Title of Invention

"METHOD FOR WET TRAPPING WITH ENERGY CURABLE FLEXOGRAPHIC LIQUID INKS"

Abstract

The present invention is for a method whereby low viscosity llexographic printing inks having a viscosity controlling diluent are used in iinplenienting wet trapping of sequentially applied ink layers by controlling the time belvveen ink layer applications such that sufficient diluent evaporates froni an applied layers to increase the first applied layer viscosity sufficiently to wet trap a subsequent applied superimposed ink lay er.

Full Text

FIELD OF THE INVENTION This invention relates to a method and apparatus for flexographic colour printing and more particularly to the method and associated apparatus for implementing a method of wet trap printing also known as "wet trapping" in flexographic printing, using energy curable flexographic liquid inks. BACKGROUND OF THE INVENTION Multicolor impressions printing processes typically require the sequential printing of a plurality of superposed single color ink layers. When high quality image reproduction is desired, it is important to avoid a previously applied ink layer transferring back to a subsequent impression unit. Such transfer typically results in cross-contamination of colors and consequent undesirable color rendition. The art has addressed this problem in a number of different ways. The simplest way to prevent undesirable color contamination is to dry each applied ink layer prior to the application of a superposed next ink layer. While this method is effective it suffers a major disadvantage of requiring complete diying of the ink after applying each ink layer. Drying takes time and energy to accomplish, and as a result, productivity is reduced and production costs increase. In an effort to speed up the printing proecss. wet trapping was developed. I'nder the present invention, "wet trapping" is defmed as a process \vhereh\ liie ink layer deposited or applied at each inking station is not dried before the next ink layer is deposited there over to produce a coloristic or visual effect. 1 o iniplemenl wet trapping, it is important that the tack characteristics of the superpo.sed ink layers be manipulated so that they are different. Wet trapping is not a serious problem in offset printing, because the viseosit> of the inks used in offset printing ranges from 2().()()() to 100.000 cps. Such high viscosity inks inherently exhibit a wide range of lack characteristics that can be used to effect wet trapping without the need to dry the ink layers between the inking stations. In recent years, a form of printing that permits printing on various kinds ol substrates, that var) from cardboard to polyethylene to metal, has become widely accepted. This printing method is known as llcxography or tlexographic printing. I'lexography employs a resilient printing plate having raised portions, which are coated with an ink and pressed against a substrate to transfer the ink to the subslrale. In llcxography. ink is transferred from a reservour to the printing plate's raised surface through an intermediate transfer roll known in ihe arl as an anilox roll, I he anilox roll surface is covered by a plurality of tiny ink wells that fill with ink from the reservoir and transfer it lo the fiexogrtiphic printing plate. Obviously high ciuality printing requires that the tlexographic printing plate surface be inked uniformh and consistently. 1 his in turn requires that the anilox roll cells be small and that all of the anilox cells be filled each time with ink from the reservoir to substantially the same level. Such requirement poses limitations on the fluidity or viscosity olthe ink. A viscous ink will not be picked up as uniformly or consistently by the anilox roll and the (lexographic printing plate surface will not be inked uniformly, fhe result has been that inks suitable for Hexographic printing applications are liquid inks typically having viscosities under 2.000 cps. preferably less than 400 cps. Current regulations regarding solvent emissions have resulted in the development oi" printing inks suitable for use in llcxography that are energy curable. Such inks contain no solvent, and are fixed to the substrate not by drying but by curing via actinic radiation, such as ultraviolet light or electron beam, fhe tack of a Hexographic liquid ink is very low and cannot be adequately measured with conventional instruments, fheir \ iscosilies typically range from about 30 to 50 cps. While such viseositx range results in superior Hexographic printing, energy curable Hexographic liquid inks lor Hexographic applications exhibit very low tack, cannot be tack rated, and need lo be cured between inking stations to prevent back transfer and mixing iiom the printed ink on the substrate to the inking rolls of subsequent stations. Such