Treatment of release layer

Abstract

A method for treating a hydrophobic release layer of an intermediate transfer member for use in a printing process in which a negatively charged aqueous inkjet ink is jetted onto the surface of this layer. The method comprises contacting the release layer with a chemical agent which is an amine functionalized silicone. Transfer members comprising such a treated release layer and images printed therefrom are also disclosed.

Claims

1. A method for treating a hydrophobic release layer of an intermediate transfer member for use in a printing process in which a negatively charged aqueous inkjet ink including an organic polymeric resin and a colorant is jetted onto said layer, the method comprising contacting the release layer with a chemical agent which is an amine functionalized silicone, the amine functionalized silicone having at least 0.3 wt. % nitrogen per weight of the chemical agent, and an amine number of at least 7 and not more than 300, a molecular weight of at least 500 and not more than 50,000.

2. The method of claim 1, the chemical agent having no more than one hydroxyl or alkoxy group per molecule of the amine functionalized silicone.

3. The method of claim 1, wherein silicon atoms constitute at least 33% by weight of the chemical agent.

4. The method of claim 1, the chemical agent having at least one of (a) at most 1.0 SiH groups, per molecule of the amine functionalized silicone; and (b) at most 1.0 CC groups, per molecule of the amine functionalized silicone.

5. The method of any claim 1, the chemical agent having a kinematic viscosity of at least 10 square millimeters per second (mm.sup.2/s), and of not more than 1,000,000 mm.sup.2/s.

6. The method of claim 1, wherein the positive charge density of the chemical agent is at least 0.1 milliequivalent per gram (meq/g) of the chemical agent.

7. The method of claim 1, wherein the chemical agent is a polymer which comprises one or more positively chargeable nitrogen atoms, each chargeable nitrogen atom being selected from the group of primary, secondary and tertiary amines and quaternary ammonium groups.

8. The method of claim 1, wherein the chemical agent is a liquid at about 23 C.

9. The method of claim 1, wherein the amine functionalized silicone is a compound of formula I: ##STR00012## wherein R is C.sub.1-6 alkyl, the blocks bearing the subscripts x and y may be randomly mixed, the total value of x is from 10 to 5,000, and the total value of y is from 2 to 20.

10. The method of claim 9, wherein one methyl group of at least one dimethyl siloxane repeat subscripted by x is further substituted by a polyether groups comprising (OC.sub.2H.sub.4).sub.a(OC.sub.3H.sub.6).sub.b optionally terminated by a short alkoxyl of 4 carbon atoms or less or an hydroxyl group; a and b being integers.

11. The method of claim 10, wherein the chemical agent is selected from the group consisting of GP-4 (a compound of formula I wherein R(CH.sub.2).sub.3, x=58 and y=4), GP-6 (a compound of formula I wherein R(CH.sub.2).sub.3, x=100 and y=4), GP-581 (a compound of formula I wherein R(CH.sub.2).sub.3, x=118 and y=11), KF-864 (a compound of formula I having an amine number of about 27-30), X-22 3939A (a compound of formula I wherein part of the dimethyl siloxane repeats are further substituted by polyether groups), and mixtures thereof.

12. The method of claim 1, wherein the chemical agent is applied to the release layer as a conditioning liquid, and a surplus of said conditioning liquid is evened on or removed from the surface of the transfer member.

13. The method of claim 1, the method further comprising removing a vehicle or carrier in which the chemical agent is carried, wherein said removing is optionally achieved by evaporation, and wherein the average thickness of the chemical agent on the release layer after evaporation of the vehicle or carrier is not more than 100 nanometers (nm).

14. The method of claim 1, wherein the hydrophobic outer release layer comprises a silane, silyl or silanol-modified or -terminated polydialkylsiloxane silicone polymer, or hybrids of such polymers.

15. The method of claim 1, wherein the amine functionalized silicone is a compound of formula II: ##STR00013## wherein x is from 5 to 5,000, and R and R, which may be the same or different, are each saturated, linear or branched alkyl groups of 1 to 6 carbon atoms.

16. The method of claim 1, wherein the amine functionalized silicone is a compound of formula III: ##STR00014## wherein the blocks bearing the subscripts x and y may be randomly mixed, the total value of x is from 5 to 5,000, the total value of y is from 1 to 20, and R and R, which may be the same or different, are each saturated, linear or branched alkyl groups of 1 to 6 carbon atoms.

17. The method of claim 12, wherein the chemical agent is applied to the release layer so that a thickness of the conditioning liquid on the release layer prior to removal of the bulk of the carrier is less than 100 micrometers (m).

18. The method of claim 1, wherein a temperature of the release layer, when contacted with the chemical agent, is at least 40 C. and not more than 150 C.

19. The method of claim 1, wherein the method further comprises jetting an ink drop to form an ink film on the chemical agent on the release layer, wherein a ratio of charges in the ink film to charges in the chemical agent in a region covered by said ink film is at least at least 10:1.

20. The method of claim 1, wherein the method further comprises jetting an aqueous inkjet ink image on the release layer having the chemical agent thereupon; the aqueous inkjet ink comprising an aqueous solvent, a colorant which is preferably a pigment, and a negatively chargeable polymeric resin; removing the solvent from the jetted aqueous inkjet ink; and transferring the image to a substrate.

Description

DRAWINGS

(1) Some embodiments of the invention will now be described further, by way of examples, and with reference to the accompanying drawings. The description, together with the figures, makes apparent to a person having ordinary skill in the art how some embodiments of the invention may be practiced. The figures are for the purpose of illustrative discussion and no attempt is made to show structural details of a printing system in which the presently claimed invention may be practiced or of any embodiment in more detail than is necessary for a fundamental understanding of the inventions. For the sake of clarity and convenience of presentation, some objects depicted in the figures are not necessarily shown to scale. In the figures:

(2) FIG. 1 is a schematic representation of a printing system in accordance with which an embodiment of the invention may be used;

(3) FIG. 2 is a schematic representation of an alternative printing system in accordance with which an embodiment of the invention may be used;

(4) FIG. 3A shows a print-out of an ink image transferred from an intermediate transfer member treated according an embodiment of the invention, the release layer being prepared by condensation curing;

(5) FIG. 3B shows a print-out of an ink image transferred from an intermediate transfer member having a release layer prepared by condensation curing, the layer not being treated prior to ink jetting;

(6) FIG. 4 shows a print-out of an ink image transferred from an intermediate transfer member treated according to an embodiment of the invention, the release layer being prepared by condensation curing and the transfer being to coated paper;

(7) FIG. 5 shows a print-out of an ink image transferred from an intermediate transfer member treated according to an embodiment of the invention, the release layer being prepared by addition curing and the transfer being to coated paper; and

(8) FIG. 6 shows print-outs of an ink image transferred from an intermediate transfer member treated according to various embodiments of the invention, the release layer being prepared by condensation curing and the transfer being to coated paper.

(9) The remaining Figures are scans of paper onto which ink was transferred from a hydrophobic release layer, illustrating the effects of contacting the release layer with different (or no) chemical agents prior to jetting of the ink onto the release layer.

GENERAL OVERVIEW OF THE PRINTING PROCESS AND SYSTEM

(10) The printing systems schematically illustrated in FIGS. 1 and 2 essentially include three separate and mutually interacting systems, namely a blanket support system 100, an image forming system 300 above the blanket system 100, and a substrate transport system 500 below the blanket system 100. While circulating in a loop, the blanket passes through various stations including a drying station and at least one impression station. Though the below description is provided in the context of the intermediate transfer member being an endless flexible belt, the present invention is equally applicable to printing systems wherein the intermediate transfer member is a drum, the specific designs of the various stations being accordingly adapted.

