetrahydrofurfuryl acrylates, C₁2-C14 alkyl methacrylates, caprolactone acrylate, trimethylolpropane triacrylate, dicyclopentadienyl methacrylate, diethylene glycol methyl ether methacrylate, ethoxylated nonyl phenol methacrylate, ethoxylated nonyl phenol acrylate, methoxy polyethylene glycol monoacrylate, methoxy polyethylene glycol monomethacrylate , octyldecyl acrylate, stearyl acrylate, stearyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, tridecyl acrylate, tridecyl methacrylate, triethylene glycol ethyl ether methacrylate, vinyl ethers, glycidyl acrylate and methacrylate.

These monomers may be used alone for forming homopolymers or in combination for forming random or block copolymers for example terpolymers, either linear or branched, etc.

The cross-linking agent is generally selected from monomers comprising several (for example 2, 3 or more) unsaturated carbon-carbon double bonds of the ethylenic type such as di-vinyl monomers and poly (meth) acrylic monomers, for example di (meth) acrylic monomers such as divinylbenzene or trimethylolpropane triacrylate.

The ink composition according to the invention is a non-aqueous composition, which generally means that the ink composition according to the invention, comprises a very small proportion of water.

Thus, the ink composition according to the invention generally comprises less than 0.5% by weight of water, preferably less than 0.1% by weight of water, still preferably less than 0.05% by weight of water based on the total weight of the ink; even better the carrier, vehicle, for example the solvent, and the ink composition may be considered as being essentially free of water (0% by weight of water) . As the provided water is found as an impurity in the various components of the ink, the higher the degree of purity of the selected components, the lower will be the water content. In fact, it may be stated that the ink according to the invention does not contain any added water but only the water provided as an impurity by the different constituents of the ink.

In the same way, the solvent of the ink composition according to the invention is generally non-aqueous in the sense given above, in other words this solvent is essentially, substantially, or exclusively organic.

This absence or quasi-absence of water is also the one of the characteristics which differentiates the ink composition according to the invention from the compositions of the prior art in which the cross-linked particles generally remain in the aqueous medium in which they were prepared and are not dispersed in an essentially, substantially, or exclusively organic solvent like in the ink composition according to the invention .

The binder of the ink composition according to the invention which consists preferably of a binding resin which is obtained by emulsion polymerization, generally accounts for 0.1 to 30% by weight, preferably for 1 to 25% by weight, still preferably for 3 to 20% by weight of the total weight of the ink composition.

In addition to the binding resin consisting of the particles of at least one entirely cross-linked polymer obtained by emulsion polymerization, the binder of the ink composition according to the invention may further comprise one or more other binding resin (s) generally selected from resins soluble in the solvent of the ink composition such as the resins which are soluble in ketone solvents, such as polyacrylates , polymethacrylates , polystyrenes and their copolymers, epoxy, epoxyphenolic resins, melamines, and rosin derivatives .

The carrier, vehicle, generally accounts for 30 to 90% by weight, preferably for 60 to 80% by weight, of the total weight of the ink composition according to the invention.

As this has already been specified above, the carrier comprises, preferably consists of, one or more organic solvents liquid at room temperature.

The solvent (s) of the ink composition according to the invention may be any solvent capable of dissolving the non-cross-linked polymers of the same monomer composition as the cross-linked polymers prepared by polymerization in an aqueous emulsion of the binder of the ink composition according to the invention.

The solvent (s) of the ink composition according to the invention may be selected from ketones, preferably, from aliphatic ketones with 3 to 10 carbon atoms, such as acetone, butanone (methyl-ethyl-ketone) , pentanone-2 (methyl-propyl-ketone) , methyl-3 butanone-2 (methyl- isopropylketone) and methyl-4 pentanone-2 (methyl- isobutyl-ketone) , cyclic ketones such as cyclohexanone ; and their mixtures.