inter-station curing is expensive, as it requires substantial equipment modification. Such curing is also undesirable from a manufacturing stand point, as it increases the time required between the deposition of a subsequent ink layer in order to allow for curing ol" (he previously deposited ink layer thereby slowing down the printing process. Wet trapping has also been proposed in non energy curable llexographic printing based on the recognition that when depositing superposed multiple layers of ink. cross-contamination will not occur if each layer is deposited over a layer having a higher viscosity than the newly deposited layer. The highest >iscosity layer traps, so to speak, the second layer without transferring the underlying la>er back to the impression unit. However, with the range of viscosities available I'or nexogiaphic printing inks, it is impractical to implement wet trapping using constantly decreasing ink \ iscosities in order to elTeet wet trapping, particularly as the number of applied layers increases. In essence. one runs out of available ink viscosities to implement vvel trapping. United States Patent 5.690.028 attempts to sohe the abo\e mentioned problem of limited available ink viscosity range by a method of wet trapping in a multicoktr printing application using energy curable inks, particularly suited lor a Central Impression llexographic Press. According to the patent the energy curable inks, are healed before being applied to a substrate, and are applied to the substrate at a teniperalure that is higher than the previously applied ink layer. Because the temperature of the pre\ iously applied ink layer on the substrate is cooler than the heated ink to be applied or super imposed, the viscosity of the previously applied ink layer is lower than the \iscosit> of the applied ink. This viscosity differential causes the lower \iscosity ink to unilaterally transfer onto the higher viscosity ink and prevents both back trapping and ink blending. While this method of wet trapping achieves the desired lesuil, it requires substantial modification to any existing printing press equipment to pro\ ide for healing units in each inking station belbre the ink is applied to the substrate, moreo\cr. as the number of stations increases, so must the ink temperature in the successive inking stations. Ihus. it may be necessary to apply cooling to the substrate, or the printing speed may have lo be reduced, in order to prevent having to increase the ink lemperature to levels thai nia> adversely alTeel its properties. Ihere is. therefore, still a need for a method to implement vvel trapping v\hen using energy curable tlexographic liquid inks where little or no modification of existing printing press equipment is required, yet still permitting higii speed throughout. SUMMARY OF THE INVENTION According to this invention, there is provided a method lor the llexographic printing of multiple superposed ink layers on a substrate using at least one energy curable llexographic liquid ink and printing a second similar ink of a different color there over without prit)r curing of the first printed energy curable ink. fhe method for applying the multiple ink layers on a substrate to effectuate wet Irapping comprises, in the following order : (a) applying onto a substrate at least one ink layer ol'an energy curable liquid ink having a viscosity of less than about 4()()() eps and comprised of a non reactive diluent, said applied energy curable ink layer having a first viscosity; (b) evaporating at least a portion of the non-reactive diluent in the applied ink layer, thereby increasing the viscosity of the applied energy curable ink layer: (c) applying onto said substrate and said applied energy curable ink layer ol increased viscosit>. at least one layer of a non-energy curable liquid ink having a viscosity lower than the increased viscosity of said pre\ iously applied energy curable ink layer; and (d) fixing both ink layers onto saitl substrate. According \o this invention, there is provided a method for printing multiple ink layers on a substrate, comprising selecting a lust and a second energy curable liquid nexographic inks, each containing a non-reactive diluent in an amount ol less than 50 wt. %. based on the weight of the diluent, each ink ha\'ing a viscosity under 4.