(11) The blanket system 100 includes an endless belt or blanket 102 that acts as an intermediate transfer member (ITM) and is guided over two or more rollers. Such rollers are illustrated in FIG. 1 as elements 104 and 106, whereas FIG. 2 displays two additional such blanket conveying rollers as 108 and 110. One or more guiding roller is connected to a motor, such that the rotation of the roller is able to displace the blanket in the desired direction, and such cylinder may be referred to as a driving roller. As used herein, the term printing direction means a direction from the image forming station where printing heads apply ink to the release layer towards the location of the impression station, where the ink image is ultimately transferred to the printing substrate. In FIGS. 1 and 2, the printing direction is illustrated as clockwise.

(12) Though not illustrated in the Figures, the blanket can have multiple layers to impart desired properties to the transfer member. Thus in addition to an outer layer receiving the ink image and having suitable release properties, hence also called the release layer, the transfer member may include in its underlying body any one of a reinforcement layer (e.g., a fabric) to provide desired mechanical characteristics (e.g., resistance to stretching), a compressible layer so that the blanket or the drum surface can conform to the printing substrate during transfer, a conformational layer to provide to the surface of the release layer sufficient conformability toward the topography of a substrate surface, and various other layers to achieve any desired friction, thermal and electrical properties or adhesion/connection between any such layers. When the body of the transfer member comprises a compressible layer, the blanket can be looped to form what can be referred to hereinafter as a thick belt. Alternatively, when the body is substantially devoid of a compressible layer, the resulting structure is said to form a thin belt. FIG. 1 illustrates a printing system suitable for use with a thick belt, whereas FIG. 2 illustrates a printing system suitable for a thin belt.

(13) Independently of exact architecture of the printing system, an image made up of droplets of an aqueous ink is applied by image forming system 300 to an upper run of blanket 102 at a location referred herein as the image forming station. In this context, the term run is used to mean a length or segment of the blanket between any two given rollers over which the blanket is guided. The image forming system 300 includes print bars 302 which may each be slidably mounted on a frame positioned at a fixed height above the surface of the blanket 102 and include a strip of print heads with individually controllable print nozzles through which the ink is ejected to form the desired pattern. The image forming system can have any number of bars 302, each of which may contain an ink of a different or of the same color, typically each jetting Cyan (C), Magenta (M), Yellow (Y) or Black (K) inks. It is possible for the print bars to deposit different shades of the same color (e.g., various shades of gray, including black) or customized mix of colors (e.g., brand colors) or for two print bars or more to deposit the same color (e.g., black). Additionally, the print bar can be used for pigmentless liquids (e.g., decorative or protective varnishes) and/or for specialty inks (e.g., achieving visual effect, such as metallic, sparkling, glowing or glittering look, or even scented effect).

(14) Within each print bar, the ink may be constantly recirculated, filtered, degassed and maintained at a desired temperature and pressure, as known to the person skilled in the art without the need for more detailed description. As different print bars 302 are spaced from one another along the length of the blanket, it is of course essential for their operation to be correctly synchronized with the movement of blanket 102. It is important for the blanket 102 to move with constant speed through the image forming station 300, as any hesitation or vibration will affect the registration of the ink droplets of different colors.

(15) If desired, it is possible to provide a blower 304 following each print bar 302 to blow a slow stream of a hot gas, preferably air, over the intermediate transfer member to commence the drying of the ink droplets deposited by the print bar 302. This assists in fixing the droplets deposited by each print bar 302, that is to say resisting their contraction and preventing their movement on the intermediate transfer member, and also in preventing them from merging into droplets deposited subsequently by other print bars 302. Such post jetting treatment of the just deposited ink droplets, need not substantially dry them, but only enable the formation of a skin on their outer surface.

(16) The image forming station illustrated in FIG. 2 comprises optional rollers 132 to assist in guiding the blanket smoothly adjacent each printing bar 302. The rollers 132 need not be precisely aligned with their respective print bars and may be located slightly (e.g., few millimeters) downstream or upstream of the print head jetting location. The frictional forces can maintain the belt taut and substantially parallel to the print bars. The underside of the blanket may therefore have high frictional properties as it is only ever in rolling contact with all the surfaces on which it is guided.

(17) Following deposition of the desired ink image by the image forming system 300 on an upper run of the transfer member, the image is dried by a drying system 400 described below in more details. A lower run of the blanket then selectively interacts at an impression station where the transfer member can be compressed to an impression cylinder to impress the dried image from the blanket onto a printing substrate. FIG. 1 shows two impression stations with two impression cylinders 502 and 504 of the substrate transport system 500 and two respectively aligned pressure or nip rollers 142, 144, which can be raised and lowered from the lower run of the blanket. When an impression cylinder and its corresponding pressure roller are both engaged with the blanket passing there-between, they form an impression station 550. The presence of two impression stations, as shown in FIG. 1, is to permit duplex printing. In this figure, the perfecting of the substrate is implemented by a perfecting cylinder 524 situated in between two transport rollers 522 and 526 which respectively transfer the substrate from the first impression cylinder 502 to the perfecting cylinder 524 and therefrom on its reverse side to the second impression cylinder 504. Though not illustrated, duplex printing can also be achieved with a single impression station using an adapted perfecting system able to refeed to the impression station on the reverse side a substrate already printed on its first side. In the case of a simplex printer, only one impression station would be needed and a perfecting system would be superfluous. Perfecting systems are known in the art of printing and need not be detailed.

(18) FIG. 2 illustrates an alternative printing system suitable for a thin belt looped blanket which is compressed during engagement with the impression cylinder 506 by a pressure roller 146 which to achieve intimate contact between the release layer of the ITM and the substrate comprises the compressible layer substantially absent from the body of the transfer member. The compressible layer of the pressure roller 146 typically has the form of a replaceable compressible blanket 148. Such compressible layer or blanket is releasably clamped or attached onto the outer surface of the pressure cylinder 146 and provides the conformability required to urge the release layer of the blanket 102 into contact with the substrate sheets 501. Rollers 108 and 114 on each side of the impression station, or any other two rollers spanning this station closer to the nip (not shown), ensure that the belt is maintained in a desired orientation as it passes through the nip between the cylinders 146 and 506 of the impression station 550.

(19) In this system, both the impression cylinder 506 and the pressure roller 146 bearing a compressible layer or blanket 148 can have as cross section in the plane of rotation a partly truncated circular shape. In the case of the pressure roller, there is a discontinuity where the ends of the compressible layer are secured to the cylinder on which it is supported. In the case of the impression cylinder, there can also be a discontinuity to accommodate grippers serving to hold the sheets of substrate in position against the impression cylinder. The impression cylinder and pressure roller of impression station 550 rotate in synchronism so that the two discontinuities line up during cycles forming periodically an enlarged gap at which time the blanket can be totally disengaged from any of these cylinders and thus be displaced in suitable directions to achieve any desired alignment or at suitable speed that would locally differ from the speed of the blanket at the image forming station. This can be achieved by providing powered tensioning rollers or dancers 112 and 114 on opposite sides of the nip between the pressure and impression cylinders. Although roller 114 is illustrated in FIG. 2 as being in contact with the inner/underneath side of the blanket, alignment can similarly be achieved if it were positioned facing the release layer. This alternative, as well as additional optional rollers positioned to assist the dancers in their function, are not shown. The speed differential will result in slack building up on one side or the other of the nip between the pressure and impression cylinders and the dancers can act at times when there is an enlarged gap between the pressure and impression cylinders 146 and 506 to advance or retard the phase of the belt, by reducing the slack on one side of the nip and increasing it on the other.

