ENERGY CURABLE GRAVURE AND INK JET INKS INCORPORATING GRAFTED PIGMENTS

Abstract: Solvent-free, energy curable low viscosity gravure and ink jet inks which contain a pigment; a rheological additive having the structure P-(U-Y)s, wherein P is the residue of an organic pigment or dye, Y is a polyalkylene oxide moiety, U is a linking moiety covalently bonding Y to P and s is an integer from 1 to 3; and an energy curable liquid vehicle which may be an ultraviolet cationic, thermal cationic or a free radical initiated polymerization system, cured by actinic radiation; and optionally containing a photoinitiating system.

Description: ENERGY CURA3LE GRAVURE AND INK JET INKS INCORPORATING GRAFTED PIGMENTS RELATION TO OTHER PATENT APPLICATIONS This application is a continuation-in-part of U.S. patent application Ser. No. 08/878,590 filed June 19, 1997. BACKGROUND OF THE INVENTION Field of the Invention This invention relates to low viscosity energy curable gravure and ink jet printing inks and methods for using same. Description of Related Art Low viscosity and good flow are the most important factors affecting liquid ink behavior and improved printability. These factors are particularly important for formulating inks for ink jet and gravure printing applications . Schwartz et al . in U.S. Patent 4,468,255, disclose rheology modifiers for arylide yellow pigment dispersions. The rheology modifiers which are derived from diarylide pigments improve the fluidity of non- aqueous arylide pigment dispersions prepared from either rnonoarylide or diarylide yellow pigments. Schwartz et al . in a series of patents (i.e., U.S. Patents 4,946,508; 4,946,509; 5,024698; and 5,062,894) have disclosed modified azo pigments for use in conventional, solvent and water based inks and coatings to function as rheology control agents. In each of these patents, Schwartz et al . modify an azo pigment (e.g., a diarylide pigment, a monoazo pigment, a άisazc pyrazolone pigment and the like) by grafting a pclyal yl e oxide tc the pigment sc that water based inks made from these pigment compositions exhibit high colcring strength, cleaner shades, lower rheology, and enhanced gloss compared with conventional water based inks. To increase printing throughput, ultraviolet (UV) or electron beam (EB) curable inks have been developed that allow printers to reduce the solvent content of the ink. It is always a challenging task for a UV cr EE curable liquid ink formulator to develop ink formulations with a viscosity low enough for improved flow, while at the same time maintaining other essential characteristics, such as to cure, adhesion, low odor, etc. Traditional organic and inorganic pigments used in formulating energy curable liquid inks, are poorly dispersed in the vehicles used in the systems. As a result, poor pigment wetting leads to a thixotropic structure. If the inks are not subjected to high shear, the apparent viscosity will remain high and the ink will exhibit poor transfer resulting in poor printability. Flow additives have been tried, however, with limited success for different pigments. The situation becomes more critical in the case of cationic curable inks, where not all the pigments and additives can be used due to the presence of basic functionalities. In addition, some energy curable inks of the prior art contain fugitive solvent (such as water, alcohols and the like) as part of the vehicle to reduce viscosity, aid in pigment dispersion, and modify flow during printing. However, after printing but before curing, the fugitive solvent is typically removed to prevent interference with the curing process and to prevent it from having an adverse affect on the printed image. The curing delay required by solvent removal, as well as attendant unpleasant odors, are further undesirable limitations to printing. Furthermore, solvent removal is desirable for environmental reasons. A UV- cured ca or.icallv oclvτrierizεd rir.tmα ink is disclosed by Seng in Patent Application DE 195 00 968.1 for use in indirect letterpress printing cr dry offset printing. Seng lists the differences between letterpress and flexographic printing and the list includes critical differences in ink viscosities. In particular, Seng discloses that printing inks used in flexographic printing have viscosities in the range of 0.01 to 2 cos and at 20°C in the range of 3.0 to 100.0 cpε , and more preferably in the range of 4.0 to 10 cps . Seng's inks are cationically polymerized and differ from the very high viscosity printing inks used in indirect letterpress printing in solvent content. While inks of this viscosity range are useful in high shear, indirect letterpress printing, such inks have high tack which causes them to be unsuitable for low shear applications such as flexography, which requires low tack inks. Although improvements have been made in energy curable cationic ink formulations, there continues to be a need for energy curable ink formulations (including free radical initiated curable formulations) which have a high color strength, cleaner shade and enhanced gloss but retain a very low viscosity as required by flexographic and ink jet printing. SUMMARY OF THE INVENTION In one aspect, the invention is an energy curable gravure ink comprising a pigment, a rheological additive having the structure : P- (U-Y) s wherein ? is the residue cf an organic colorant, Y is a polyalkylene cxide moiety, U is a linking moiety covalently bending Y to ? and s is an integer from 1 :: 3; and an energy curable liquid vehicle; wherein the ink is substantially free of fugitive solvent and has a viscosity ranging from about 8 cps to about 200 cps . In another embodiment of this invention, this energy curable gravure ink further comprises a polymerization initiating system activatable by actinic radiation. Another embodiment cf this invention involves a method cf gravure printing and curing the gravure ink composition comprising the steps of: preparing the energy curable gravure ink described supra; printing the ink onto a substrate surface to form an ink image; and subjecting the ink image to actinic radiation or thermal energy to form a cured ink image. Another aspect of this invention involves an energy curable ink jet ink comprising a pigment, a rheological additive having the structure: P- (U-Y) wherein P is the residue of an organic colorant, Y is a polyalkylene oxide moiety, U is a linking moiety covalently bonding Y to P and s is an integer from 1 to 3; and an energy curable liquid vehicle; wherein the ink is substantially free of fugitive solvent and has a viscosity ranging from about 8 cps to about 200 cps. In another embodiment of this invention, this energy curable ink jet ink further comprises a polymerization initiating system activatable by actinic radiation. A further embodiment cf this invention involves a method cf ink jet printing and curing an ink jet ink composition comprising the steps of: preparing the energy curable ink jet ink described supra; printing the ink onto a substrate surface to form an ink image; and subjecting the ink image to actinic radiation cr thermal energy to form a cured ink image . DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a novel solvent-freε , energy curable gravure and ink jet printing inks having low to very low viscosities and their application. The term "energy curable or cured" as used herein, in reference to ink means an ink which can be cured, hardened, polymerized, or crosslinked by the action of actinic radiation such as UV or EB radiation and the like from a radiant energy source; or from a thermal energy source by heating with a conductive or radiant heat source such as a platen, an oven, infrared (IR) , microwave, and the like. The energy curable ink of this invention comprises a pigment composition and an energy curable liquid vehicle is substantially free of a fugitive solvent. The terms "substantially free of fugitive solvent" and " solvent - free", as used herein in reference to inks, means free of a liquid component (e.g., water, lower alcohols, alkanes, aromatics, aliphatics, ketones, acetates and the like) which, after printing, is evaporated, imbibed into a substrate surface, or both, and does not remain as an essential component of the cured ink. Further, these terms are not intended to exclude trace or residual solvents resulting from the manufacture of ink components prior to ink formulation. The term "colorant", as used herein means an organic pigment or dyestuff. The energy curable liquid vehicle typically comprises one cr more low molecular weight mono- or multi-functional monomers. For offset inks and other inks which require higher viscosities, a resin, a reactive oligomer or polymer may also be present. The inks of the present invention may be cured thermally or by actinic radiation sources, such as electron beams and the like; or photolytically cured by actinic radiation, such as UV radiation and the like, when a suitable initiating system is incorporated into the ink. The solvent-free, energy curable inks of this invention are more fully described in the following examples . Piαment The pigment is any organic pigment that can be employed for the