()()() cps and preferably between about 30 and 70 cps, and sequentially applying the first and second energy curable liquid flexographic inks on a substrate to form first and second ink hners having superposed pe)rtions, wherein the second ink is applied after at least a portion of the non-reactive diluent in said first ink layer has been evaporated. fhere is also provided according to this invention apparatus for sequentiall\ applying multiple superposed ink layers on a substrate, at least one of the ink layers being an energy curable liquid ink containing a non reactive diluent and having a viscosity under 4000 cps. in a way to practice wet trapping, fhe apparatus comprises : (a) a substrate path and a substrate drive for driving said substrate along said predetermined path: (b) a plurality of ink applying stations spaced along said predetermined path, said ink applying stations adapted to apply an ink comprised ot a non-reactive diluent and having a viscosity less than 4000 cps onto said substrate; and (c) a control system for controlling said substrate transport along said path so that a first lic]uid ink layer, applied onto said substrate at one ol said inking stations, increases in viscosity through evaporation of at least some of said diluent from said llrst ink layer to a viscosity higher than a viscosity of a second ink applied o\er said fust ink layer in a subsequent inking station spaced from said first inking station, to a \isci)sity sufficient lo wet-trap said second liquid ink as said substrate is (ransporled between said inking stations. According to the present invention the steps ot sequentially printing ink layers may he repeated a number of times, using multiple sequential printings of energy curable inks, each time allowing at least a portion of the diluent in the printed layer to evajiorate and thereby have its viscosity increase, before printing the next layer of ink. further, and in accordance with the present invention, the in\'cntion is also a process of increasing the viscosity of an ink layer on the substrate by alknving al least a portion of the diluent in the printed energy curable ink layer to evaporate which process may be accelerated by the application of heat or by Ibrcing a stream of air over the inked surface between subsequent ink applications. BRIEF DESCRIPTION OF THE DRAWINGS Figure I shows a tlexographic printing press for wet trapping con.structed according to the present invention. Figure 2 shows an alternate embodiment of an apparatus for wet trapping in accordance with this invention, DETAILED DESCRIPTION OF THE INVENTION 1 he invention will next be described, where appropriate, with reference to the figures. Such figures are provided to facilitate an understanding of the invention, therefore, only such elements as are required for this understanding are illustrated and any equipment depicted is not drawn to scale nor is it intended to represent actual commercially used equipment. Ihe present invention relates to a novel process for wet trap printing of energ} curable liquid Hexographic inks in a llexographic printing environment, wherein the inks are preferably formulated, energy curable, aqueous, single phase. ct)mpositions. such as those of the type disclosed in co-pending Provisional U.S. Patent Application Serial Number 60/380081. filed May 6. 2002, entitled "Watcrbascd Single Phase F.nergy Curable Compositions", the full content of which is expressly incorporated herein by reference. Other, non-aqueous based compositions, luuing similar characteristics may also be used. In contrast to other Oexographic inks, the aqueous energ\ curable llcxographic liquid inks of the above-mentioned co-pending application lend to exhibit minimal tack change as they dry. however, they nonetheless exhibit viscosity changes sufllcicnt to crtectuate wet trapping on a llexographie press, as discussed below. rhese energy curable, single phase, ilexbgraphic liquid inks arc either single, ternary- of quaternary - compositions that contain a resin neutralizable by acid or base, and a non-reacti\'e diluent is used to control the viscosity of these inks. The single-pliase compositions suitable for printing under this invention are energy curable. The term "energy curable composition"", as used herein, is intended to mean compositions that are polymeri/able or cross linkable by the action of an energ\ source of actinic radiation, such as ultraviolet radiation (UV). radiation (EB). and the like. As used herein "ultraviolet radiation" is intended to encompass radiation ha\ ing a wavelength range rrom about 190 nm to about 500 nm. and i)ret'erably from about 200 nm to 420 nm. Actinic radiation of this type may be obtained from a variety i)f sources, e.g.. mercury arc lamps, xenon arc lamps, lluorescent lamps, monochromatic laser sources, and the like. lUectron beam radiation as used herein also is intended to encompass high-energy electrons, such as from electric discharge devices or eleciron beam devices typically operating at 70-200 kV and emitting a radiation in a typical range of 1-4 mRad. In one embodiment of ink compositions suitable for use in the present invention, the non-reactive diluent is water. However, compositions containing other non-reactive diluents. sueh as alcohol and mixtures ol" water