(20) Independently of the number of impression stations, their configuration, the layer structure of the transfer member and the presence or absence of a perfecting mechanism in such printing systems, in operation, ink images, each of which is a mirror image of an image to be impressed on a final substrate, are printed by the image forming system 300 onto an upper run of blanket 102. While being transported by the blanket 102, the ink is heated to dry it by evaporation of most, if not all, of the liquid carrier. The carrier evaporation may start at the image forming station 300 and be pursued and/or completed at a drying station 400 able to substantially dry the ink droplets to form a residue film of ink solids remaining after evaporation of the liquid carrier. The residue film image is considered substantially dry or the image dried if any residual carrier they may contain does not hamper transfer to the printing substrate and does not wet the printing substrate. The dried ink image can be further heated to render tacky the film of ink solids before being transferred to the substrate at an impression station. Such optional pre-transfer heater 410 is shown in FIG. 2.

(21) FIGS. 1 and 2 depict the image being impressed onto individual sheets 501 of a substrate which are conveyed by the substrate transport system 500 from an input stack 516 to an output stack 518 via the impression cylinders 502, 504 or 506. Though not shown in the figures, the substrate may be a continuous web, in which case the input and output stacks are replaced by a supply roller and a delivery roller. The substrate transport system needs to be adapted accordingly, for instance by using guide rollers and dancers taking slacks of web to properly align it with the impression station.

(22) The Drying System

(23) Printing systems wherein the present invention may be practiced can comprise a drying system 400. As noted any drying system able to evaporate the ink carrier out of the ink image deposited at the image forming station 300 to substantially dry it by the time the image enters the impression station is suitable. Such system can be formed from one or more individual drying elements typically disposed above the blanket along its path. The drying element can be radiant heaters (e.g., IR or UV) or convection heaters (e.g., air blowers) or any other mean known to the person of skill in the art. The settings of such a system can be adjusted according to parameters known to professional printers, such factors including for instance the type of the inks and of the transfer member, the ink coverage, the length/area of the transfer member being subject to the drying, the printing speed, the presence/effect of a pre-transfer heater etc.

(24) Operating Temperatures

(25) Each station of such printing systems may be operated at same or different temperatures. The operating temperatures are typically selected to provide the optimal temperature suitable to achieve the purported goal of the specific station, preferably without negatively affecting the process at other steps. Therefore as well as providing heating means along the path of the blanket, it is possible to provide means for cooling it, for example by blowing cold air or applying a cooling liquid onto its surface. In printing systems in which a treatment or conditioning fluid is applied to the surface of the blanket, the treatment station may serve as a cooling station.

(26) The temperature at various stage of the process may also vary depending on the exact composition of the intermediate transfer member, the inks and the conditioning fluid, if needed, being used and may even fluctuate at various locations along a given station. In some embodiments of the invention, the temperature on the outer surface of the transfer member at the image forming station is in a range between 40 C. and 160 C., or between 60 C. and 90 C. In some embodiments of the invention, the temperature at the drying station is in a range between 90 C. and 300 C., or between 150 C. and 250 C., or between 180 C. and 225 C. In some embodiments, the temperature at the impression station is in a range between 80 C. and 220 C., or between 100 C. and 160 C., or of about 120 C., or of about 150 C. If a cooling station is desired to allow the transfer member to enter the image forming station at a temperature that would be compatible to the operative range of such station, the cooling temperature may be in a range between 40 C. and 90 C.

(27) As mentioned, the temperature of the transfer member may be raised by heating means positioned externally to the blanket support system, as illustrated by any of heaters 304, 400 and 410, when present in the printing system. Alternatively and additionally, the transfer member may be heated from within the support system. Such an option is illustrated by heating plates 130 of FIG. 1. Though not shown, any of the guiding rollers conveying the looped blanket may also comprise internal heating elements.

(28) Blanket and Blanket Support System

(29) The intermediate transfer member can be a belt formed of an initially flat elongate blanket strip of which the ends can be releasably fastened or permanently secured to one another to form a continuous loop. A releasable fastening for blanket 102 may be a zip fastener or a hook and loop fastener that lies substantially parallel to the axes of rollers 104 and 106 over which the blanket is guided. A zip fastener, for instance, allow easy installation and replacement of the belt. A permanent securing may be achieved by soldering, welding, adhering, and taping the ends of the blanket to one another (e.g., using Kapton tape, RTV liquid adhesives or PTFE thermoplastic adhesives with a connective strip overlapping both edges of the strip). Independently of the mean elected to releasably or permanently secure these ends to form a continuous flexible belt, the secured ends, which cause a discontinuity in the transfer member, are said to form a seam. The continuous belt may be formed by more than one elongated blanket strip and may therefore include more than one seam.

(30) In order to avoid a sudden change in the tension of the belt as the seam passes over rollers or other parts of the support system, it is desirable to make the seam, as nearly as possible, of the same thickness as the remainder of the blanket. It is desirable to avoid an increase in the thickness or discontinuity of chemical and/or mechanical properties of the belt at the seam. Preferably, no ink image or part thereof is deposited on the seam, but only as close as feasible to such discontinuity on an area of the belt having substantially uniform properties/characteristics. Alternatively, the belt may be seamless.

(31) Blanket Lateral Guidance

(32) In some instances, the blanket support system further includes a continuous track that can engage formations on the side edges of the blanket to maintain the blanket taut in its width ways direction. The formations may be spaced projections, such as the teeth of one half of a zip fastener sewn or otherwise attached to each side edge of the blanket. Such lateral formations need not be regularly spaced. Alternatively, the formations may be a continuous flexible bead of greater thickness than the blanket. The lateral formations may be directly attached to the edges of the blanket or through an intermediate strip that can optionally provide suitable elasticity to engage the formations in their respective guiding track, while maintaining the blanket flat in particular at the image forming station. The lateral track guide channel may have any cross-section suitable to receive and retain the blanket lateral formations and maintain it taut. To reduce friction, the guide channel may have rolling bearing elements to retain the projections or the beads within the channel.

(33) The lateral formations may be made of any material able to sustain the operating conditions of the printing system, including the rapid motion of the blanket. Suitable materials can resist elevated temperatures in the range of about 50 C. to 250 C. Advantageously, such materials are also friction resistant and do not yield debris of size and/or amount that would negatively affect the movement of the belt during its operative lifespan. For example, the lateral projections can be made of polyamide reinforced with molybdenum disulfide.

(34) As the lateral guide channels ensure accurate placement of the ink droplets on the blanket, their presence is particularly advantageous at the image forming station 300. In other areas, such as within the drying station 400 and an impression station 550, lateral guide channels may be desirable but less important. In regions where the blanket has slack, no guide channels are present. Further details on exemplary blanket lateral formations or seams that may be suitable for intermediate transfer members according to the present invention are disclosed in PCT Publication No. WO 2013/136220.

(35) Such lateral formations and corresponding guide channels are typically not necessary when the intermediate transfer member is mounted on a rigid support.