coloration of conventional printing inks of the prior art. The pigment may also be carbon black. Pigments suitable for use in the present invention may be any conventional organic pigment such as: Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigment Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yellow 37, Pigment Yellow 63, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 106, Pigment Yellow 114, Pigment Yellow 121, Pigment Yellow 126, Pigment Yellow 127, Pigment Yellow 136, Pigment Yellow 174, Pigment Yellow 176, Pigment Yellow 188, Pigment Orange 5, Pigment Orange 13, Pigment Orange 16, Pigment Orange 34, Pigment Red 2, Pigment Red 9, Pigment Red 14, Pigment Red 17, Pigment Red 22, Pigment Red 23, Pigment Red 37, Pigment Red 38, Pigment Red 41, Pigment Red 42, Pigment Red 112, Pigment Red 146, Pigment Red 170, Pigment Red 196., Pigment Red 210, Pigment Red 238, Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigment Green 7,. Pigment Green 36, Pigment Violet 23, or carbon black, including Pigment Black 7 and the like. R-ec oα-CcL z .dd_. iλ' , e The rheological additive is a polyal ylene oxide covalently bonded (i.e. grafted) to the residue of an organic colorant and has the structure P-(U-Y) S , m which P is the residue of an organic colorant, Y is a polyalkylene oxide moiety containing aoout 4 to about 400 alkylene oxide repeat units, and U is a linking moiety covalently bonding Y to P and s is an integer from 1 to 3. Typically, P is a residue of a pigment, such as, a residue of an azo pigment, phthalocyanme pigment, dioxazme pigment, qumacridone pigment, perylene pigment, permone pigment or the like. Preferably, P is the residue of a diarylide pigment, monoazo pigment, diεazo pyrazolone pigment, phthalocyanme pigment, or perylene pigment. The polyalkylene oxide moiety, Y, may be the residue of any polyalkylene oxide such as an ethylene oxide polymer, an ethylene oxide/propylene oxide copolymer and the like. Preferably, Y is an alkylene oxide copolymer having the general formula. Q , -0-(CH_CHO)_-CH_CH- I I Q Q wherein n is about 4 to about 400 and more preferably is about 4 to about 60; Q is H, CH 3 or a combination thereof; and Q 1 is a Cj.-C 6 alkyl moiety. The weight average molecular weight of the polyalkylene oxide moiety typically is between about 300 and 3,600; and preferably between about 1,000 and 3,000 The polyalkylene oxide moiety, Y, may be grafted to the residue of an organic colorant, P, through a linking moiety, U, which is preferably a covalent bend or multivalent moiety such as Cι-C« alkyl, -NHSO;-, -0-, - C- , -C00-, -N-, -CONK-, and the like. It is understood that the particular linking moiety employed will be determined by those skilled in the art depending on the nature of P. Combinations of pigment and rheological additive particularly useful in the solvent free energy curable inks of the invention are described in U.S. Patents 4,946,508; 4,946,509; 5,024,698; and 5,062,894; each of which is incorporated herein by reference. In particular, Schwartz et al , U.S. Patent 4,946,508 discloses disazo pvrazolone compositions which contain said rheological additives and their method of manufacture. Such disazo pyrazolone pigment compositions have the general formula: Formula I wherein Y is the polyalkylene oxide moiety; R is H, CH 3 , OCH 3 , OCH 2 CH 3 or Cl; n is selected from an integer from 1 to 5; R 2 is CH 3 or COOOCH 2 CH 3 ; R 3 is H or CH 3 ; and XI is Cl of OCH 3 U.S. Patent 4,946,509, Schwartz et al discloses azomethine compositions and their method of manufacture. Such azomethine pigment compositions have the general formula: Formula II wherein Y is the polyalkylene oxide moiety containing about 4 to about 200 groups; R and Rl are independently selected from the group consisting of H, CH 3 , OCH 3 , OCH 2 CH 3 and Cl ; n is selected from an integer from 1 to 5 ; X is selected from the group consisting of Cl, CH 3 , OCH 3 ; and Z is selected from 0 and N-Y. U.S. Patent 5,024,698, Schwartz et al discloses monoazomethine compositions and their method of manufacture. Such monoazomethine pigments have the general formula: Formula HI wherein Y is the polyalkylene oxide moiety; R 6 is independently selected from the group consisting of Cl , OCH 3 , CH 3 , 0C 2 H_, C 2 H 5 , and C0NH 2 ; R 7 is independently selected from the group consisting of Cl , 0CH 3 , CH 3 , N0 2 , OC 2 H 5 , C 2 H 5 , CONK 2 , SC 3 H, OH and COOK; and a ana b are independently selected from integers 0 to 5. U.S. Patent 5,062,894, Schwartz et al discloses diarylide compositions and their method of manufacture. Such diarylide pigment compositions have the general formula: FormulaIV wherein R 4 and R s are independently selected from the group consisting Of C_-C 4 alkyl, C_-C 4 alkoxy, and halogen; m and p are independently selected from integers of 0 to 5; X 2 is selected from the group consisting of Cl, CH 3 , and OCH 3 ; U 2 comprises a divalent bridging moiety selected from the group consisting of C_-C 6 alkyl , -NKS0 2 - , -0-, -CO-, -COO-, and -CONH-; Y 1 comprises the polyalkylene oxide moiety having a number average molecular weight of about 200 to 10, 000; and k and 1 are independently selected from integers 0 or 1 , with the proviso that for at least 50 wt . % of the composition, k and 1 are both 0, and for at least 3 wt . % of the composition k and/or 1 are 1. Other rheological additives particularly useful i the energy curable inks cf this invention, include phthalocyanme compositions having the P-U-Y structure in which P, is the residue cf a copper pntr.alccyanine pigment and wherein the linking moiety, U, is -NHS0 2 - which joins P to Y. Such copper phthalocyanme based rheological additives have the general formula: wherein Y is a polyalkylene oxide moiety which has the general formula: Q '- 0 -(CH_CHO)„-CH . CH- I I Q Q wherein n is about 4 to about 400, and a, b, c and d are integers independently from 0 to 4 , provided at least one of them is 1; Q is selected from H, CK 3 or a combination thereof; and Q' is a Cι-C 6 alkyl moiety. The rheological additive used in this invention may be prepared by any conventional method. Illustrative methods for preparing the pigments with the rheological additives described herein are disclosed in U.S. Patents 4,946,508; 4,946,509; 5 , 024 , 698 ; and 5,062,894 and in the Examples . The pigment compositions used in this invention typically contain a miner portion of said rheological additive and a major portion of the conventional pigment. The residue of the organic colorant that is contained in the rheological additive does not need to be of the same type as the pigment of the ink formulation. For example, the additive of Formula V may be utilized with Pigment Violet 23 or Pigment Black 7. An advantage of the preparation methods disclosed in the Schwartz et al . patents supra, is that a blend of the colorant additive and the pigment is produced directly, and may be used without further blending. To produce printing inks with a desired hue, a separate pigment may be added which is distinct from the pigment and rheological additive. Methods of effecting a desired hue from precursor pigments are well known to the ink formulator and are illustrated in the examples. Enerαv Curable Liσuid Vehicle The solvent -free, energy curable ink of this invention contains as the third essential component a quantity of an energy curable liquid vehicle which is substantially free of fugitive solvent. The quantity of liquid vehicle employed is an amount sufficient to make up 100% of the ink weight when taken together with other ink components. The radiation curable liquid vehicle typically comprises one or more low molecular weight mono-functional or multi-functional monomers. For offset inks and other inks which require higher viscosities, a resin, a reactive oligomer or polymer may also be present. These components may react with the monomers upon curing. The energy curable liquid vehicle is characterized in that it is curable to a solid by exposure to energy from a radiant cr thermal energy source as described supra. The liquid vehicle may be cured to a solid by exposure to energy, such as exposure to high energy electrons from an electron beam source. Alternatively, curing of the liquid vehicle may be initiated by energy activation of a polymerization initiating system (e.g. by UV radiation) as will be described in detail hereinbelow. In this context, a polymerization initiating system may be considered an optional component of the energy curable liquid vehicle. The liquid vehicle may be a ring opening polymerizable composition, a free radical addition polymerizable composition, or by a combination of ring opening and free radical polymerization. In either composition, the liquid vehicle is cured or hardened by polymerizing and/or crosslinking, at least the reactive monomers of the liquid vehicle. In order to reduce environmental contamination and maintain formulation integrity, the liquid vehicle is typically formulated with components having low volatility under ambient printing conditions. When the liquid vehicle is a ring opening polymerizable composition, upon energy initiation it forms a polymer typically