The carrier generally comprises a major proportion by weight (50% by weight of the total weight of the solvent or more) of one or more ketone (s), this (these) ketone (s) being preferably selected from acetone, butanone (methyl-ethyl-ketone) , pentanone-2 (methyl- propyl-ketone) , methyl-3 butanone-2 (methyl-isopropyl- ketone) and methyl-4-pentanone-2 (methyl-isobutyl- ketone) ; preferably, the solvent consists of one or more ketone (s) preferably selected from the ketones mentioned above.

A preferred solvent among all consists of (100%) methyl-ethyl-ketone (MEK) .

One or more organic solvent compound (s) other than the ketone (s) such as MEK, may be added in a minor proportion by weight (less than 50% by weight) , preferably from 5 to 25% based on the total weight of the carrier, vehicle, in order to optimize the properties of the inks. These minor solvents may be selected from esters, ethylene glycol or propylene glycol ethers, and acetals.

The ink composition according to the invention also contains dyestuffs (coloring materials) such as dyes (coloring agents) and pigments.

The dye(s) and/or pigment (s) may be selected from all dyes or pigments suitable for the intended use, known to the man skilled in the art, some of these pigments or dyes have already been mentioned above.

The dyes and the pigments will generally be selected from dyes and pigments known under the name of "C.I. Solvent Dyes" and "C.I. Pigments".

As examples, of the most current pigments and dyes, mention may be made of C.I. Solvent Black 29, C.I. Solvent Black 7, C.I. Solvent Black 28, C.I. Solvent Black 35, C.I. Solvent Blue 70, C.I. Solvent Red 124, dispersions of Pigment Blue 60 or Pigment Blue 15.

Preferred dyes are C.I. Solvent Black 27 and C.I. Solvent Black 29.

The total amount of dye(s) and/or of pigment (s) is generally in the aggregate from 0.05 to 25% by weight, preferably from 1 to 20%, still preferably from 3 to 10% of the total weight of the ink composition.

A dye for which solubility in water is the lowest, which is insoluble in water, will preferably be selected .

By dye insoluble in water, is generally meant a dye which, added at 1% by weight in demineralized water, does not cause coloration of the water, visibly to the eye.

The ink composition may further comprise one or more plasticizer (s) (of the resin (s) or polymer (s) of the binder) for example selected from plasticizers known to the man skilled in the art and selected depending on the binder used comprising one or more polymer (s) and/or resin (s), mention may be made as a plasticizer, for example, of thermoplastic polyurethanes , phthalates, adipates, citrates or further alkyl phosphates.

The plasticizer (s) is (are) generally present in an amount of at least 0.05%, preferably from 0.1 to 20% by weight, of the total weight of the ink composition.

The composition according to the invention if it has to be projectable by a deflected continuous jet, may further optionally comprise at least one conductivity salt, except if another ingredient of the ink such as a dye, is itself a ionizable compound such as a salt which may provide conductivity when it is dissociated, and gives sufficient conductivity to the ink so that there is no need to add any conductivity salt, strictly speaking, this is especially the case of the already mentioned compounds, known under the name « C.I. Solvent Black 27, 29, 35 and 45 ».

Indeed, the ink according to the invention when it has to be applied by a deflected continuous jet, should have sufficient electric conductivity, generally greater than or equal to 5 pS/cm at 20°C, preferably greater than or equal to 300 pS/cm at 20°C, more preferably greater than or equal to 500 pS/cm at 20°C, still preferably of the order of 500 to 2,000 pS/cm at 20°C.

However, it will sometimes be necessary to include, in the ink composition, at least one conductivity salt strictly speaking, different from ionizable compounds, such as the dyes mentioned above, and which is generally selected from salts insoluble in water .