(36) The ends of the blanket strip are advantageously shaped to facilitate guiding of the belt through the lateral channels and over the rollers during installation. Initial guiding of the belt into position may be done for instance by securing the leading edge of the belt strip introduced first in between the lateral channels to a cable which can be manually or automatically moved to install the belt. For example, one or both lateral ends of the belt leading edge can be releasably attached to a cable residing within each channel. Advancing the cable(s) advances the belt along the channel path. Alternatively or additionally, the edge of the belt in the area ultimately forming the seam when both edges are secured one to the other can have lower flexibility than in the areas other than the seam. This local rigidity may ease the insertion of the lateral formations of the belt strip into their respective channels.

(37) The blanket support system may comprise various additional optional subsystems, such as a Cleaning Station, a Cooling Station and a Conditioning Station, the latter to be detailed separately in the following section.

(38) Blanket Cleaning Station

(39) Though not shown in the figures, the blanket system may further comprise a cleaning station which may be used to gently remove any residual ink images or any other trace particle from the release layer. Such cleaning step may for instance be applied in between printing jobs to periodically refresh the belt. The cleaning station may comprise one or more devices each individually configured to remove same or different types of undesired residues from the surface of the release layer. In one embodiment, the cleaning station may comprise a device configured to apply a cleaning fluid to the surface of the transfer member, for example a roller having cleaning liquid on its circumference, which preferably should be replaceable (e.g., a pad or piece of paper). Residual particles may optionally be further removed by an absorbent roller or by one or more scraper blades.

(40) The Control Systems

(41) The above descriptions are simplified and provided only for the purpose of enabling an understanding of exemplary printing systems and processes with which the presently claimed invention may be used. In order for the image to be properly formed on the blanket and transferred to the final substrate and for the alignment of the front and back images in duplex printing to be achieved, a number of different elements of the system must be properly synchronized. In order to position the images on the blanket properly, the position and speed of the blanket must be both known and controlled. For this purpose, the blanket can be marked at or near its edge with one or more markings spaced in the direction of motion of the blanket. One or more sensors can be located in the printing system along the path of the blanket to sense the timing of these markings as they pass the sensor. Signals from the sensor(s) can be sent to a controller which may also receive an indication of the speed of rotation and angular position of any of the rollers conveying the blanket, for example from encoders on the axis of one or both of the impression rollers. The sensor(s) may also determine the time at which the seam of the blanket passes the sensor. For maximum utility of the usable length of the blanket, it is desirable that the images on the blanket start as close to the seam as feasible. For a successful printing system, the control of the various stations of the printing system is important but need not be considered in detail in the present context. Exemplary control systems that may be suitable for printing systems in which the present invention can be practiced are disclosed in PCT Publication No. WO 2013/132424.

(42) Blanket Conditioning Station

(43) In some printing systems, the intermediate transfer member can be treated to further increase the interaction of the compatible ink with the ITM, or further facilitate the release of the dried ink image to the substrate, or provide for a desired printing effect. The treating station may apply a physical treatment or a chemical treatment. In the present case the ITM is treated with a chemical conditioning agent, such as an emulsion of a positively charged polymer according to the teachings herein. The compositions being applied to the intermediate transfer member are often referred to as treatment solutions or conditioning fluids and the station at which such treatment may take place is referred to as a conditioning station. This station is typically located upstream the image forming station and the treatment is applied before an ink image is jetted.

(44) Such a station is schematically illustrated in FIG. 1 as roller 190 positioned on the external side of the blanket adjacent to roller 106 and in FIG. 2 as applicator 192. Such a roller 190 or applicator 192 may be used to apply a thin even film of treatment solution containing a conditioning chemical agent. The conditioning fluid can alternatively be sprayed onto the surface of the blanket and optionally spread more evenly, for example by the application of a jet from an air knife. Alternatively, the conditioning solution may be applied by passing the blanket over a thin film of conditioning solution seeping through a cloth having no direct contact with the surface of the release layer. Surplus of treatment solution, if any, can be removed by air knife, scrapper, squeegee rollers or any suitable manner. As the film of conditioning solution being applied is typically very thin, its vehicle is totally removed from the film by the time it reaches the print bars of the image forming system and the blanket surface is substantially dry upon entry through the image forming station. Preferably, the very thin dried layer of chemical agent on the surface of the blanket assists the ink droplets to retain their film-like shape after they have impacted the surface of the blanket.

(45) The conditioning solution is applied with every cycle of the belt. Alternatively, it may be applied periodically at intervals of suitable number of cycles.

(46) The purpose of the applied chemical agent is to counteract the effect of the surface tension of the aqueous ink upon contact with the hydrophobic release layer of the blanket, without necessarily reducing said surface tension. Without wishing to be bound by theory, it is believed that such pre-treatment chemical agents, for instance some positively charged polymers, will adhere (temporarily at least), to the silicone surface of the transfer member to form a positively charged layer. However, the amount of charge that is present in such a layer is believed to be much smaller than the negative charge in the droplet itself. The present inventors have found that a very thin layer of chemical agent, perhaps even a layer of molecular thickness, is adequate. This layer of pre-treatment chemical agent on the transfer member may be applied in very dilute form of the suitable chemical agents. Ultimately this thin layer may be transferred onto the substrate, along with the image being impressed.

(47) When the ink droplet impinges on the transfer member, the momentum in the droplet causes it to spread into a relatively flat volume. In the prior art, this flattening of the droplet is almost immediately counteracted by the combination of surface tension of the droplet and the hydrophobic nature of the surface of the transfer member.

(48) In embodiments of the invention, the shape of the ink droplet is frozen such that at least some and preferably a major part of the flattening and horizontal extension of the droplet present on impact is preserved. It should be understood that since the recovery of the droplet shape after impact is very fast, the methods of the prior art would not effect phase change by agglomeration and/or coagulation and/or migration.

(49) Without wishing to be bound by theory, it is believed that, on impact, the positive charges which have been placed on the transfer member attract the negatively charged polymer resin particles of the ink droplet that are immediately adjacent to the surface of the member. It is believed that, as the droplet spreads, this effect takes place along a sufficient area of the interface between the spread droplet and the transfer member to retard or prevent the beading of the droplet, at least on the time scale of the printing process, which is generally on the order of seconds.

(50) As the amount of charge is too small to attract more than a small number of charged resin particles in the ink, it is believed that the concentration and distribution of the charged resin particles in the drop is not substantially changed as a result of contact with the chemical agent on the release layer. Furthermore, since the ink is aqueous, the effects of the positive charge are very local, especially in the very short time span needed for freezing the shape of the droplets.

(51) While the applicants have found that coating the intermediate transfer member with a polymer utilizing a roller or an application cloth is an effective method for freezing the droplets, it is believed that spraying or otherwise chemically transferring positive charge to the intermediate transfer member is also possible.