bound by ester, or ether linkages. In a preferred embodiment of the invention the polymerizable composition is a cationic polymerizable system comprising one or more mono-functional or multi functional epoxides . The liquid vehicles typically contain at least one cycloaliphatic epoxide. Examples of such cycloaliphatic epoxides are adducts of epoxides and hydroxyl components such as glycols, polyols, or vinyl ether, such as 3 , 4-epoxycyclohexylmethyl 3,4-epoxy- cyclohexane carbcxylate; bis (3 , 4-epoxy-cyclohexyl - methyl) adipate; limonene monoepoxide; limonene diepoxidε; ciglycidyl ester of hexahydrophthalic acid; l-vinyl-3,4- epcxycyclohexanε; epcxidated dicyclopentyl alcohol; or a mixture thereof. A preferred cycloaliphatic epoxides of this type is 3 , 4-epoxycyclohexylmethyl 3 , 4-epoxy-cyclo- hexylcarboxylate; 1, 3-bis (2- (7-oxabicycio (4.1.0) hepta-3- yl) ethyl) -1, 1, 3, 3-tetramethyldisiloxane. In addition to the cycloaliphatic epoxides there may be one or more noncycloaliphatic epoxides, such as di- or tri-glycidyl ether, alkoxylatεd bisphenol A, 1,6-hexane diol, glycerol; neopentylglycol ; or trimethylolpropane . The epoxy diluent likewise may be diglycidyl ether of bisphenol A; an alpha-olefin epoxide, a Novalac epoxide, epoxidated linseed oil, soy oil; epoxidated polybutadiene; 1, 2-epoxydecane; caprolactone triol; glycidyl ether; alkyl glycidylether; epoxidated silanes; glycidoxy-methoxy silane; and glycidoxy-ethoxy silane; 2- ethylhexylglycidyl ether. In such epoxy compositions, the ink typically contains a cationic initiating system activatable by actinic radiation as will be described hereinbelow. A preferred epoxy diluent is 2- ethylhexylglycidyl ether. In such epoxy compositions, the ink typically contains a cationic initiating system activatable by actinic radiation as will be described hereinbelow. When the energy curable liquid vehicle is a free radical addition polymerizable composition, the vehicle comprises a liquid compound having terminal ethylenic unsaturation. Typically, the liquid vehicle is a free radical addition polymerizable system comprising an ethylenically unsaturated mono- or multi-functional monomer. The monomer is a lower molecular weight ethylenically unsaturated compound which forms a polymer directly upon initiation by free radicals generated by absorbed energy. In some formulations an oligomeric or polymeric component which can be further polymerized may also be present. In such cases the further polymerizable material will be soluble in, or dispersible in the monomer vehicle. Typically, the mcnomeric compounds have one, two, or more terminal ethylenically unsaturated groups. Representative of such monomeric compounds are: N-vinyl pyrrolidinone; dipropylene glycol diacrylate; tripropylene glycol diacrylate; butanediol diacrylate; hexanediol diacrylate; trimethylol propane triacrylate; ethoxylated trimethylol propane triacrylate; glycerol- propoxy triacrylate; pentaerythritrol triacrylate; dipropylene glycol dimethacrylate; tripropylene glycol dimethacrylate; butanediol dimethacrylate; hexanediol dimethacrylate; trimethylol propane trimethacrylate; di- (3-methacryloxy-2-hydroxypropyl ether) of bisphenol-A; di (2methacryloxyethyl ether) of bisphenol-A; di-(3- acryloxy-2-hydroxypropyl ether) of bisphenol-A; di(2- acryloxyethyl ether) of bisphenol-A; and the like. To achieve the desired ink viscosity and crosslinking properties, typically the monomer composition contains a combination of multifunctional acrylic monomers along with a monomer containing a single terminal ethylenic group, as illustrated in the examples which follow. When the inks of this invention contain an oligomeric or polymeric material, said materials typically possess ethylenic unsaturation which can react with the ethylenically unsaturated monomers. Representative of such oligomers are acrylated epoxy resins; acrylated polyurethanes; acrylated polyesters; and the like. The inks of the present invention may also contain a preformed polymer such as an acrylic polymer or copolymer of Cχ-C alkyl acrylates or methacrylates , or acrylic or methacrylic acid, vinyl polymers and copciymers such as polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol, pclyvinylpyrolidone, celluloεic polymers and ccpclymers; and the like. Polymerization Initiating System Unless the ink is formulated specifically for use with EB curing, it will contain a polymerization initiating system activatable by actinic radiation, such as UV or thermal radiation. Such a photoinitiator system has one or more compounds that directly furnish cations or free radicals when activated by actinic radiation. UV cationic polymerization initiating systems typically are used to initiate ring opening polymerization in systems such as the epoxy compositions described herein. Such cationic initiating systems include all substances which liberate Lewis acids or Brδensted acids upon exposure to actinic radiation. Cationic photoinitiating systems which are particularly useful in the energy curable inks of this invention are arylsulfonium salts, especially the triarylsulfonium salt such as triarylsulfonium phosphate, triarylsulfonium antimonate, triphenylsulfonium hexafluorophosphate, and diarylsulfonium salt; and aryl-iodonium salts, such as diaryliodonium hexafluoroantimonate, bisdodecyldiphenyliodonium hexafluoroantiminoate, and the like. Such cationic photoinitiators may be used individually or in combination to effect suitable curing of the ink. Preferred are diaryliodonium hexafluoroantimonate and (n s -2 , 4-cyclopentadienl- yl) [ (1,2,3,4,5, 6-n) (1-methylethyl) benzene] -iron + - hexafluorophosphate (-1) . In thermal cationic polymerization initiating systems such as the thermal cationic inks described herein, a blocked acid is typically used because it does not initiate the ring opening polymerization of epoxies until it is unblocked. Thermal irradiation unblocks the acid and generates a strong acid, which starts the epoxy ring opening polymerization. Some examples of "blocked" acids are Nacure TLC 1412 (King Industries) , FC-122 and FC-520 (Available from 3M, St. Paul, MN) , and CP-66 (Available from Ciba, White Plains, NY) . Free radical polymerization initiating systems are also possible and typically require irradiation of a photoinitiator to produce free radicals that initiate polymerization. A wide variety of these photoinitiators may be used in the energy curable inks of this invention. A few are described, for example, by B.M. Monroe and G.C. Weed in Photoinitiators for Free-Radical-Initiated Photo- Imaαinα Systems, Chem. Rev. 93, pp. 435-48 (1993), incorporated herein by reference. The reference describes the use of thioxanthone, ethyl 4- (dimethyl- amino) benzoate, alpha amino acetophenone, and Michler's ketone as photoinitiators. Adjuvants The radiation curable inks of this invention may optionally contain the usual adjuvants to adjust ink flow, surface tension, surface penetration and gloss of the cured printed ink. Such adjuvants contained in the ink typically are a surface active agent, a wax, a humectant or a combination thereof. These adjuvants may function as leveling agents, wetting agents, dispersants, defrothers or deareators, or additional adjuvants may be added to provide a specific function. Preferred are isopropyl adjuvants include fluorocarbon surfactants such as FC430, available from the 3M Company; silicones such as DC57, available from the Dow Chemical Corporation; polyethylene wax; polyamide wax; polytεtrafluoroethylene wax; and the like. Printing Ink Formulation The solvent-free, energy curable ink contains as its essential ingredients typically about 2 to about 15 % by weight of pigment, about .1 to about 10 % by weight of rheological additive and the balance being the liquid energy curable vehicle which is substantially free of a fugitive solvent. The energy curable liquid vehiclε typically comprises, one or more low molecular weight mono-functional or multi-functional monomers. Fcr offset inks and other inks which require higher viscosities (>1,000 cps), a resin, a reactive oligomer or polymer may also be present. In addition to the essential ingredients the enεrgy curablε ink may also contain up to about 6 % by weight of polymerization initiating system activatable by actinic radiation; and up to about 10 % or less by weight of a surface active agent, a wax, humectant or combination therεof . Thε primary advantagε offεred by the solvent- freε, energy curable inks of this invention arε that the rhεology may bε readily adjusted to provide an ink viscosity anywhere between about 3 cps to about 200 cps, preferably about 8 cps to about 20 cps (@ 240 s "1 and 25°C) for the energy curable gravure inks described herein. Also, viscosities of about 3 cps to about 25 cps, preferably about 3 cps to about 15 cps (@ 240 s "1 and 25°C) are achievable for the energy curable ink jet inks described herεin, simply by adjusting the ratio of the various types of monomer component, and/or by adjusting the ratio of pigment and rheological additive to liquid vehicle; and/or by adjusting both ratios. The combination of pigment and rheological additive as described herein