This conductivity salt may thus be selected from salts of alkaline metals such as lithium, sodium, and potassium, salts of earth alkaline metals such as magnesium and calcium, and simple or quaternary ammonium salts; these salts being in the form of halides (chlorides, bromides, iodides, fluorides), perchlorates , nitrates, thiocyanates , formates, acetates, sulfates, propionates, trifluoroacetates , triflates ( trifluoromethane sulfonates) , hexafluoro- phosphates, hexafluoroantimonates , tetrafluoroborates, picrates, carboxylates and sulfonates, etc.

This (these) conductivity salt(s) will therefore be present if necessary, in the ink composition so as to impart to the ink the above conductivity: preferably, their amount is from 0.1 to 20% by weight, still preferably from 0.1 to 10% by weight and better from 0.1 to 5% by weight, of the total weight of the ink composition .

The composition according to the invention may further comprise one or more additives selected from compounds which improve the solubility of some of its components, the printing quality, the adherence, or further the control of wetting of the ink on different supports.

The additive (s) may be selected, for example, from antifoaming agents, chemical stabilizers, UV stabilizers; surfactants, such as Fluorad FC430, agents inhibiting corrosion by salts, bactericides, fungicides and biocides, pH regulating buffers, etc.

The additive (s) is (are) used at very low doses, generally less than or equal to 5% and sometimes as low as 0.01%, depending on whether these are anti-foam agents, stabilizers or surfactants.

The object of the invention is also a method for marking substrates, supports or objects, for example either porous or non-porous, by projection on these substrates, supports or objects with a printing technique by a jet of liquid, of an ink, of an ink composition, as described above. The marking is either carried out by the technique of the deflected continuous jet, or by the "drop on demand" technique.

The object of the invention is further a substrate, support or object, for example either porous or non-porous, provided with a marking obtained by drying and/or absorption (in the substrate or support) of the ink composition, as described above.

Said marking essentially comprises the dye or pigment of the ink as well as the binder, and it is obtained by evaporation and/or absorption in the substrate, of essentially, substantially, the totality of the other constituents of the ink such as the solvents .

This substrate may be made of metal, for example of aluminium, of steel (beverage cans) , of glass (glass bottles) , of ceramic, of a material containing cellulose such as cellophane, paper, optionally coated or glazed, cardboard or wood, of a synthetic (« plastic ») polymer, especially as films, such as PVCs, polyesters, PETs, polyolefins, such as polyethylenes (PE) polypropylenes (PP) , of

« Plexiglas », of fabric, of natural or synthetic rubber, or of any other non-porous or porous substance or of a composite of several of the previous materials.

The substrate is especially a flexible or highly flexible substrate, such as a plastic film, preferably a thin film, in cellophane, polyethylene or polypropylene, especially made of bi-oriented polypropylene; or a rubber substrate. Markings, prints of excellent quality are obtained on all substrates, and in particular on flexible or even highly flexible substrates. These markings, prints, are highly resistant to friction, rubbing, and to creasing even on these flexible or even highly flexible supports.

The invention will be better understood upon reading the following description of embodiments of the invention, given as illustrative and non-limiting examples.

Compositions of inks according to the invention, were prepared by mixing the resins synthesized in Examples 1-3 and 5 or the resin of Example 4 which is the resin Paraloid EXL 2650A, with the other ingredients mentioned in Table II.

Examples 1 to 3 :

In these examples, resins, polymers are synthesized by an emulsion polymerization method.

The operating procedure for synthesizing each of these resins, polymers, is the following:

In a 500 mL flask equipped with a magnetic stirrer, demineralized water is introduced and then a disproportionated rosin potassium soap, the different monomers intended to form the polymer of the relevant example which are mentioned in Table 1 including the monomer playing the role of a cross-linking agent (divinylbenzene) and the radical initiator which is potassium persulfate. The amounts by mass of each of these constituents of the thereby prepared reaction mixture are given in Table 1. After nitrogen bubbling for extracting the dissolved oxygen, the whole is placed in a bath at 60°C with stirring. Periodic samplings allow the progress of the reaction to be tracked by measuring the dry extract. When polymerization is completed, the polymer is recovered by pouring the obtained aqueous polymer emulsion in a solution of 0.1% sulfuric acid in water, whereby the polymer precipitates. The thereby precipitated polymer is recovered by filtration and then dried in an oven.