(52) Ink

(53) Inks that are suitable for use in conjunction with the treated are release layer are, for example, aqueous inkjet inks that contain (i) a solvent comprising water and optionally a co-solvent, (ii) a negatively chargeable polymeric resin (the ink may include a small amount of a pH-raising substance to ensure that the polymer is negatively charged), and (iii) at least one colorant. In some embodiments, one or more of the following is also true of the inks: water constitutes at least 8 wt. % of the ink; the at least one colorant is dispersed or at least partly dissolved within the solvent and constitutes at least 1 wt. % of the ink; the polymeric resin is dispersed or at least partially dissolved within the solvent and constitutes 6 to 40 wt. % of the ink; the average molecular weight of the polymeric resin is least 8,000; and prior to jetting the ink has at least one of (i) a viscosity of 2 to 25 centipoise at at least one temperature in the range of 20-60 C. and (ii) a surface tension of not more than 50 milliNewton/m at at least one temperature in the range of 20-60 C. In some embodiments, the ink is such that, when substantially dried, (a) at at least one temperature in the range of 90 C. to 195 C., the dried ink has a first dynamic viscosity in the range of 1,000,000 (110.sup.6) cP to 300,000,000 (310.sup.8) cP, and (b) at at least one temperature in the range of 50 C. to 85 C., the dried ink has a second dynamic viscosity of at least 80,000,000 (810.sup.7) cP, wherein the second dynamic viscosity exceeds the first dynamic viscosity; and/or the weight ratio of the resin to the colorant is at least 1:1. In some embodiments, the ink is such that, when substantially dried, the dried ink has: (i) a first dynamic viscosity within a range of 10.sup.6 cP to 5.Math.10.sup.7 cP at at least a first temperature within a first 15 range of 60 C. to 87.5 C.; and (ii) a second dynamic viscosity of at least 6.Math.10.sup.7 cP, for at least a second temperature within a second range of 50 C. to 55 C. The colorant may contain a pigment, preferably a nanopigment, for example having an average particle size (D.sub.50) of not more than 120 nm. With respect to the ink, substantially dried refers to ink that has no more solvent and other volatile compounds than does a layer of the ink of 1 mm initial thickness after such a layer is dried in an oven for 12 hours at 100 C.

(54) Ink Image Heating

(55) The heaters, either inserted into the support plates 130 or positioned above the blanket as intermediate drying system 224 and drying station 214, are used to heat the blanket to a temperature that is appropriate for the rapid evaporation of the ink carrier and compatible with the composition of the blanket. For blankets comprising for instance silanol-, modified or terminated polydialkylsiloxane silicones in the release layer, heating may vary within a range from 50 C. to 220 C., depending on various factors such as the composition of the inks and/or of the conditioning liquid(s) if needed. The blanket temperature may be substantially the same from ink deposition to transfer (e.g., of the order of 150 C.) or may vary between the various stations of the printing system. When using beneath heating of the transfer member, it is desirable for the blanket to have relatively high thermal capacity and low thermal conductivity, so that the temperature of the body of the blanket 102 will not change significantly as it moves between the pre-treatment or conditioning station, the image forming station and the impression station(s). When using top heating of the transfer member, the blanket would preferably include a thermally insulating layer to prevent undue dissipation of the applied heat. To apply heat at different rates to the ink image carried by the transfer surface, independently of the architecture of a particular printing system, additional external heaters or energy sources (not shown) may be used to apply energy locally, for example prior to reaching the impression stations to render the ink residue tacky (see 231 in FIG. 3), prior to the image forming station to dry the conditioning agent if necessary and at the printing station to start evaporating the carrier from the ink droplets as soon as possible after they impact the surface of the blanket.

(56) The external heaters may be, for example, hot gas or air blowers 306 (as represented schematically in FIG. 1) or radiant heaters focusing, for example, infrared radiation onto the surface of the blanket, which may attain temperatures in excess of 175 C., 190 C., 200 C., 210 C., or even 220 C.

(57) The residue film left behind in embodiments of the invention may have an average thickness below 1500 nm, below 1200 nm, below 1000 nm, below 800 nm, below 600 nm, below 500 nm, below 400 nm, or below 300 nm.

(58) As explained above, temperature control is of paramount importance to the printing system if printed images of high quality are to be achieved. This is considerably simplified in the embodiment of FIG. 3 in that the thermal capacity of the belt is much lower than that of the blanket 102 in the embodiments of FIGS. 1 and 2.

(59) It has also been proposed above in relation to the embodiment using a thick blanket 102 to include additional layers affecting the thermal capacity of the blanket in view of the blanket being heated from beneath. The separation of the belt 210 from the blanket 219 in the embodiment of FIG. 3 allows the temperature of the ink droplets to be dried and heated to the softening temperature of the resin using much less energy in the drying section 214. Furthermore, the belt may cool down before it returns to the image forming station which reduces or avoids problems caused by trying to spray ink droplets on a hot surface running very close to the inkjet nozzles. Alternatively and additionally, a cooling station may be added to the printing system to reduce the temperature of the belt to a desired value before the belt enters the image forming station. Cooling may be effected by passing the belt 210 over a roller of which the lower half is immersed in a coolant, which may be water or a cleaning/treatment solution, by spraying a coolant onto the belt of by passing the belt 210 over a coolant fountain.

(60) In some of the arrangements discussed hitherto, the release layer of the belt 210 has hydrophobic properties to ensure that the tacky ink residue image peels away from it cleanly in the transfer station. However, at the image forming station the same hydrophobic properties are undesirable because aqueous ink droplets can move around on a hydrophobic surface and, instead of flattening on impact to form droplets having a diameter that increases with the mass of ink in each droplet, the ink tends to ball up into spherical globules. As discussed, in structures using a hydrophobic release layer, steps therefore need to be taken to encourage the ink droplets, which flatten out into a disc on impact, to retain their flattened shape during the drying and transfer stages.

(61) Printing systems as described herein may be produced by modification to existing lithographic printing presses. The ability to adapt existing equipment, while retaining much of the hardware already present, considerably reduces the investment required to convert from technology in common current use. In particular, in the case of the embodiment of FIG. 1, the modification of a tower would involve replacement of the plate cylinder by a set of print bars and replacement of the blanket cylinder by an image transfer drum having a hydrophobic outer surface or carrying a suitable blanket. In the case of the embodiment of FIG. 3, the plate cylinder would be replaced by a set of print bars and a belt passing between the existing plate and blanket cylinders. The substrate handling system would require little modification, if any. Color printing presses are usually formed of several towers and it is possible to convert all or only some of the towers to digital printing towers. Various configurations are possible offering different advantages. For example each of two consecutive towers may be configured as a multicolor digital printer to allow duplex printing if a perfecting cylinder is disposed between them. Alternatively, multiple print bars of the same color may be provided on one tower to allow an increased speed of the entire press.

(62) The following examples illustrate embodiments of the invention.

Example 1

(63) An inkjet ink formulation was prepared containing:

(64) TABLE-US-00001 Ingredient Function wt. % Carbon Black, Monarch Pigment 1.5 700 (Cabot) Joncryl 2038, 43.5% Resin 13.8 emulsion in water (6% solids) Tween 40 Softening agent 3.0 Capstone FS-65 (DuPont) Non-ionic fluorosurfactant 0.01 Water Balance to 100% Joncryl HPD 296 (35.5% Dispersant 4.2 water solution) (BASF) (solid resin) Ethylene glycol (Aldrich) Water-miscible co-solvent 15

(65) Preparation procedure: A pigment concentrate, containing pigment (14%), water (79%) and Joncryl HPD 296 (7%) were mixed and milled using a homemade milling machine. The progress of milling was controlled by particle size measurement (Malvern, Nanosizer). The milling stopped when the particle size (D.sub.50) reached 70 nm. Then the rest of the materials were added to the pigment concentrate. After mixing the ink was filtered through 0.5 micrometer filter.