produces very fine or sub-micron pigment particle sizes that do not clog ink jet nozzles. In addition, these sub-micron particle sizes allow viscoεitiεs εuitablε for ink jεt printing to be achieved. The ink may be preparεd by any conventional mixing and milling method typically uεed for preparing printing inks. Typically, the pigment and rheological additive are mixed with the liquid vehicle thεn milled. After milling additional liquid vehicle and any desirable adjuvants are optionally added and mixed to produce the energy curable ink. As indicated the above mentioned ratios are adjusted to achieve a printing ink with the deεirεd viscosity, flow, color density, and curing characteristics. The ink formulation process is more fully dεscribed in the examples. Mεthod of Printing and Curing This invεntion is also directed to a method of printing and curing an ink image comprising the steps of: preparing solvent-freε enεrgy curable inks as described supra; (b) printing the inks on a substrate surface to form an image; and (c) subjecting the image to actinic radiation or thermal enεrgy to form a cured ink image. Thε method is particularly directed to printing operations requiring low viscosity inks such gravure and ink jet printing. It is understood, however, that any suitable printing and curing means may be used to print and cure the solvent-frεε energy curable ink of this invention. Such suitable means include but are not limited to flexographic printing, equipped with thermal UV and/or EB curing stations which follow the printing station. Thus when the enεrgy curablε ink is frεe of a photoinitiator it may bε curεd by actinic radiation which is a beam of εlectrons . Alternativεly, when the energy curable ink contains a polymerization initiating system, it may be cured by actinic radiation which is UV radiation. The printed energy curable ink containing a polymerization initiating syεtem may be initially subjεcted to UV radiation and subsequently to a beam of electrons or thermal energy to complete thε curε . As usεd herein, thermal energy is intended _c include radiant energy such infrared or microwave energy and the like; or conductive thermal energy such as that produced by a heated platen or hot air oven, for example. The following examples illustrate specific aεpects of the present invention and are not to limit the scope thereof in any rεspεct and εhould not bε so construed. In thε following examples all percεntagεs providεd are in volumε pεrcεnt unless othεrwise noted. Example 1 An energy curable, cationic ink formulation was formulated using a modified Pigment Blue 15.4 composition containing copper phthalocyanine blue pigment and rheological additive. A rheological additive was prepared by charging a presscakε, containing 210 parts by wεight of coppεr phthalocyanine sulfonyl chloride (which may bε prεparεd by any convεntional method) into a mixture of 692 parts by weight of a primary amine-terminatεd poly (ethylene oxide/propylene oxide) (5/95) copolymer having a number average molecular weight of approximately 2,000 (available as XTJ 507 from the Huntsman Corporation) and 66 parts by weight of sodium carbonate and mixed. The final reaction mixture was then heated to 80-90°C under vacuum to remove water and produce the copper phthalocyanine additive. The modified Pigment Blue 15.4 composition was prepared by combining 12 % by weight of the copper phthalocyanine derived rheological additive where P is the residue of copper phthalocyanine with 79% by weight of conventional Pigment Blue 15.4 during the attrition procεss εtep of the conventional pigment. The energy curable, cationic ink was formulated from the follcwinc components. COMPONENTS WEIGHT % Cyracure ® 6110 <al 15 Modified Pigment Blue 15.4 5 CD 1012 ( ) 2 Irgacure* 261 (f) .5 DVE 3 ,9 ' 76 PE wax (d) 1 DC 57 (e) .5 (a) Cyracure * 6110, available from the Union Carbide Corporation, Boundbrook, NJ is 3 , -epoxycyclohexylmethyl -3, 4 epoxycyclohexylcarboxylate; (b) CD 1012, available from the Sartomer Corporation, Exton, PA, is diaryliodonium of hexaf luoroantimonate; (d) PE wax, available from the Shamrock Corporation, Newark, NJ is polyethylene wax,- and (e) DC 57, available from the Dow Chemical Corporation, Midland, MI, is silicone additive. (f) Irσacure * 261, available from the Ciba Corporation, White Plains, NY, is {n 5 -2 , 4-cyclopentadien-l-yl) [ (1, 2 , 3 , 4 , 5 , 6-N) (1 -methyl ethyl) benzene I-iron-hexaf luorophosphate; and (g) DVE, available from the GAF Corporation, is triethyleneglycol divinyl ether. The Cyracure* 6110 and thε modified Pigment Blue 15.4 werε mixed at high speεd (about 2000 rpm) with a Cowles blade and then processed through a media mill containing 1 mm size media. After processing, the remaining components were added and the viscosity of the two inks were measured. PIGMENT VISCOSITY ® 25°C Modified PB-15.4 20+5 cps at 240 s-1 Conventional PB-15.4 100±20 cps at 240 s-1 Printing runs werε carriεd out with a gravurε hand- proofer (available from Pamarco Inc.) Thε major εlεments of thε gravurε hand-proof er are: a 300 line/inch (118 line/cm) anilox roller; and a doctor blade assεmbly for regulating the ink supplied to the anilex roller. The printed samples werε passε through a UV curing unit, (available from R.P.G. Industries) having a lamp with an output of 400 Watts/inch in the UV spectral region arid a cylindrical reflεctor. Thε subεtratε which was printεd was the polyester label film from Fasson. The printing speed was about 1 m/sec (200 ft/min) Using modified Pigment Blue 15.4 ink composition, a uniform ink film was applied to the substrate with the hand proofer and cured with this curing unit. A cured uniform ink film was likewise printed using conventional Pigment Blue 15.4 ink composition. Color density and gloss measurements as described in Example 1 were carried out with thε modified and the conventional Pigmεnt Blue 15.4 prints. The asseεsεd quality using the two ink formulations were: PIGMENT COLOR DENSITY GLOSS 60° Modified PB-15.4 1.4 90 Conventional PB-15.4 1.1 70 The ink containing modified Pigment Blue 15.4 demonstratεs morε uniform lay and lεsε rεticulation than the ink containing the conventional pigment, which rεsults in highεr density and better gloss of the print. Example 2 An energy curablε, cationic ink formulation was formulated using a modified Pigment Violet 23 composition containing Pigment Violet 23 and rheological additive. Modified Pigment Violet 23 composition was prepared by combining 15 % by weight of the copper phthalocyanine derivεd rheological additive of Example 1 with 85% by weight of conventional Pigment Violet 23 during the attrition process step of the conventional pigment. The enεrgy curable, cationic ink was formulated from the following components. COMPONENTS WEIGHT % Cyracure ® 6110 26 Modified Pigment Violet 23 8 E6250 60 CD 1012 5 PE wax 1 DC 57 .5 (h) E6250 , available from the Hϋls America Corporation, Somerset, NJ, is (2- (3 , 4 -epoxycyclo hexyl) ethyltrimethoxysilane) . The Cyracure* 6110 and the modif ied Pigment Violet 23 were mixed at high speed (about 1000 rpm) with a Cowles blade and then processed through a media mill containing 1 rvm size media . After Procεssing the remaining components were added and the viscoεity of the two inks were measurεd . PIGMENT VISCOSITY @ 25°C Modif ied PV-23 20±5 cps at 240 s "1 Conventional PV-23 150±50 cps at 240 s " 1 Printing runs, as describe in Example 1, were carried out with the modified Pigment Violet 23 and compared to conventional Pigment Violet 23. Color density and gloss measurements were carried out with the modified and conventional Pigment Violet 23 prints. The assessed quality using the two ink formulations were: PIGMENT COLOR DENSITY GLOSS 60° Modified PV-23 2.34 75 Conventional PV-23 1.88 46 Example 3 A UV curable ink jet ink was formulated using a modified Pigment Black 7 composition, prepared by dry mixing 19 wt . % of copper phthalocyanine rheological additive as describεd in Example 1 and 81 wt . % of a conventional Black Pigment 7 and adding the following components : Components Weight % Cyracure * 6105 ( ) 15 Modified Pigment Black 7 5 Limonene Dioxide 75 UVI 6974 (b) 5 (a) Cyracure 6105, available from the Union Carbide Corporation, is 3 , 4epoxycyclohexylmethyl-3 , 4 epoxycyclohexylcarboxylate; and (b) UVI 6974, available from the Union Carbide Corporation, is triarylsulphonium hexafluoroantimonate . The Cyracure 6105 and the modified Pigment Black 7 were mixed together in a ratio of 3:1. After processing, the remaining components were added slowly at low mixing speεd. The reεulting ink was subjected to a set of physical tests, i.e. viscosity measurεments at 25°C and 100 s *1 , a thermal stability test and optical microscopy for pigment dispersion. The thermal stability test consists of a rheological profile (viscosity vs. time) of the ink, obtained by shearing the sample constantly at 100 s "1 and at temperatures from 25°C to 80°C and back to 25°C. If the viscosity-tempεrature profile on thε upward curve and thε downward curvε match exactly, thermal stability is good. Any other behavior is an indication of irreversiblε pigmεnt flocculation. The 25°C