Example 4 :

In this example, particles with a core/skin or core/shell structure are prepared.

The polymer forming the core of the particles is prepared according to the same operating procedure as the one described above for polymers in Examples 1-3. The monomers which are intended to form the core polymer of the particles as well as the mass proportions of these monomers, are mentioned in Table 1 (column entitled « Example No. 5, Core ») . When 80% of the monomers are polymerized, the monomers intended to form the skin or shell polymer, mixed beforehand, are introduced into the flask and subjected to nitrogen bubbling.

When 100% of the monomers are polymerized, the core/skin particles are recovered as in Examples 1-3.

The compositions of the reaction mixtures used in each of the Examples 1-3, and 5 of the synthesis of polymers by emulsion polymerization are given in the following Table 1. Table 1 also gives the size of the particles of the aqueous polymer emulsion obtained at the end of the emulsion polymerization in said reaction mixture.

Table 1 further indicates the size of the dispersion particles obtained by re-dispersion in methyl-ethyl-ketone of the precipitated polymer particles recovered by filtration at the end of the Examples 1-3, and 5.

In this Table 1, the composition of the Paraloid EXL 2650A which is a polymer prepared by emulsion polymerization and commercially available is also given in Example 4 (comparative example) .

Table 1

at 40% in demineralized water

* 0.75 in 3 times 0.25 after 30 and 60% conversion ** Final particle size = core + shell

Swelling rate of core + shell particles

The polymers prepared in Examples 1 and 2 are polymers with a high Tg, the polymer prepared in Example 3 is a polymer of low Tg (calculated to be -13°C) . The calculated volume swelling rates are comprised between 2 and 10.

In Example 4 (comparative example) , Paraloid EXL 2650A, a polymer polymerized in an emulsion, marketed by Dow Chemical is used. This is a polymer of the « core/shell » type, the « core » of which consists of a butadiene-styrene-polymer with very low Tg and the « shell » or « skin » of which consists of a polymethyl methacrylate polymer, therefore with high Tg. The size of the particles of this polymer in the latex state being unknown, a swelling rate cannot be calculated.

As this was seen above, Example 5 is also a polymer of the « core-shell » type. The swelling rate of the core + shell assembly is 2.05.

The sizes of particles were measured by quasi-elastic scattering of light with a granulometer « Nano-S » from Malvern . The indicated values of particle sizes are the averages of the peaks of the « intensity » distribution calculated by the software of this apparatus according to multimodal analysis.

Ink compositions according to the invention have been prepared by mixing the resins synthesized in Examples 1-3 and 5 or the resin of Example 4 (comparative example) with the other ingredients mentioned in Table 2 hereafter. Table 2

INK COMPOSITION

Constituents (mass No.1 No.2 No.3 No.4 No.5 percentages )

Methylethy1ketone 84,4 81, 9 80,0 79, 9 80

Resin Example 1 10,5

Resin Example 2 8,74

Resin Example 3 16

Paraloid® EXL2650 A 7,5

Resin Example 5 16

Acrylic resin (Neocryl 7,5

B814)

Acrylic resin (Neocryl 2, 91

B813)

Solvent Black 29 5 5 4 5 4 (Orasol® black RLI

Surfactant Byk 333 0,1

Viscosity (mPa.s) 4,7 4,8 4,0 4,1 3, 8

Conductivity (yS/cm) 1100 1050 890 1010 879 The resin Neocryl B814 is a copolymer of methyl and ethyl methacrylates and ethyl acrylate made by DSM- Neoresin. Its Tg is 52°C.