(66) The efficacy of various materials in improving the transfer of the black ink formulation described above were tested as follows:

(67) Emulsions containing 1, 2 and 3 wt. % of GP-4 (amine functional silicone of formula I, with the blocks randomly distributed, x=58, y=4, RC.sub.3H.sub.6, amine number=90, MW 4922) in water were prepared by mixing an appropriate amount of GP-4 in an appropriate amount of distilled water at room temperature for five minutes at 3000 rpm in an IKA high shear mixer. These were respectively referred to as SOL1, SOL2 and SOL3. A fourth emulsion, called SOL4, was prepared from 100 parts distilled water, two parts GP-965 (amine functional silicone of formula II, RRC.sub.3H.sub.6, x=10, amine number=200, MW 1000) and 0.04 parts Triton X-100 (non-ionic surfactant) by ultrasonic mixing (Vibra mixer from Sonics, 20 kHz, 750 W). For the sake of comparison, an aqueous solution containing 0.3 wt. % polyethylene imine (Lupasol PS, charge density 20 meq/g, MW 750,000, hereinafter referred to as the PEI solution; see PCT publication No. WO 2013/132339 for more details) was prepared.

(68) ##STR00011##

(69) A silanol-terminated polydimethyl siloxane silicone (PDMS) release layer was prepared by condensation curing of the following ingredients: Gelest DMS-S27 (silanol terminated polydimethylsiloxane of formula IV above, having an average MW of 18,000 and about 0.2% OH), 100 parts, Colcoat Ethyl silicate 48, 9 parts Tib Kat 223 (Dioctyltin dineodecanoate catalyst), 0.5 parts, as described in PCT publication No. WO 2013/132432, which is incorporated herein by reference. The release layer was applied in dust-free, environmentally controlled conditions of temperature at 20-25 C. and relative humidity between 40% and 70% to a standard blanket body that provides an underlying mechanical support. The thickness of the condensation cured release layer (CCRL) was approximately 40-80 m. A piece of this printing blanket of approximately 200 mm300 mm area having the release layer on its outer surface was fixed on a hotplate and heated to 70-80 C. SOL1 (comprising about 1 wt. % GP-4) and the PEI solution were applied to separate halves of the release layer to a thickness of approximately 1 micrometer to completely cover the image transfer surface of the release layer. Specifically, the solution was sprayed at the image transfer surface of the release layer and then evened to the desired thickness using a wipe. After about 30 seconds, the water of the pretreatment solution evaporated, leaving a sub-micron thin layer of PEI or aminosilicone fluid as a chemical agent coating the image transfer surface of the release layer. A thin film of the black ink described above was spread on the treated release layer using a smooth rod. The ink did not show any beading on the release layer surface. After about 30 s the ink was dried on the release layer and a piece of Condat 135 gsm coated paper was pressed against the inked release layer. The process was repeated using uncoated paper (Xerox Business ECF/003R91820 Photocopier Paper DIN A4 80 gsm). In all four cases (amine functionalized silicone and PEI, coated and uncoated paper) the ink was completely transferred to the paper, giving a continuous shiny film on the paper.

(70) This method of assessing the suitability of a conditioning agent to satisfactorily treat the surface of a release layer such that ink applied thereafter is fully transferred therefrom is also termed the drawdown screening method. It was used for preliminary selection of conditioning agents tested first in undiluted form (neat, namely at 100% concentration) as provided by their respective suppliers. The agents that promoted full transfer of a continuous ink film to coated and uncoated papers included GP-4, GP-6, GP-316, GP-345, GP-965 (from Genesee), KF-861, KF-864, KF-869 (from Shin Etsu), Silamine A0-EDA, and Silamine D2-EDA (from Siltech). The amine number of these materials, as provided by supplier or determined experimentally, was respectively 90, 50, 54, 7, and 200, for the polymers of the GP series; 127, 27-30, and 54 for the polymers of the KF series; and 230 and 250 for the polymers of the Silamine series.

(71) Other candidates yielded only partly satisfactory results (e.g., partially prevented beading on the tested release layer, but enabled full transfer of the resulting discontinuous dry ink film). Such compounds, like Rhodorsil H21 645 of Bluestar Silicones, may be less suitable because of the nature of their amine group which being hindered might be underexposed within the molecule thus less able to interact either with the release layer or the ink or both. Alternatively, or additionally such compounds might be less suitable in view of their low nitrogen content (e.g., 0.25% N in Rhodorsil H21 645), as its Amine Number of 18 favorably compare to GP-345.

Example 2

(72) Example 1 was repeated, but this time the surface of the CCRL PDMS release layer, instead of being spread with a thin film of ink, was printed with drops of ink of 9 picoliter drop size, using a Fujifilm Dimatix DMP-2800 printer (www.fujifilmusa.com/products/industrial_inkjet_printheads/deposition-products/dmp-2800/index.html). Again, beading of the ink on the treated release layer surface was not observed, and results similar to those in Example 1 were obtained for both the PEI and amine functionalized silicone (SOL1 comprising about 1 wt. % of GP-4) treatments, for both coated and uncoated paper as above-identified.

Example 3

(73) Example 1 was repeated, but this time SOL4 (comprising about 2 wt. % GP-965) was used to treat the CCRL PDMS release layer instead of SOL1. A continuous shiny film was obtained on the coated paper for both the PEI and amine functionalized silicone treatments. Beading of the ink on the treated release layer surface was not observed. Printing on the uncoated paper showed that transfer from the PEI-coated portion of the release layer was not complete, but transfer from the GP-965-coated portion was complete.

Example 4

(74) Example 1 was repeated, except that instead of SOL1, the CCR PDMS release layer was coated with SOL5 (100 parts distilled water, 4 parts GP-4, 0.02 parts Triton X-100, sonicated as in the preparation of SOL4), and the Fujifilm Dimatix printer was used to jet 9 pL drops of the ink. Beading of the ink on the treated release layer surface was not observed. The dried ink film was transferred to both coated and uncoated paper as described in Example 1. Print quality following treatment with SOL5 (comprising about 4 wt. % of GP-4) was compared to PEI by optical density and dot size measurements. Such evaluations were generally made on at least three representative areas of a typical print-out or on representative areas of at least three print-outs. Optical density (OD) was measured using a Spectrodensitometer (500 Series from X-rite) at the desired ink coverage, a higher OD indicating a better transfer. The average diameters of the printed dots was measured by microscopy using optical & laser microscopes (LEXT from Olympus) at 20 magnification. Generally isolated dots were selected from areas with ink coverage of 10% or less.

(75) FIG. 3A shows a typical print-out of a 100% ink coverage test file on coated paper. For comparison, FIG. 3B displays an illustrative print that may be obtained under the same conditions when the release layer is not treated with a conditioning fluid before the jetting of the ink. FIG. 4 shows a typical print out on coated paper of a different test file, the printed pattern including a scale of different ink coverages ranging from 2% to 100% and the profile of a human face as complex image. As can be seen in the Figs. and in the table below, the print quality obtained on Condat 135 gsm coated paper using SOL5 was at least equivalent if not better than that obtained using PEI. The average dot size for at least 6 dots taken from two print-outs as represented in FIG. 4 was 41 micrometers for ink printed from the PEI-treated release layer and 42.2 m for the amine functionalized silicone treated release layer. A larger diameter suggests retention of the spreading of the ink droplet on the release layer and good transfer therefrom.