viscosity at 100 s "1 was 14 mpa.s, which is fine for several ink jet hεads. Thε thermal stability was good. Optical microscopy showed a very fine dispersion with no particles above one micron. A draw down was done on coated paper, aluminum foil and on a corona treated polyethylenε film, with a #3 Mεyεr Rod. Thε rεsulting ink lays wεrε curεd at 200 fpm, with 2 lamps having an output of 300 Watts/inch in thε UV spεctral region and a cylindrical reflector. The ink layers were fully cured and exhibitεd good adhεsion on both substratεs, good rεsistance to watεr and good scratch resistance. The ink jet ink was filled in the DOD printer head and jetted at room tempεraturε onto a coatεd paper, a film and aluminum foil. The ink jεttεd finε and dot addrεssability was εxcεllεnt. Thε rεsulting printed substrateε were cured under thε same conditions as the draw downs and εxhibitεd thε samε rεsistance propεrties . Examolε 4 A UV curablε ink jet ink formulation was formulated using a modified Pigmεnt Bluε 15:4 composition prεparεd by according to Examplε 1. The following components werε then addεd: Componεnts Wεight % Cyracure* 6105 <a) 11.9 Modifiεd Pigmεnt Phthalocyaninε Bluε 15:4 5.1 Limonεne Dioxide 78 UVI 6974 (b) 15 (a) Cyracure 6105, available from the Union Carbide Corporation, is 3 ,4epoxycyclohexylmethyl-3, 4 epoxycyclohexylcarboxylate; and (b) UVI 6974, available from the Union Carbide Corporation, is triarylsulphonium hexafluoroantimonate. ^ D PCΪ7US99/27038 The Cyracurε 6105 and the moditied Pigment Phthalocyanine Blue 15:4 werε mixed together in a ratio of 7:3. After processing, the remaining components were added slowly at low mixing speed. The resulting ink was subjected to the samε set of physical tests as in Example 3. The 25°C viscosity at 100 ε "1 was 13 mPa.s, which is fine for several ink jet heads. The thermal stability was good. Optical microscopy showed a very fine dispersion with no particles above one micron. Draw downs werε donε on aluminum foil, corona treated polyethylenε and polypropylenε films, a chεmically trεatεd polyester film, a PVDC coated cellophane and on metallized polypropylene film, with a #3 Meyer Rod. The ink lays were cured at 200 fpm, with 2 lamps having an output of 300 Watts/inch in the UV spεctral rεgion and a cylindrical reflector. The cured ink lays exhibited good adhesion on every substrate cited except on chemically treated polyestεr film, good rεsistance to watεr on every substrate except on corona treated polyethylene film and good scratch resistance on every substrate except on metallized polypropylene film. Example 5 A UV curable ink j et ink formulation was formulated using a modified Pigment Black 7 composition as described in Example 3 , and the following components : Components Weight % Siloxane S -200 (a) 14 Modified Pigment Black 7 6 Z-6040 (b) 75 UVI 6974 (c) 5 (a) Siloxane S -200 , experimental product available from Rhone- Poulenc, Cranbury, NJ, 1 , 3Bis (2 - ( 7 -oxabicyclo ( . 1 . 0 ) hept-3 - yl) ethyl) -1,1,3, 3-tetramethyldisilcxane; (b) Z-6040, available from Dow Corning, Midland, MI, is glycidcxy-methoxy silane and vc) UVI 6974, available from the Union Carbide Corporation, is triarylsulphonium hexafluoroantimonate . The Siloxane S-200 and the modified Pigment Black 7 were mixed togethεr in a ratio of 4:6. Aftεr processing, the remaining components were added slowly at a low mixing speed. The rεsulting ink was subjεcted to thε samε sεt of physical tests as in Example 3. The 25°C viscosity at 100 s-1 was 5 mPa.s, which is fine for several ink jet heads. The thermal stability waε good. Optical microεcopy showed a very fine dispersion with no particles abovε one micron. Draw downs were done on aluminum foil, corona treated polyethylene and polypropylene films, a chemically treated polyester film, a PVDC coated cellophane and on metallized polypropylene film, with a #3 Meyer Rod. The resulting ink lays were cured at 200 fpm, with 2 lamps having an output of 300 Watts/inch in the UV spectral region and a cylindrical reflectors The cured ink lays exhibited good adhesion on every substrate cited above except on chemically treated polyester film, good resistance to water on every substrate except on mεtallized polypropylenε film wherε it was fair, and good scratch rεsistance on every substrate except on metallized polypropylene film where it was fair. The ink jet ink was filled in the DOD printer head and jetted at room temperature onto a coated paper, a film and aluminum foil. The ink jetted fine and dot addressability was excεllεnt. Thε rεsulting printed substrates wεre cured under the same conditions as the draw downs and exhibited the same resistance properties. Examplε 6 A UV curable ink jεt ink formulation was formulated using a modified Pigment Black 7 composition as dεscribed in Example 3, and the following components: Components Weight % Cyracure 6105 ('a) 18 . 6 Modifiεd Pigment Elack 7 5 . 9 Z-6040 tb) 70 . 5 UVI 6974 (c) 5 (a) Cyracure 6105, available from the Union Carbide Corporation, is 3 , epcxycyclohexylmethyl-3, 4 epoxycyclohexylcarboxylate ; (b) Z-6040, available from Dow Corning, is glycidoxy-methoxy silane; and (c) UVI 6974, available from the Union Carbide Corporation, is triarylsulphonium hexafluoroantimonate . The Cyracure 6105 and the modified Pigment Black 7 were mixed together in a ratio of 4:6. After processing, the remaining components werε added slowly at slow mixing speed. The resulting ink was subjectεd to thε εamε set of physical tests as in Example 3. The 25°C viscosity at 100 s "1 was 8.5 mpa.s, which is fine for several Ink Jet heads. The thermal stability was good. Optical microscopy showed a very fine dispersion with no particles above one micron. Draw downs were done on aluminum foil, corona treated polyethylene atid polypropylene films, a chemically treatεd polyester film, a PVDC coated cεllophane and on metallizεd polypropylene film, with #3 Meyer Rod. The resulting ink lays were cured at 140 fpm, with 2 lamps having an output of 300 Watts/inch in the UV spectral region and a cylindrical reflector. The cured ink lays exhibited good adhesion on every substrate cited above except on chemically treatεd polyεstεr film whεrε it was poor, good rεsistance to water on every substrate except on metallized polypropylenε film whεre it was fair to poor, and good scratch resistance or. every substrate except on metallizεd polypropylεnε film wherε it was fair to poor. Example 7 A UV curablε ink jet ink formulation was fcrmulatεd using a modifiεd pigment Black 7 composition as described in Example 3, and the following components: Components Weight % Flexol Φ L0E (a) 9 . 5 ERLX 4683 (bl 1 . 7 Modified Pigment Black 7 4 . 8 Limonene Dioxide 39 Z - 6041 (c) 40 UVI 6974 (dl 5 (a) Flexol LOE, available from the Union Carbide Corporation, is an epoxidized linseed Oil (oxobis ( l-butane-2 , 2 -dimethylol) ; (b) ERLX 4683 is an experimental product available from the Union Carbide Corporation and is tetrakis (3 , 4-epoxycyclohexane- carboxylate) ; and (c) Z-6041 is an experimental product available from Dow Corning and is glycidoxy-ethoxy silane ; and (d) UVI 6974 , available from the Union Carbide Corporation, is triarylsulphonium hexaf luoroantimonate . The Flexol LOE, the ERLX 4683 and the modified Pigment Black 7 wεrε mixed together in a ratio of 20 parts of Flexol LOE, 3.5 parts of ERLX 4683 and 10 parts of modified Pigment Black 7. After processing, the remaining components were added slowly at low mixing speed. The resulting ink was subjected to the same set of physical tεsts as in Example 3. The 25°C viscosity at 100 s "1 was 7.5 mpa.s, which is fine for several ink jet heads. The thermal stability was good. Optical microscopy showed a very fine diεperεion with no particles above one micron. Draw downs were done on aluminum foil and corona treated polyethylene with a 3 Meyer Rod. The resulting ink lays were cured at 200 fpm, with 2 lamps having an output of 300 Watts/inch in the UV εpectral region and a cylindrical reflector. The cured ink layε exhibited good adhesion, good resistancε to watεr and good scratch rεsistance on both substrates. Example 8 A UV curable ink jet ink formulation was formulated using a modified Pigment Yellow 12 composition. The modified Pigmεnt Yεllow 12 composition containing Pigment Yεllow 12 and rheological additive was preparεd as described in Examplε III of U.S. Patεnt 5,062,894. A mixturε of 16.5 parts of isatoic anhydridε (96% purε) and 220 parts of a primary amine-terminated poly (ethylene oxide/propylene oxide) (70/30) copolymer having a number average molεcular wεight of approximately 2,000 (available from Huntsman Corporation) was stirred and heated gradually to 80°C until evolution of C0 2 ceasεd. Thε infrarεd spεctrum indicated that thε isatoic anhydridε had completely reactεd as εvidεnced by the disappearancε of thε charactεristic anhydridε absorptions at 1748 cm- 1 . Thereafter, 16.5 parts of t-butyl acetoacetate were added and the reaction mixture was heated at 95°C and stirred for 8 hours to form Agent 1. Tetrazotizεd 3,3' O-dichlorobenzidine (DCB) was then prepared by adding 21.7 parts DCB to 39.8 parts of 200 Be hydrochloric acid and 140 parts of ice/water mixture with constant stirring to form a homogenous suspension. 