The resin Neocryl B813 is a copolymer of ethyl methacrylate and of an acid monomer giving an acid number of 10 mg KOH/g, made by DSM-Neoresin . Its Tg is 64°C.

The ink compositions according to Table 2, according to the invention, are prepared by mixing the different resins, dyes and other additives in the solvent until complete dissolution.

The formulation, the ink composition No. 1 according to the invention was tested in Markem-Imaje printers of the continuous jet type and it was possible to obtain excellent quality prints.

Further, the markings thereby made with the ink composition No. 1 on aluminium or PVC films are more resistant to rubbing than markings made with a formulation, a comparative ink composition, non-compliant with the invention, which is a formulation, with a composition similar to the inventive composition, ink formulation No. 1, but which does not comprise the resin synthesized in Example 1.

The rubbing test consisted of carrying out 10 rubbings by strongly pressing a finger on a square of Joseph paper on ink jet markings respectively made with the ink composition No. 1 according to the invention or with the comparative ink composition not comprising the resin of Example 1.

The formulation, the ink composition No. 2 according to the invention was tested in Markem-Imaje printers of the continuous jet type and prints of excellent quality were able to be obtained.

Further, the thereby produced markings with the formulation, the ink composition No. 2 according to the invention on highly flexible plastic films made of bi-oriented polypropylene or of polyester are more resistant to creasing, during a hand creasing test than markings produced with a comparative formulation, non-compliant with the invention, which is a formulation similar to the composition No. 2 according to the invention, but which does not comprise the resin synthesized in Example 2 (all the other components being identical) .

The formulation No. 4 (comparative) did not give

® good quality printing by projection in a Markem-Imaje printer of the deflected continuous jet type. However, it was deposited with the fluted bar applicator on bi-oriented polypropylene and polyester films, the deposits are extremely more resistant to creasing than a similar formulation but with the sole Neocryl ® resin.

®

GPC analysis of the Paraloid EXL 2650A resin showed the presence of cross-linked molecules with high molecular masses.

This resin therefore does not seem to consist of only entirely cross-linked particles like the particles of the composition according to the invention. Whence the poor printing quality obtained.

The formulation No. 5 according to the invention was tested in Markem-Imaje printers of the continuous jet type and prints of excellent quality were able to be obtained.

Claims

1. A non-aqueous ink composition for liquid jet printing comprising:

- a carrier, vehicle, comprising, preferably consisting of, one or more organic solvent (s) liquid at room temperature;

- one or more dye(s) and/or pigment (s);

- a binder, comprising at least one binding resin consisting of particles of at least one entirely cross-linked polymer, having a cross-linking level of 100%, obtained by polymerization in an aqueous emulsion of at least one monomer selected from monomers with a single unsaturated carbon-carbon double bond of the ethylenic type, and of at least one cross-linking agent .

2. The ink composition according to claim 1, wherein the binder comprises at least 10% by weight, preferably at least 50% by weight of said at least one binding resin.

3. The ink composition according to claim 2, wherein the binder consists of said at least one binding resin.

4. The ink composition according to any one of the preceding claims, wherein the particles are particles with a « core » structure, each particle with a « core » structure consisting of a single, entirely cross-linked, polymer, with a cross-linking level of 100%, each particle only consisting of one single polymer molecule.

5. The ink composition according to any one of claims 1 to 3, wherein the particles are particles with a « core/shell » structure, the core and the shell consisting respectively of a first polymer and a second polymer, different from each other, each of said polymers being entirely cross-linked.

6. The ink composition according to claim 5, wherein the core of the particles consists of one single molecule of the first polymer and the shell of the particle consists of one single molecule of the second polymer, or else the core and the shell only consist together of one single and same molecule.

7. The ink composition according to claim 5 or 6, wherein the core of the particles consists of a first polymer with a glass transition temperature of less than 0°C, and the shell of the nanoparticles consists of a second polymer with a glass transition temperature of greater than 20°C.