and alcohol ma) be used, or any other suitable diluent offering volatility sulficient to permit enough of the diluent to evaporate within a reasonable time between the application oCconsecutive ink la>ers so that the \iscosity ol each applied ink layer will increase sufficiently compared with the viscosity ol'the newly applied ink layer so as to implement wet trapping of the newly printed la\er thereby producing a coloristic or visual effect. In practical terms, a water based energy curable ink composition is highly desirable, as its use complies with health and anti-pollution regulations that limit the amount ol'solvents permitted to escape in the environment. I herelbrc the present invention will be described using aqueous ink compositions, inasmuch as such ct)mpositions are the most iikeh to be used. Such limitation in the description of the invention is. howexer. not to be construed as limiting, and radiant energy curable inks oi' similar ink \ iscositx profiles and comparable non-reactive diluent evaporation characteristics are considered within the scope of the present invention. I he method provided by the present invention lor applying multiple, at least panl_\ superposed, ink layers on a substrate, veiics on the rapid and relatively significant change in the viscosity of an energy curable liquid nexographic ink (which ma\ be a water-based ink containing a diluent, such as water), after it has been dep(^sited as a laser onto a substrate. I'he substrate suitable for use in the present imenlion may contain previously applied layers. As for the ink layers applied under the present in\ ention. each ink layer is deposited onto the substrate in an inking station. 1 here are as many inking stations as there are individual inks used in printing the color image. At each inking station, the ink is transferred from an ink reservoir through an anilox roll to a llexographie printing plate, such as a Cyrel® polymer printing plate produced by li.l. Dupont de Nemours and Company. Inc. The ink is then transferred from the printing plate onto a receiving substrate, such as for example a non-absorbent web or sheet of polyethylene film, or any other absorbent or non-absorbent substrate, which may be printed with a llexographie printing plate. 1 he initial viscosity of Hexographic liquid ink deposited onto the substrate is typically under 40(){) eps, and preferably under 1200 cps. although ink \iscosities of 2.000 cps may be used, depending on the particular printing applicatit)n. As discussed earlier, tow viscosity is preferred in order to achieve good ink transfer from the ink reser\oir through the anilox roll to the printing plate surface. Once the ink has been deposited onto the substrate, the non-reactive diluent begins to evaporate, fhe evaporation rate is a functio)i of the non-reactive diluent selected, along with the ambient conditions of temperature, barometric pressure, and relative humidity. I'A'aporalion is also assisted by the rapid increase in surface area of the applied ink or coating layer and the use of increased air circulation ovei' the ink layer applied to the substrate, which may include air which is blown o\cr the substrate, and by the addition of heat, supplied either by heating the forced air stream blown o\er the substrate, or from infrared lamps and the like, teased on the type of printing ink selected, the removal of even a small amount of the non-reactive diluent will result in significant aiul suitable change in the ink vkscosity of the deposited ink layer. By the time the ink layer, arrives at the next inking station, where another ink layer, lypically ofa different color, is deposited on the substrate and t)\er at least portions, if not all. of the previously deposited ink layer, the ink viscosity of the deposited ink layer will have increased sufficiently to wet-trap that ink layer vvitlioul back trapping the newly deposited ink, having a viscosity typically in the same range as that of the earlier deposited ink at the time of its deposition. 1 hcrefore. by selecting energy curable inks containing small amounts of a viscosity controlling non-reactive diluent, such as water, wet trapping of multiple ink layers can be implemented v\itht)ut the need to change ink viscosity by. lor example, heating the ink. chilling the substrate containing the ink layer, between inking stations, or curing the ink between inking stations. According to the present invention, once all ink layers have been applied, a single curing step with a proper energy-curing source is suflicient to fix all applied layers. 