32.6 parts of a 38% solution of sodium nitrite was added to the suspension and stirring was continued for 1 hour 0- 3°C . The excess nitrous acid was then destroyed by the 5 addition of approximately 0.5 part sulfamic acid. A fine suspension of coupler was prepared by charging 31.1 parts acetoacetanilide and 0.5 part phenylmethyl pyrazoione (a shading agent) to 4DC parts water and 33.6 parts of 50% sodium hydroxide. The mixture was stirred 0 until all solids werε dissolved, then the temperature was adjusted between 0 and 5°C and thereafter the coupler was precipitated by slowly adding 36.2 parts of 70% acetic acid. Immediately prior to coupling, 20.6 parts of Agent 1 were added to the coupler suspension as stirring was 5 maintained throughout coupler preparation and reaction. Coupling was then carried out by adding the solution of tetrazotized DCB to the fine suspension of coupler over a 40 minute period while stirring until no excess tetrazotized DCB remained. Then the temperature was o increased to 40°C. The resulting pigment slurry was stirred an additional 30 minutes, filtered, washed and dried in an oven at 75°C. (Yield 69 parts of Modified Pigment Yellow 12 composition containing Pigment Yellow 12 and rheological additive) . The following components 5 were added: Components Weight % Cyracure 5 6105 (a) 30 Modif ied pigment Yellow 12 5 Z -6040 (b) 60 UVI 6974 (c) 5 (a) Cyracure 6105 , available from the Union Carbide Corporation, is 3 , 4epoxycyclohexylmethyl-3 , 4 epoxycyclohexylcarboxylate; (b) Z-6040 , available from Dow Corning, is glycidoxy-methoxy silane ; (c) UV ' 6974 , available from the Union Carbide Corporation, is triaryl -sulphonium hexaf luoroantimonate . The Cyracure 6105 and the modified Pigment Yellow 12 were mixed together in a ratio of 3:1. After processing, the remaining components were added slowly at low mixing speed. The resulting ink was subjected to the same set of physical tests as in Example 3. The 25°C viscosity at 100 ε "1 was 12 mpa.s, which is fine for several Ink Jet headε . The thermal stability was good up to 50°C. Optical microscopy showεd a vεry fine dispersion with no particles above one micron. Draw downs werε donε on aluminum foil and corona treated liolyethylεnε with a #3 Meyεr Rod. Thε rεsulting ink lays wεrε cured at 200 fpm, with 2 lamps having an output of 300 Watts/inch in the UV spεctral rεgion and a cylindrical reflector. The curεd ink layε exhibited good adhesion, good resistance to water and good scratch resistance on both substrates. Example 9 A thermal curablε ink jεt ink formulation was formulated using a modified Pigment 3lack 7 composition according to Example 3, and the following components: Components Weight % Cyracure* 6105 (a) 14 Modified Pigment Black 7 6 Limonene Dioxide 75 TLC 14-12 (b) 2.5 Propylene Carbonate 2.5 (a) Cyracure 6105, available from the Union Carbide Corporation, is 3 , epoxycyclohexylmethyl-3 , 4 epoxycyclohexylcarboxylate; and (b) TLC 14-12, experimental product available from King Industries, is a blocked acid. The Cyracure 6105 and the modified Pigment Black 7 were mixed togethεr in a ratio of 3:1. The thermal initiator, TLC 14-12, was dissolved in Propylene Carbonate in a ratio of 1:1. After processing, thε Limonene Dioxide was added slowly at low mixing speεd, followed εhortly by the addition of the thermal initiator solution. The rεsuiting ink was subjected to the same set of physical tests as in Examplε 3, εxcept thε thεrmal stability test. Thε 25°C viscosity at 100 s '1 was 14 mPa.s, which is finε for εeveral ink jet heads. Optical microscopy showed a very fine dispersion with no particles above one micron. Draw downs were done on aluminum foil and on coated paper with a #3 Meyer Rod. The resulting ink lays werε -cured in an oven at 140°C for 45 s or 160°C for 15 s. The cured ink layε exhibited good adhesion, good resistancε to water and good scratch rεεiεtancε on both εubεtrateε. The ink jet ink waε filled in the DOD printer head and jettεd at room tempεraturε onto a coatεd paper, a film and aluminum foil. The ink jetted fine and dot addressability was excellent. The resulting printed substrates werε cured under the same conditions as the draw downs and exhibited the same resistancε propεrtieε. Example 10 A thermal curable ink jet ink formulation was formulated using a modified Pigment Black 7 composition according to Example 3, and the following componentε: Components Wεight % Cyracure* 6105 (a) 14 Modified Pigment Black 7 6 Limonene Dioxide 75 FC- 520 (b) 5 (a) Cyracure 6105 , available from the Union Carbide Corporation, is 3 , 4epoxycyclohexylmethyl-3 , 4 epoxy - cyclohexylcarboxylate; and (b) FC-520 , available from 3M, St . Paul , MN, is a blocked f luoroaliphatic acid salt . The Cyracure 6105 and the modified pigment black 7 werε mixed together in a ratio of 3:1. After processing, the Limonene Dioxide was added slowly at low mixing speεd, followed shortly by thε addition of the FC-520 thermal initiator. The resulting ink was subjεctεd to phyεical testing. The 25°C viscosity at 100 s "1 was 14 mpa.s, which is fine for several ink jet heads. Optical microscopy showed a very fine disperεion with no particlεs above onε micron. Draw downs were done on aluminum foil and on coated paper with a #3 Meyεr Rod. Thε rεεulting ink lays were cured in an oven at 140 °C for 60 s or 160 °C for 30 s. The cured ink lays exhibitεd good adhεsion, good resistance to water and good scratch resiεtance on both substrates. Example 11 A thermal curable ink j et ink formulation was formulated using a modified Pigment Black 7 composition according to Example 3 , and the following components : Components Weight % Cyracure* 6105 (a) 24 Modified Pigment Black 7 6 Z-6040 <b) 65 TLC 14-12 (c) 2 . 5 Propylene Carbonate 2 . 5 (a) Cyracure 6105 , available from the Union Carbide Corporation, is 3 , 4epoxycyclohexylmethyl -3 , 4 epoxy- cyclohexylcarboxylate; (b) Z-6040 , available from Dow Corning, is glycidoxy-methoxy silane ; and (c) TLC 1412 , experimental product available from King Industries , is a blocked acid. The Cyracure 6105 and the modified Pigment Black 7 werε mixed togethεr in a ratio of 4:6. The thermal initiator, TLC 1412, was disεolvεd in propylene carbonate in a ratio of 1:1. After proceεεing, the remaining Cyracure 6105 and thε Z-6040 wεrε added slowly added at low mixing speed, followed shortly by the addition cf the thermal initiator εolution. The rεεulting ink waε εubjεcted to phyεical testing. The 25°C viscosity at 100 s "1 was 10 mpa.s, which is fine for several Ink Jet heads. Optical microscopy showed a vεry fine dispersion with no particles above one micron. Draw downs were done on aluminum foil and on coated paper with a #3 Meyer Rod. The resulting ink lays were cured in an oven at 160°C for 15 s. The cured ink layε exhibited good adhesion, good resistance to water and good scratch resiεtance on both εubεtrates. Example 12 A thεrmal curablε ink j εt ink formulation was formulated using a modified Pigment Black 7 composition according to Example 3 , and the following components : Components Weight % Siloxane S-200 (al 14 Modified Pigment Black 7 6 Z- 6040 (b) 75 TLC 14- 12 ,c) 2 . 5 Propylene Carbonate 2 . 5 (a) Siloxane S-200 experimental product available from Rhone- Poulenc , 1 , 3Bis (2- (7 -oxabicyclo (4 .1.0) hept -3 -yl) ethyl) -1 , 1 , 3 , 3 - tetramethyldisiloxane; (b) Z-6040 , available from Dow Corning, is glycidoxy-methoxy silane,- and (c) TLC 1412 , experimental product available from King Industries , is a blocked acid. The Silane S-200 and the modifiεd Pig εnt Black 7 wεre mixed together in a ratio of 4 : 6 . The thermal initiator, TLC 14-12, was disεclved in Propylεnε Carbonatε in a ratio of 1:1. Aftεr proceεεing, the remaining Cyracure 6105 and the Z-6040 werε added εiowly at low mixing εpεed, followed εhortly by thε addition cf the thermal initiator solution. The rεsulting ink was subjεcted to physical testing. The 25°C viscosity at 100 s "1 was 5 mPa.s, which is fine for sεveral ink jet heads. Optical microscopy showed a very fine dispersion with no particles above one micron. Draw downs were done on aluminum foil and on coated paper with #3 Meyεr Rod. Thε resulting ink lays wεrε curεd in an ovεn at 160°C for 15 s. The cured ink lays exhibited good adhesion, good resistance to water and good scratch reεistance on both subεtrateε. The ink was filled in the DOD printer head and jettεd at room temperature onto a coated paper and aluminum foil. The ink jetted fine and dot addressability was excεllen . Tables I, II and III summarize the formulations and resulting physical propertiεs for ink jεt inks prεparεd according to a fεw Examplεs and other ink jet inks prepared in accordance with the present invention. The inks were jetted onto coated paper substrateε . TABLE TABLE II TABLE Thoεe εkilled in the art having the benefit of the teachings of the presεnt invention as herεinabove set forth, can effect numerous modifications thereto. These modifications arε to bε construεd as bεing εncompassed within thε scope of the present invention as sεt forth in thε appended claims .