(76) Similar results were obtained when replacing SOL5 comprising GP-4 by SOL6 comprising GP-316, to be further detailed in Example 7. Interestingly, the so-treated release layer (i.e. GP-316 on CCRL PDMS) was able to satisfactorily transfer the ink image to paper up to about a hundred prints without having to reapply conditioning liquid in between the prints. The results are summarized in the following table:

(77) TABLE-US-00002 Degree of coverage OD - PEI OD - GP-4 (SOL5) 100%, uncoated paper* 1.40 1.49 100%, coated paper** 2.25 2.26 80%, coated paper 1.26 1.36 30%, coated paper 0.46 0.47 *Xerox Business ECF/003R91820 Photocopier Paper DIN A4 80 gsm **Condat 135 gsm

Example 5

(78) The size of the droplets, and the zeta potentials, of the SOL2 and SOL5 emulsions were determined using a Zeta sizer. For SOL2, which had a white, milky appearance, D50 was 3.2 micrometers, and the zeta potential was 30 mV. For SOL5, the corresponding values were 1.1 micrometers and 22 mV, respectively. It will be appreciated that the zeta potentials were positive, indicating the presence of positive charges.

Example 6

(79) The experiment of Example 1 was repeated, but this time the release layer was prepared by addition curing the following components, the part per weight of every ingredient indicated in parentheses for each of the five ACRL compositions:

(80) TABLE-US-00003 ACRL-1 ACRL-2 Component Component Description (Parts) (Parts) Vinyl polymer Gelest DMS-V35 Gelest DMS-V35 (100) (70) Hanse XP RV-5000 (30) Vinyl Resin Gelest VQM 146 Gelest VQM 146 (40) (40) Inhibitor Evonik Inhibitor Evonik Inhibitor 600 (3) 600 (3) Platinum Gelest SIP6831.2 Gelest SIP6831.2 Catalyst (0.1) (0.1) Hydride Gelest HMS-301 Gelest HMS-301 crosslinker (5) (12) ACRL-3 ACRL-4 ACRL-5 Component Component Component Description (Parts) (Parts) (Parts) Vinyl polymer Gelest DMS-V46 Gelest DMS-V35 Gelest DMS-V35 (100) (100) (100) Vinyl Resin Gelest VQM 146 Gelest VQM 146 Gelest VQM 146 (40) (40) (40) Inhibitor Evonik Inhibitor Evonik Inhibitor 600 (5) 600 (3) Platinum Gelest SIP6831.2 Gelest SIP6831.2 Gelest SIP6831.2 Catalyst (0.1) (0.1) (0.1) Hydride Gelest HMS-301 Gelest HMS-301 Gelest HMS-301 crosslinker (16) (5) (5) Functional Momentive Momentive Lubrizol HP-A89- Additive SR-545 (8) SR-545 (8) B1 (5)

(81) All the ingredients were hand mixed, degassed for five minutes under vacuum (25-40 mmHg), then spread on a substrate (e.g., a blanket body) in a dust-free environment under environmentally controlled conditions of temperature (20-25 C.) and of relative humidity (40-70 RH %). Once uniformly applied on the substrate, the specimens were cured. Generally, the thickness of the addition cured release layer of all so prepared ACRL specimen was between about 40 m and about 80 m. The first release layer composition described in above table was cured for one hour at 140 C. to yield addition cured release layer ACRL-1. ACRL-2 to ACRL-5 were cured at temperatures of 100-130 C. for about 15 minutes.

(82) The treatment of ACRL-1, ACRL-2, ACRL-4 and ACRL-5 with the amino silicone fluid (SOL1) facilitated good spreading of the ink on the treated release layer and complete transfer to both types of paper. A typical print-out on coated paper, as transferred for instance from the ACRL-1 treated release layer, is shown in FIG. 5. The treatment with PEI resulted in a discontinuous ink film on the uncoated paper, indicating poor transfer.

(83) As mentioned, SOL1 was prepared by diluting 1:100 in distilled water, an amino silicone of formula I, namely GP-4. Similar experiments were performed with solutions comprising a 1:100 water dilution of X-22 3939A; GP-965; GP-316; and Silamine D2018 EDA; corresponding respectively to amino silicones of formula I partly substituted with polyether groups; formula II; formula III and formula III partly substituted with polyether groups. These 1% diluted amino silicone fluids were tested on blankets comprising ACRL-1, ACRL-2, ACRL-4 and ACRL-5 release layers, except for the diluted solution of Silamine D2018 EDA, which was tested on an ACRL-3 surface and found likewise appropriate for suitable spreading of the ink on the release layer and complete transfer to the printing substrates. The diluted solution of X-22 3939A was additionally tested on an ACRL-3 surface and found suitable for proper transfer to the printing substrates.

Example 7

(84) An emulsion of GP-316 (an amine silicone polymer of formula III, in which RC.sub.3H.sub.6, RC.sub.2H.sub.4, x=400 and y=8, amine number 54, MW 31,000) (SOL-6) was prepared as follows: 100 parts distilled water, 4 parts GP-316, 0.02 parts Triton X-100 (a surfactant) were mixed by ultrasonic mixing (Vibra mixer from Sonics, 20 kHz, 750 W). The Fujifilm Dimatix printer was used to print 9 pL drops of the afore-described black ink on an addition-cured release layer coated blanket prepared as described in example 6. Print quality was compared by optical density and dot size measurements following transfer to the above-identified coated and uncoated papers. The print quality obtained using SOL6 (comprising about 4 wt. % of GP-316) on the ACRL-1 release layer was compared to print quality obtained using PEI on the condensation cured release layer (CCRL). The average dot size for at least 6 dots taken from two print-outs was 41 micrometers for ink printed from the PEI-treated condensation-cured release layer and 43 m for the amine functionalized silicone-treated addition-cured release layer. The print-outs obtained from blankets treated with GP-316 were highly similar to the ones obtained from blankets treated with GP-4, see FIG. 5, but for conciseness are not shown. As can be seen in the table below, the print quality obtained using SOL6 for the treatment of a printing blanket having an ACRL-1 outer surface was at least equivalent if not better than that obtained using a printing blanket having a CCRL outer surface conditioned with PEI. SOL6 was not compared to PEI on ACRL-1 blanket, as the reference failed to provide a satisfactory printing baseline. The amino silicones conditioning agents may therefore advantageously be compatible with a broad range of printing blankets.

(85) TABLE-US-00004 OD - PEI OD - GP-316 Degree of coverage on CCRL (SOL6) on ACRL-1 100%, uncoated paper 1.40 1.45 100%, coated paper 2.25 2.20 80%, coated paper 1.26 1.34 30%, coated paper 0.46 0.54 * Xerox Business ECF/003R91820 Photocopier Paper DIN A4 80 gsm ** Condat 135 gsm

(86) When the print-outs of the complex profile pattern were compared, the images obtained from SOL6 treated ACRL-1 blanket were qualitatively better than the images obtained from the PEI CCRL blanket (data not shown). Interestingly, the so treated release layer was able to satisfactorily transfer the ink image to paper up to about a hundred prints without having to reapply conditioning liquid in between the prints. Without wishing to be bound by theory, it is surmised that this may be due to partial penetration of the chemical agent into the release layer.