1 he present wet trapping process is not limited to the use orcncig\ curable tlexographic liquid inks, but may encompass the use of at least one ink la_\er of non-energ} curable ink. for example, a layer of an energy curable nexograpliic liquid ink ol" the type di.selosed above may be applied and the application of this la>cr to the substrate may be Ibllowed by the application of a layer oi" a non-energy curable liquid llexographic ink, this second layer having a viscosity that is less than the increased viscosity (through the evaporation of all or part of the diluent) of the first layer. Again, because ol the \iscosity differential, wet trapping may be implemented. If this seconti layer is the uppermost ol' last printed layer, all ink layers may be then be cured and dried \ ia coinentional dr\ing means and methods, to simultaneously lix the deposited ink kneis onto the substrate. In yet another embodiment of the present invention, a number of energy curable and traditional ink layers may be inked in superposed fashion and still employ the wet-trapping technique of this invention. For example, as stated above, a first cnergv curable ink. having a first viscosity, may be applied as a llrst laver. A traditional ink layer, having a lower viscosity than the increased viscositv of the tlrsl mk layer. ma\ then be applied over the increased viscosity layer at a subsequent inking station to form a second layer. A third layer may next be applied over the second layer using second energy curable ink having a lower viscosity than the viscosity of the second layer. The viset)sily ol'this layer will again increase as the non-reactive diluent evaporates before reaching the next inking station. At the fourth inking station, a fourth layer may be applied over the third layer using yet another energy curable ink having a lower viscosity than the increased viscosity of the third layer. Drying of the conventional ink layer may be implemented if the conventional ink layer viscosity is so low that energy curable ink with lower viscosity is not available, 1 hus. it is possible to implement the process of the present invention in what may be reicrred to as a "hybrid"" process, whereby only a certain number of ink layers are implemented by viscosity gradient wet-trapping according to this invention, and wherein certain other ink layers are dried or cured prior to the application of additional ink layers, using combinations of inks. Such hvbrid process, however, while possible and within the scope ol" the present invention, is less efficient than a process wherein all applied layers are energy curable flexographie liquid ink lavers. figure 1 shows an apparatus of the present invention. The apparatus 10 shown in this figure is similar to a central impression piess which is a press often used by the llexographic printing industry to print multiple images comprising a plurality of ink layers having at least some superposed inked areas. Because the technology for building such apparatus is well known in the art. only those elements that have been incorporated in this apparatus to transform a standard central impression press into a llexographic printing press capable of carrying out wet trapping when applying superposed liquid ink layers are discussed. As shown in figure 1 the apparatus 10 includes a substrate supjiorting cylindrical drum 12 having an outer peripheral surface 14. Around the drum 12 peripheral surface 14. there are positioned a number of inking stations 18 spaced along the surface. While three such stations are illustrated, such number is for illustration purpose only and ibvvcr or more stations may be placed around the drum without detracting from the scope of this inventit)n. flach of the inking stations comprises an ink reservoir 20, an inking roll 22 and a printing plate holding toll 24. fhe inking roll is. preferably, an anilox roll and is placed so as to receive ink from the ink reservoir and transfer it to a printing plate mounted on the printing roll, fhe printing roll is positioned with respect to the drum 12 so thai it applies an ink layer onto a web 16 carried by Ihe drum 12 at a point of coulacl "A"". ""15". and "C" respectively lor each station illustrated. Inking stations sucli as described here are well known in the art and commonly used in central inipression presses, therefore no further description is given herein except to state that such inking station must be capable ol" handhng ht|uid inks having viscosities well below 4.000 cps. An energy curing station 38 is prelerably also placed along the web 16 path around the drum 12 at a position that is after the last inking station. Such curing stations are also well known in the art and also recjuire no liirther description except to state that in selecting a curing station for use in ciccordance with the present invention, such station must have an energy output olthc type required to cure the liquid inks used in practicing this inxcntion. riie substrate-supporting drum 12 is rotationally driven at a speed of rotation co