8. The ink composition according to any one of the preceding claims, wherein the particles have a spherical or spheroidal shape.

9. The ink composition according to any one of the preceding claims, wherein the particles with a « core » structure have a size defined by their largest dimension, for example their diameter, of less than or equal to 1 ym, preferably from 25 nm to 1 ym, and the particles with a « core/shell » structure have a core of a size of less than or equal to 1 ym, preferably from 25 nm to 1 ym, and a shell of a thickness from 0 to 80 nm.

10. The ink composition according to any one of the preceding claims, wherein the molecular mass of each particle is from 4.10^s to 2.10⁹ daltons, preferably from 4.10⁷ to 4.10⁸ daltons.

11. The ink composition according to any one of the preceding claims, wherein the particles have a polydispersity index, measured by quasi-elastic light scattering, of less than 0.5, preferably less than 0.2.

12. The ink composition according to any one of the preceding claims, wherein the particles have a volume swelling ratio from 1.2 to 10, preferably from 1.5 to 5, and still preferably from 2 to 4.

13. The ink composition according to any one of the preceding claims, wherein said monomer with a single unsaturated carbon-carbon double bond of the ethylenic type is selected from vinyl monomers and (meth) acrylic monomers such as styrene, vinyltoluene, para-methylstyrene, para-tertiobutylstyrene, para- hydroxy-styrene, butadiene, isoprene, ethylene, vinyl alkylates such as vinyl acetate, vinyl propionate, acrylonitrile, C1-C30 alkyl acrylates and methacrylates , such as methyl, ethyl, propyl, butyl, isobutyl, 2- ethyl-hexyl, octyl, isooctyl, isodecyl, lauryl acrylates and methacrylates or further 2 (2- ethoxyethoxy) ethyl acrylate, 2-phenoxyethyl acrylate, 2-phenoxyethyl methacrylate, 3 , 3 , 5-trimethylcyclohexyl methacrylate, alkoxylated lauryl acrylates, alkoxylated phenol acrylates, alkoxylated tetrahydrofurfuryl acrylates, C12-C14 alkyl methacrylates, caprolactone acrylate, dicyclopentadienyl methacrylate, diethylene glycol methyl ether methacrylate, ethoxylated nonyl phenol methacrylate, ethoxylated nonyl phenol acrylate, methoxy polyethylene glycol monoacrylate, methoxy polyethylene glycol monomethacrylate , octyldecyl acrylate, stearyl acrylate, stearyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, tridecyl acrylate, tridecyl methacrylate, triethylene glycol ethyl ether methacrylate, vinyl ethers, glycidyl acrylate and methacrylate.

14. The ink composition according to any one of the preceding claims, wherein the cross-linking agent is selected from monomers comprising several unsaturated carbon-carbon double bonds of the ethylenic type such as di-vinyl monomers and poly (meth) acrylic monomers, for example di (meth) acrylic monomers such as divinylbenzene or trimethylolpropane triacrylate.

15. The ink composition according to any one of the preceding claims, wherein the binder accounts for 0.1 to 30% by weight, preferably for 1 to 25% by weight, still preferably for 3 to 20% by weight of the total weight of the ink composition.

16. The ink composition according to any one of the preceding claims, wherein in addition to the binding resin consisting of the particles of at least one entirely cross-linked polymer, the binder further comprises one or more other binding resin (s) .

17. The ink composition according to any one of the preceding claims, wherein the carrier, vehicle, accounts for 30 to 90% by weight, preferably for 60 to 80% by weight, of the total weight of the ink composition .

18. The ink composition according to any one of the preceding claims, wherein the solvent (s) of the composition is (are) selected from ketones, preferably, from aliphatic ketones with 3 to 10 carbon atoms, such as acetone, butanone (methyl-ethyl-ketone) , pentanone-2 (methyl-propyl-ketone) , methyl-3 butanone-2 (methyl- isopropylketone) and methyl-4 pentanone-2 (methyl- isobutyl-ketone) , cyclic ketones such as cyclohexanone ; and mixtures thereof.