Example 8

(87) The surface energy of the cured and optionally treated release layers described above was measured using Surface Energy Test Liquids (Dyne level testing following ISO 8296) from Dyne TECHNOLOGY. This form of measurement is based on the ISO method for measuring the surface energy of a polyethylene film. When the Dyne level test liquid is applied to the surface, the liquid will either form a continuous film on the surface or bead into small droplets. If the Dyne test fluid remains as a film for 3 seconds, the substrate will have a minimum surface energy of that fluid value, expressed in milliNewtons/meter (mN/m). Should the Dyne test fluid reticulate or bead into droplets in less than 1 second then the surface energy of the substrate is lower than that of the fluid itself. The exact surface energy (Dyne level) can be determined by applying a range of increasing or decreasing values of Dyne test fluids. The range of test liquids available starts from 23 dyn/cm until 70 dyn/cm (i.e. 23-70 mN/m). The tests were performed at room temperature; the results are shown in the table below:

(88) TABLE-US-00005 Surface Energy Surface (dyn/cm) ISO8296 Condensation Cured Release Layer (CCRL; Ex. 1) <23 CCRL + SOL1 <23 CCRL + SOL2 <23 CCRL + SOL3 <23 CCRL + SOL4 <23 CCRL + SOL5 <23 CCRL + SOL6 <23 Addition Cured Release Layer (ACRL; Ex. 6) <23 ACRL-1 + SOL6 <23

(89) These results confirm that the amino functional silicone treatment fluids do not measurably increase the surface energy of the release layer.

Example 9

(90) The advancing contact angles of a rolling drop (2 l) of distilled water on the cured and optionally treated release layers above-described, was measured using a Kruss apparatus (camera measurement). For each tested surface, three repeat measurements were performed at room temperature (23 C.) and the average is presented in the following Table:

(91) TABLE-US-00006 Advancing Surface Angle () Condensation Cured Release Layer (CCRL; Ex. 1) 105 CCRL + SOL5 107 CCRL + SOL6 103 Addition Cured Release Layer (ACRL-1; Ex. 6) 106 ACRL-1 + SOL5 105 ACRL-1 + SOL6 108

(92) This test confirms that the amino functional treatment fluid does not affect the contact angle of a water drop on the release layer in a significant manner.

Example 10

(93) Formulations of different amino silicone materials were made in order to study the relationships between the structure, the amine number, the conditioning effect and the print quality obtained on Coated paper (Condat Gloss 135 gsm). 2 parts of respectively GP-4, GP-6, GP-316, GP-345, GP-965 (all of Genesee Polymer Corporation), and KF864 (Shin Etsu) were emulsified in 100 parts of distilled water using an ultrasonic mixer (Vibra mixer from Sonics, 20 kHz, 750 W). These amino silicone conditioning fluids were compared to a PEI water solution as reference. Each tested conditioning agent was applied to a blanket having a condensation cured PDMS release layer as described in Example 1.

(94) An inkjet ink formulation was prepared containing:

(95) TABLE-US-00007 Ingredient Function wt. % Heliogen Cyan S 7320 (BASF) Pigment 1.5 Joncryl 2038 (43.5% Resin 13.8 emulsion in water) (6% solids) (BASF) Joncryl HPD 296 Dispersant 4.2 (35.5% water solution) (solid resin) (BASF) Tween 40 Softening agent 3.0 BYK 349 Non-ionic silicone 1.0 surfactant Ethylene glycol (Aldrich) Water-miscible co- 15.0 solvent Water Carrier Balance to 100%

(96) Preparation procedure: A pigment concentrate, containing pigment (14%), water (79%) and Joncryl HPD 296 (7%) were mixed and milled using a homemade milling machine. The progress of milling was controlled by particle size measurement (Malvern, Nanosizer). The milling stopped when the particle size (D.sub.50) reached 70 nm. Then the rest of the materials were added to the pigment concentrate. After mixing the ink was filtered through 0.5 micrometer filter to yield the jettable blue ink used thereafter.

(97) The Fujifilm Dimatix printer was used to jet 9 pL drops of this blue ink upon the treated release layer of the printing blanket. Following the drying of the ink for 30 seconds, a piece of coated paper (Condat Gloss 135 gsm) was pressed against the dried inked image and peeled away from the blanket. The print outs so prepared, at least ten per each conditioning fluid, were analyzed as previously described for size of isolated dots and optical density at various ink coverages (100%, 80% and 30%). An untreated blanket was used as control and the dots obtained therefrom were too far from circular shapes to be measured, the entry being therefore marked as Not Relevant (NR). The results presented in the below table are averages of at least 10 dots diameters (in micrometers) and of at least 3 measurements of optical density. The amino silicone materials are listed by increasing amine number from left to right.

(98) TABLE-US-00008 Untreated Control PEI GP 345 KF 864 Chemical NR NR III I Formula Amine NR 1800- 7 27 Number 2000 Dot size NR 28.5 19.9 17.9 OD 100% 0.238 1.68 1.42 1.34 OD 80% 0.248 1.15 0.437 0.321 OD 30% 0.271 0.491 0.389 0.239 Untreated Control GP 6 GP 316 GP 4 GP 965 Chemical NR I III I II Formula Amine NR 50 54 90 200 Number Dot size NR 28.1 28.9 28.7 26.6 OD 100% 0.238 1.77 1.72 1.75 1.76 OD 80% 0.248 0.958 1.17 1.07 0.801 OD 30% 0.271 0.414 0.457 0.436 0.321

(99) From the above table, it is clear that the treatment of the release layer with any of the amino silicones being tested, as well as with the reference PEI solution, significantly improves the quality of the print outs yielding measurable round dots and optical densities up to above six-fold higher than untreated control. Moreover, it seems that for the release layer being used and for the ink being jetted in the present example, the print quality as indicated by dot size measurements improves with increasing amine number till a plateau of dot diameter is reached. This observation is further supported by the optical density read on the print outs at the different ink coverages. Amine silicones of all chemical formulae gave satisfactory results, primary amines, pendant on chain, of formula I, primary and secondary amine, pendant on chain, of formula III and terminated primary amines of formula II.

(100) FIG. 6 shows scans of representative print-outs obtained using the afore-mentioned conditioning fluids and reference agent. It should be noted that as the experiments were performed under the same conditions (e.g., same batch of ink) and preferably on the same day, certain experimental defects (e.g., strike out line resulting from defective print head nozzle) can be ignored for the sake of comparison. Though the OD values retrieved from the ink coverage scale can provide a preliminary indication of the suitability of a candidate agent to serve for treatment of the printing blanket, the print-out of a more complex image, in the present case the profile picture displayed at the bottom of the printed sample, can further help distinguish between the tested materials. For instance, though the OD values measured for the printouts obtained from blankets treated with PEI reference or GP-4, GP-6 and GP-316 look highly similar, the profile image obtained with the amino silicones conditioning agents seems better than the PEI baseline. Understandingly this method herein described to compare different materials can similarly be used to compare different concentrations of a same material, or any other desired parameter. It will be appreciated that such method allows optimizing the formulation of a conditioning fluid suitable for any type of release layer or ink, as exemplified with the blankets having the disclosed CCRL and ACRL release layer being used to transfer aqueous inkjet inks.

(101) The contents of all of the above mentioned applications of the Applicant, as well as other publications mentioned herein, are incorporated by reference as if fully set forth herein.

(102) The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons skilled in the art to which the invention pertains.

(103) In the description and claims of the present disclosure, each of the verbs, comprise include and have, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb. As used herein, the singular form a, an and the include plural references unless the context clearly dictates otherwise. For example, the term an impression station or at least one impression station may include a plurality of impression stations.

(104) As used herein, when a numerical value is preceded by the term about, the term about is intended to indicate +/10%.

(105) Citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the invention.

(106) Section headings are used herein to ease understanding of the specification and should not be construed as necessarily limiting.

(107) Certain marks referenced herein may be common law or registered trademarks of third parties. Use of these marks is by way of example and shall not be construed as descriptive or limit the scope of this invention to material associated only with such marks.