Claims: 5 What is claimed is: 1. An energy curable gravure ink comprising: a pigment; a rheological additive having the structure: 0 P-(U-Y). wherein P is the residuε of an organic colorant, Y is a polyalkylεne oxide moiety, U is a linking moiety covalently bonding Y to P, and s iε an integer from 1 to 5 3 and; an energy curable liquid vεhiclε; whεrεin thε ink is substantially frεε of fugitive solvent and has a viscosity ranging from about 8 cps to about 200 cps. 2. The ink of claim 1 wherεin the polyalkylene oxide moiety is an ethylene oxide polymer. 0 3. The ink of claim 1 wherein the polyalkylene oxide moiety is an ethylenε oxidε/propylene oxide copolymer. 4. The ink of claim 3 wherein the copolymer has the genεral formula: Q' -O- (CH.CHO) n -CH 2 CH- I I Q Q wherein n is about 4 to about 400; Q iε H, CH 3 or a combination therεof; and Q 1 iε a C_-C 6 alkyl moiety. 5. The ink of claim 4 wherein n is about 4 to 35 about 60. 6. The ink of claim 1 wherein P is a residuε of an azo pigmεnt, phthalocyanine pigment, dioxazine pigment, quinacridone pigment, perylene pigment, or perinonε pigmεnt . 7. Thε ink of claim 1 whεrεin U is a covalent bond, or a multivalent moiety selected from the group consisting of Ci-C_ alkyl, -NHS0 2 -, -0-, -CO-, -COO-, -N=, and -COH-. 8. The ink of claim 1 whεre s haε the value 1 or 2. 9. The ink of claim 1 wherein the rheological additive iε an azomethine having the general formula: whεrεin Y is the alkylene oxide polymer containing about to about 200 groups; R and R 1 are indepεndently selectεd from the group consisting of H, CH 3 , OCH . , OCH 2 CH 3 and Cl ; n is an integer from 1 to 5; X is selectεd from the group consisting of Ci, CH 3 , and OCH 3 ; and Z iε selected from the group consisting of 0 and N-Y. 10. The ink of claim 1 wherein the additive is an azomethine having the genεral formula: wherein Y is the polyalkylene oxide polymer containing about 4 to about 20 repeat units; R 1 is H, CH 3 , OCH 3 OCH 2 CH 3 or Cl ; n is an integer from 1 to 5; R 2 iε CH 3 or COOCH 2 CH 3 ; R 3 is H or CH 3 ; and XI is Cl or OCH 3 . 11. The ink of claim 1 wherein the additive is a diarylide having the general formula: wherein: R 4 and R s are independently selected from the group consisting of Cχ-C4 - alkyl, C.-C4 alkoxy, and halogen; m and p are independεntly intεgers of 0 to 5; X 2 is selected from the group consiεting of C_, CH 3 , and OCH 3 ; U 2 compriεeε a divalεnt bridging moiεty εelεcted from the group conεisting of C_-Cs alkyl, -NHSO 2 - , -0- , -CO-, -COO-, and -C NH-; Y 1 comprises the polyalkylene oxide moiety having a numbεr avεrage molecular weight of about 200 to 10,000; and k and 1 are independently integers of 0 or 1, with the proviso that for at least 50 wt . % of the pigmεnt composition, k and 1 arε both εqual to 0, and for at least 3 wt . % of the pigment composition 5 k and/or 1 are equal to 1. 12. Thε ink of claim I wherein the additive ε an azomethine having the general formula: wherein Y is the polyalkylene oxide polymer containing about 4 to about ' 20 repeat units; R6 is independently selected from the group consisting of Cl , OCH 3 , CH 3 , OC 2 H b , C 2 H 5 , and CONH 2 ; R 7 is independently selected from the group conεiεting of Cl , OCH 3 , CH 3 , NO^, OC 2 H 5 , C 2 H 5 , CONH 2 , SO 3 H, OH and COOH; and a and b are indεpendently integers of 0 to 5. 13. The ink of claim 1 wherein the additive is a phthalocyanine having the general formula: wherεin Y has thε general formula: Q'-0-(CH_CHO)_-CH_CH- I I Q Q to whεrεin n is about 4 to about 400, and a, b, c and d are integεrs indεpεndεntly from about 0 to about 4, providεd at least one of them iε 1; Q is H, C-i-. or a combination thεreof; and Q' iε a Cι-C_ alkyl moiety. 14. The ink of claim 1 wherein the pigment is εelectεd from thε group consisting of Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigmεnt Yellow 13, Pigment Yellow 14, Pigment Yellow 17, Pigment Yεllow 37, Pigment Yellow 63, Pigment Yellow 65, Pigment Yellow 73, Pigmεnt Yellow 7 4, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 97, Pigmεnt Yellow 98, Pigment Yellow 106, Pigment Yellow 114, Pigment Yellow 121, Pigmεnt Yεllow 126, Pigment Yellow 127, Pigment Yellow 136, Pigment Yellow 174, Pigment Yellow 176, Pigmεnt Yεllow 188, Pigment Orange 5, Pigmεnt Orangε 13, Pigment Orange 16, Pigment Orange 34, Pigment Red 2, Pigment Red 9, Pigment Red 14, Pigment Red 17, Pigment Red 22, Pigment Red 23, Pigment Red 37, Pigment Red 38, Pigmεnt Red 41, Pigmεnt Rεd 42, Pigment Red 112, Pigment Red 146, Pigment Rεd 170, Pigmεnt Rεd 196, Pigment Red 210, Pigment Red 238, Pigment 3lue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigment Blue 15:3, Pigment Blue 15:4, Pigmεnt Grεεn 7, Pigmεnt Green 36, Pigment Violet 23, and Pigment Black 7. 15. The ink of claim 1 wherεin thε pigment is distinct from P. 16. Thε ink of claim 1 whεrεin thε pigment is the same as P. 17. The ink of claim 16 wherεin thε ink contains an additional distinct pigment. 18. The ink of claim 1 wherein the enεrgy curable liquid vehiclε is a ring opεning polymεrizable composition. 19. The ink of claim 18 wherein the polymerizable composition is a cationic polymerizable system comprising one or more mono- functional and/or multi-functional epcxidε monomεrs . 20. The ink cf claim 19 wherein the cationic polymerizable composition comprises a cycloaliphatic epoxide . 21. The ink cf claim 20 wherein the cycloaliphatic epoxide is selected from 3 , 4-epoxycyclohexyimethyl 3,4- epoxycyclohεxylcarbcxylatε and 1 , 3 -bis (2- (7-oxabicy- clo(4.1.0)hepta-3-yi)ethyl) -1, 1 , 3 , 3 -tεtramethyl- diεiloxane . 22. The ink of claim IS wherein the cationic polymerizablε compoεition comprises a non-cycloaliphatic epoxide . 23. The ink of claim 22 wherein the non- cycloaliphatic epoxide is selected from glycidoxy-methcxy εilanε and glycidoxy-εthoxy εilane. 24. Thε ink of claim 18 furthεr compπεing a polymerization initiating εyεtem activatable by actinic radiation. 25. The ink of claim 24 wherein the polymerization initiating system employs a thermal and cationic initiator. 26. The ink of claim 1 wherein the energy curable liquid vehiclε is a frεe radical addition polymεrizablε systε comprising an ethylεnεically unsaturated monofunctional or multi-functional monomer. 27. The ink of claim 26 wherεin the ink contains a freε radical gεnεrating, addition polymerization initiating system activatable by actinic radiation. 28. Thε ink of claim 1 wherein the ink contains a surface active agent, a wax, or a combination thereof. 29. A method of gravure printing and curing a gravure ink comprising the steps of: (a) preparing an energy curable gravure ink having a pigment and a rheological additive of the structure : P- CJ-Y), wherein P is the residue cf an organic colorant, Y is a polyalkylene oxide mciεty, U s a linking mciεty ccvalεntly bonding Y to P , and ε is an integer from 1 to 3; and an enεrgy curable liquid vehicle; wherein the ink is substantially freε of fugitive solvent and has a viscosity ranging from about 8 cps to about 200 cps; (b) printing the ink on a substrate surface to form an image; and (c) subjecting the image to actinic radiation or thermal energy to form a cured image . 30. The method of claim 29 wherein the actinic radiation is a beam of elεctrons. 31. The method of claim 29 wherεin thε εnεrgy curablε ink contains a polymεrization initiating system activatable by actinic radiation, and wherein the actinic radiation is ultraviolet radiation. 