19. The ink composition according to claim 18 wherein the carrier comprises a major proportion by weight of one or more ketone (s), and preferably the solvent consists of one or more ketone (s) .

20. The ink composition according to claim 19 wherein the carrier consists of methyl-ethyl-ketone (MEK) .

21. The ink composition according to claim 19 wherein one or more organic solvents other than ketone (s) such as MEK, are added in a minor proportion by weight, preferably from 5 to 25% based on the total weight of the carrier, vehicle.

22. The ink composition according to any one of the preceding claims, wherein said dye(s) and/or pigment (s) is (are) selected from dyes and pigments known under the name of "C.I. Solvent Dyes" and "C.I. Pigments", such as C.I. Solvent Black 29, C.I. Solvent Black 7, C.I. Solvent Black 28, C.I. Solvent Black 35, C.I. Solvent Blue 70, C.I. Solvent Red 124, dispersions of Pigment Blue 60 or Pigment Blue 15.

23. The ink composition according to any one of the preceding claims, comprising in the aggregate from 0.05 to 25% by weight of dye(s) and/or pigment (s), preferably from 1 to 20%, still preferably from 3 to 10% by weight of dye(s) and/or pigment (s) based on the total weight of the ink composition.

24. The ink composition according to any one of the preceding claims, further comprising one or more plasticizer (s) in an amount of at least 0.05%, preferably from 0.1 to 20% by weight, of the total weight of the ink composition.

25. The ink composition according to any one of the preceding claims, further comprising at least one conductivity salt in an amount from 0.1 to 20% by weight, preferably from 0.1 to 10% by weight and still preferably from 0.1 to 5% by weight, of the total weight of the ink composition.

26. The ink composition according to claim 25 wherein said conductivity salt is selected from salts insoluble in water, such as salts of alkaline metals such as lithium, sodium, and potassium, salts of earth alkaline metals such as magnesium and calcium, and simple or quaternary ammonium salts; these salts being in the form of halides, perchlorates , nitrates, thiocyanates , formates, acetates, sulfates, propionates, trifluoroacetates , triflates

( trifluoromethane sulfonates) , hexafluorophosphates , hexafluoroantimonates , tetrafluoroborates , picrates, carboxylates and sulfonates.

27. The ink composition according to any one of the preceding claims, which has a conductivity in the liquid state, greater than or equal to 5 pS/cm at 20°C, preferably greater than or equal to 300 pS/cm at 20°C, still preferably greater than or equal to 500 pS/cm at 20°C, better from 500 to 2,000 pS/cm at 20°C.

28. The ink composition according to any one of the preceding claims, further comprising one or more additives selected from antifoaming agents; chemical stabilizers; UV stabilizers; surfactants; agents inhibiting corrosion by salts; bactericides; fungicides and biocides; and pH regulating buffers.

29. A method for marking substrates, supports, or objects by projection on these substates, supports or objects, of an ink by a liquid jet printing technique, characterized in that the projected ink is an ink composition according to any one of claims 1 to 28.

30. A substrate, support, or object, characterized in that it is provided with a marking obtained by drying and/or absorption of the ink composition according to any one of claims 1 to 28.

31. The substrate, support, or object according to claim 30, characterized in that the substrate is made of metal, for example of aluminium, of steel; of glass; of ceramic, of a material containing cellulose such as cellophane, paper, optionally coated or glazed paper, cardboard or wood; of a synthetic polymer (« plastic ») especially as films, such as PVCs, polyesters, PETs, polyolefins, such as polyethylenes (PEs) , polypropylenes (PPs) ; of « Plexiglas »; of fabric, of natural or synthetic rubber, or of any other non-porous or porous substance or of a composite of several of the previous materials.

32. The substrate according to claim 31, which is a flexible substrate.