rpms. using a drive that may comprise belt 36 and pulleys 32 and 34 driven by a motor 30. Such drive permits changing the speed of rotation o, for example, by changing the relative size of the pulleys 32 and 34. or by changing the rotational speed of pulley 32 driven Iw' motor 30. The drive shown is ibr illustration rather than it being limiting, and (ither drives known in the art for altering the speed of rotation oldrum 12 may be used within the scope of this invention, including direct coupling of a \ariable speed motor to the drum, or connection of a driving motor to the drum through a gear box. and so on. In accordance with the present invention, there is further provided to this apparatus a control system generally indicated by a central control 28. local controls 26. and a user interface 40. fhis control system is used to control the apparatus so that a first liquid ink layer applied onto the web 16 at the Inst inking station 18 at point "A" will ha\e its viscosity increase through evaporation of at least some of the non-reactive diluent to a viscosity higher than the viscosity of a second ink to be applied o\cr it at the subsequent inking station 1 8" at point "B" to a viscosity that is suiricient to wet trap the second liquid ink. The control system may achieve this result in any one of a plurality of ways. In the simplest manner, inking stations 18. 18" and 18" arc all llxed in position around drum 12 at certain angular spacing. Oi ^2 etc. 1 he control system in this case adjusts the speed oi' rotation (o of the drum as a function of the time required for the desired viscosity change through evaporation in a layer ct)ated at point "A"", so that the layer coated at point '"A" arrives at point "B" with a \iscosity sufficiently high to wel trap ;thc ink layer applied there over al point ""B". I he required time is a function of the desired viscosil) change, which is a function of the type of liquid ink used in the two inking stations, the thickness of the layer coaled at the first inking station, and the ambient environmental conditions, which affect exaporalion. II can be determined experimentally for dilTcrent inks and applied ink layer thickness. Preferably this data is derived prior to beginning a printing job and is available lo the operator of the apparatus. Ihc data may be stored in an electronic memory (included in block 28). which is part of the control svstem and is indexed to the type of ink u,sed in each inking station and the thickness of the ink layer to be applied at each inking station. Ihus. an operator can readily access ix)tational speed informalittn simply by inputting to the control system. through an interface 40. the type of ink and ink layer thickness to be applied at inking stations 1 8 and 18". When more than two inking stations are used, as is most likely the ease in actual commercial printing, such control system may be programmed to compute an average speed for the drum 12 which will transport the web between stations 18. 18M8"" etc. at the required time for the ink layers to achieve the requisite evaporation necessary to produce the proper viscosity increase to effect wet trapping at all inking stations. fhe control system may also comprise moveable inking s(atit)ns. which can be moved along the web transport path on the drum surface, thereby changing the angular spacing Oi (h etc. between stations. Such change may be done manually or may be pro\'ided automatically using individual position drives 26 on each inking station as part of the control system fhe control system may also include both a variable speed drive and a variable position drive, so that both the spacing of the inking stations and the speed of rotation (o of the drum can be adjustable to satisfy the requirement that the viscosity of each deposited ink layer increases sufficiently through evaporation to a point where such ink layer wet-traps a subsequent ink layer deposited there over. fhe control sy.stem in such arrangement may contain viscosity change data stored in a memory. 1 his data is indexed in a manner thai provides spacing and speed of rotation information to an operator following entry of the ink type and the intended thickness of the applied layer for a printing job. Ihis may he readily achieved using a programmed Central Processing Unit or ""CPU"", an input device such as a keyboard, a memory and a display device, as is well known in the art. In an alternative control system, the CPU may ct)ntrol directly both the rotational speed ol the drum and the positioning mechanism of the ink stations using, for example, the positioning drives 26 associated with the inking stations, based on the input data regarding the inks and kiyer thickness to be used. Optionally, elements 42 that assist the evaporation of the non-reactive diluent may be