32. The method of claim 29 wherein the image is subjected to ultraviolet radiation, a beam of elεctrons or thεrmal εnergy. 33. The method of claim 27 wherein the thermal energy is radiant or conductive thermal enεrgy. 34. A mεthod of ink jet printing and curing an ink jet ink comprising the steps of: (a) preparing an energy curable ink jet ink having a pigment and a rheological additive of the structure: P-(U-Y). wherεin P is the residue- of an organic colorant, Y is a polyalkylene oxide moiety, U is a linking moiety covalently bonding Y to P , and s is an integer from 1 to 5 3; and an energy curable liquid vehicle; wherεin the ink is subεtantially free of fugitive solvent and has a viscoεity ranging from about 3 cps to about 20 cps; (b) printing the ink on a substrate surface to form an image; and ιo (c) εubjecting thε imagε to actinic radiation or thermal energy to form a cured image . 35. The method of claim 34 wherein the actinic radiation is a beam of electrons. 36. The method of claim 34 wherεin thε energy 15 curable ink contains a polymerization initiating εyεtem activatablε by actinic radiation, and whεrεin thε actinic radiation is ultraviolεt radiation. 37 . Thε mεthod of claim 34 wherein the image is subjected to ultraviolet radiation, a beam of elεctrons 0 or thermal energy. 38. The method of claim 37 wherein the thermal energy is radiant or conductive thermal energy. 39. An energy curable ink jet ink comprising: a pigment; a rheological additive having the structure: 5 P- (U-Y) wherein P is the residue of an organic colorant, Y is a polyalkylene oxide moiety, U is a linking moiety 0 covalently bonding Y to P, and s is an integer from 1 to 3 and; an energy curable liquid vehicle; wherein the ink is substantially free of fugitive solvent and has a viscosity ranging from about 3 cps to about 20 cps. 40. The ink of claim 39 wherein the polyalkylene 5 oxide moiety is an ethylene oxide polymer. 41. The ink of claim 39 wherein the polyalkylene oxide moiety is an ethylene oxide/propylene oxide copolymer. 42. The ink of claim 41 wherein the copolymer has the genεral formula: 42. The ink of claim 41 wherein the copolymer has the genεral formula: Q'-0-(CH_CHO)„-CH_CH- I I Q Q whεrein n is about 4 to about 400; Q is H, CH 3 or a combination therεof; and Q 1 is a C_-C 6 alkyl moiety. 43. The ink of claim 42 wherein n is about 4 to 35 about 60. 44. The ink of claim 39 wherein P is a residue of an azo pigmεnt, phthalocyanine pigment, dioxazine pigment, quinacridone pigment, perylene pigment, or perinone pigmεnt. 45. The ink of claim 39 wherein U is a covalεnt bond, or a multivalent moiety selected from the group consisting of C_-C 6 alkyl, -NHS0 2 -, -O- , -CO-, -COO-, -N= , and -C0NH-. 46. The ink of claim 39 where s has the value 1 or 2. 47. The ink of claim 39 wherein the rheological additive is an azomethine having the general formula: wherein Y is the alkylene oxide polymer containing about to about 200 groups; R and R 1 are independently selected from the group consisting of H, CH 3 , OCH 3 , OCH 2 CH 3 and Cl ; n is an integer from 1 to 5; X is εelected from the group consisting of C_, CH 3 , and OCH 3 ; and Z is selected from the group consisting of 0 and N-Y. 48. The ink of claim 39 wherεin the additive is an azomethine having the general formula: wherein Y iε the polyalkylenε oxidε polymεr containing about 4 to about 20 rεpeat units; R 1 is H, CH 3 , OCH 3 OCH 2 CH 3 or Cl; n is an integer from 1 to 5; R 2 is CH 3 or COOCH 2 CH 3 ; R 3 is H or CH 3 ; and XI is Cl or OCH 3 . 49. The ink of claim 39 wherein the additive is a diarylide having the general formula: wherein: R 4 and R 5 are independently selected from the group consisting of Cι-C4 - alkyl, Cι-C4 alkoxy, and halogen; m and p are independεntly intεgers of 0 to 5; X 2 is selectεd from thε group consisting of C_, CH 3 , and OCH 3 ; U 2 comprisεs a divalεnt bridging moiεty sεlεctεd from the group consisting of C_-C 6 alkyl, -NHS0 2 - , -0- , -CO-, -COO-, and -CONH-; Y 1 comprises the polyalkylene oxide moiety having a number average molecular weight of about 200 to 10,000; and k and 1 are independently integεrs of 0 or 1, with the proviso that for at least 50 wt . % of the pigment composition, k and 1 are both equal to 0, and for at least 3 wt . % of the pigment composition 5 k and/or 1 are equal to 1. 50. Thε ink of claim 39 wherεin the additive is an azomethine having the general formula: wherein Y is the polyalkylene oxide polymer containing about 4 to about 20 repeat units; R6 is independently selected from the group consiεting of Cl , OCH 3 , CH 3 , OC2H5, C 2 H S , and C0NH 2 ; R 7 is independently selected from the group consiεting of Cl , 0CH_, CH 3 , N0 2 , 0C 2 H s , C 2 H 5 , C0NH 2 , SO3H, OH and COOH; and a and b are independently integers of 0 to 5. wherein Y has the general formula: Q' -O- (CH.CHO) n -CH_CH- I I Q Q to wherεin n is about 4 to about 400, and a, b, c and d arε intεgεrs indepεndεntly from about 0 to about 4, provided at least one of them is 1; Q is H, CH 3 or a combination thereof; and Q' is a C_-C 6 alkyl moiety. 52. The ink of claim 39 wherein the pigment is selected from the group consisting of Pigment Yellow 1, Pigment Yellow 3, Pigment Yellow 12, Pigmεnt Yεllow 13, Pigment Yεllow 14, Pigment Yellow 17, Pigment Yellow 37, Pigment Yellow 63, Pigment Yellow 65, Pigment Yellow 73, Pigment Yellow 74, Pigment Yellow 75, Pigment Yellow 83, Pigment Yellow 97, Pigment Yellow 98, Pigment Yellow 106, Pigment Yellow 114, Pigment Yellow 121, Pigment Yellow 126, Pigment Yellow 127, Pigmεnt Yellow 136, Pigment Yellow 174, Pigment Yellow 176, Pigment Yellow 188, Pigment Orange 5, Pigment Orange 13, Pigment Orange 16, Pigment Orange 34, Pigment Red 2, Pigment Red 9, Pigment Red 14, Pigment Red 17, Pigment Red 22, Pigment Red 23, Pigment Red 37, Pigment Red 38, Pigment Red 41, Pigment Red 42, Pigment Red 112, Pigment Red 146, Pigment Red 170, Pigment Red 196, Pigment Red 210, Pigment Red 238, Pigment Blue 15, Pigment Blue 15:1, Pigment Blue 15:2, Pigmεnt 3lue 15:3, Pigment Blue 15:4, Pigment Greεn 7, Pigment Green 36, Pigment Violet 23, and Pigment Black 7. 53. The ink of claim 39 wherein the pigment iε distinct from P. 54. The ink of claim 39 wherein the pigment is the same as P . 55. The ink of claim 54 wherεin the ink contains an additional distinct pigment. 56. The ink of claim 39 wherεin the energy curable liquid vehicle is a ring opening polymerizablε composition. 57. The ink of claim 56 wherein the polymerizable composition is a cationic polymerizablε systεm comprising onε or morε mono-functional and/or multi-functional εxpεctεd monomεrs . 58. Thε ink of claim 39 furthεr compriεing a polymerization initiating system activatable by actinic radiation. 59. The ink of claim 39 wherein the εnεrgy curablε liquid vεhiclε is a frεe radical addition polymerizable system comprising an ethylεneically unsaturated monofunctional or multi-functional monomer. 60. The ink of claim 59 wherein the ink contains a free radical generating, addition polymerizati_<n initiating systεm activatable by actinic radiation. 61. The ink of claim 39 wherein the ink contains a surface active agent, a wax, or a combination therεof.

Inventors: AURENTY PATRICE, CHATTERJEE SUBHANKAR, KOTORA GORDON, LAKSIN MIKHAIL, MERCHAK PAUL A, SCHWARTZ RUSSELL, STONE EDWARD, AURENTY, PATRICE, CHATTERJEE, SUBHANKAR, KOTORA, GORDON, LAKSIN, MIKHAIL, MERCHAK, PAUL, A., SCHWARTZ, RUSSELL, STONE, EDWARD
Applicants: SUN CHEMICAL CORP, SUN CHEMICAL CORPORATION
Application year: 1999
Main classification: C09B69
IPC codes: B41J2, B41M5, C09B67, C09D11