placed between inking stations. Such elements ma\ be heating elements or air blowing elements or combinations thereof, and do not inckide the usual solvent recovery equipment typical of the prior art inter-stage dryers. Contrarx to the prior art"s required use ol' inter-station drying elements, these elements are contemplated for optional use with this invention and may be employed to facilitate an accelerated evaporation process so as to increase the applied ink layer viscosity as the layer is transported between inking stations. Since such elements, when present require space, consume energy and tend to heat the drum surface it is preferred to run the process without such elemenls. As a result, equipment built in accordance with this invention allow a construction where the diameter of the drum equipped with a certain amount of printing stations can be reduced and the amount of printing stations around a drum ha\ ing a specitlc diameter can be increased. Also, the drum does not require a special drum cooling system, as is typical of central impression cylinder presses of the prior art which it superllciallN resembles. An equipment built in accordance with the present invention would also allow the change of the drum construction material from the typically metal or metal alloy material to for WE CLAIM: 1. A method for applying multiple ink layers onto a substrate comprising the steps off A. applying onto said substrate at least one ink layer of an energy curable liquid ink having a viscosity of less than about 4000 cps and containing a non-reactive diluent, said applied energy curable ink layer having a ilrst viscosity: B. evaporating at least a portion of said non-reactive diluent in the applied energy curable ink layer, thereby increasing the viscosity of the applied energy curable ink layer. C. Applying onto said substrate and said applied energy curable ink layer, at least one layer of a non-energy curable liquid ink having a viscosity of less than about 4000 cps and containing a non-reactive diluents. Subsequent ink layers having a viscosity lower than the increased viscosity of said previously applied energy curable ink layer. ; and 1). fixing both ink layers onto said substrate. 2. 1 he method as claimed in claim 1 wherein said diluent comprises water. 3. the method as claimed in claim f wherein between 5 wt.% and 50 wt.% of said diluent, based on the weight of the diluent, is comprised of water. 4. The method as claimed in claim i wherein step A is per(oi"med in a first inking station and step C is performed in a subsequent inking station, and wlierein said substrate is transported between said Ilrst inking statit)n and said subsequent inking station at a speed sufficient to allow at least a portion of the diluent in said ink layer to evaporate, thereby increasing said ink layer viscosity sufficienlly to permit trapping of said other ink layer applied over said increased viscosity layer. 5. The method as claimed in claim 1 wherein heat is applied to said applied ink layer to assist in removing al least a portion of the diluent al a rate faster than the evaporation rate of the diluent under ambient tempei'alure. pressure and humidity conditions, 6. The method as claimed in claim 1 wherein an air slieam is applied to said printed ink layer to assist in removing some of the diluent at a rale faster than the evapt)ration rate of the diluent under ambient temperature, pressure and humidity conditions. 7. The method as claimed in claim 1 wherein step (' is repealed at lease one more time following step D. applying an additional ink layer over said fixed ink layers and wherein said additional ink layer is also tixed onto said substrate. 8. fhe method as claimed in 1 wherein following step \) there is applied al leasl one more ink layer using energy curable liquid ink having an ink viscosity less than about 4000 cps and comprising a non-reactive diluent comprised of water. 9. I'he method as claimed in claim 1 wherein following step 1). steps A. B. (' and D are repeated at least once.

Documents:

2379-delnp-2004-abstract.pdf

2379-delnp-2004-claims(cancelled).pdf

2379-delnp-2004-claims.pdf

2379-delnp-2004-complete specification (granted).pdf

2379-DELNP-2004-Correspondence-Others-(27-08-2009).pdf

2379-delnp-2004-correspondence-others.pdf

2379-DELNP-2004-Correspondence-PO-(27-08-2009).pdf

2379-delnp-2004-correspondence-po.pdf

2379-delnp-2004-description (complete).pdf

2379-delnp-2004-drawings.pdf

2379-delnp-2004-form-1.pdf

2379-delnp-2004-form-19.pdf

2379-delnp-2004-form-2.pdf

2379-DELNP-2004-FORM-26.pdf

2379-delnp-2004-form-3.pdf

2379-delnp-2004-form-5.pdf

2379-delnp-2004-pct-101.pdf

2379-delnp-2004-pct-210.pdf

2379-delnp-2004-pct-220.pdf

2379-delnp-2004-pct-304.pdf

2379-delnp-2004-pct-408.pdf

2379-delnp-2004-petition-137.pdf