GB2518149A - Apparatus for treating an intermediate transfer member of a printing system - Google Patents

Abstract

An apparatus for treating the surface of an intermediate transfer member (ITM) (102, Fig.2) of an indirect printing system. The apparatus comprises a frame (146, Fig.5) mounted beneath a section of the ITM, a liquid permeable or perforated cloth 148 stretched over the frame, and a jetting assembly (142, Fig.5) mounted beneath the cloth to direct one or more jets of a treatment solution onto the underside of the cloth to deflect the cloth upwards towards the surface of the ITM (102, Fig.2). The treatment solution that passes through the cloth forms a liquid film that prevents the cloth from contacting the surface of the ITM (102, Fig.2).The apparatus may included a heating/cooling device for modifying the temperature of the treatment solution or the ITM (102, Fig.2). The apparatus may also include a squeegee roller (144, Fig.3) or an air knife for removing surplus treatment solution from the surface of the ITM (102, Fig.2). For silicone based ITM surfaces the treatment solution may be polyethylenimine (PEI).

Description

APPARATUS FOR TREATING AN INTERMEDIATE TRANSFER MEMBER OF

A PRINTING SYSTEM

FIELD OF THE INVENTION

The present invention relates to an indirect printing system in which liquid ink droplets are deposited at an image forming station onto a movable intermediate transfer member (ITM), dried while being transported by the ITM and transferred at an impression station from the ITM onto a substrate. Specifically this disclosure pertains to an apparatus for treating the surface of such transfer members prior to the deposition of an ink image.

BACKGROUND

Digital printing techniques have been developed that allow a printer to receive instructions directly from a computer without the need to prepare printing plates. Amongst such printing devices are colour laser printers, which use dry toners and the xerographic process, and the widely used inkjet printers, which use liquid inks and rely on inkjet or bubble jet processes. Such printing devices typically directly apply the desired image to the final printing substrate (e.g., paper). In general, the resolution of such processes is limited.

For instance, liquid inks may wick into fibrous substrates requiring the use of substrates specially coated to absorb the liquid ink in a controlled fashion or to prevent its penetration below the surface of the substrate. Such coated substrates may not address all issues associated with direct printing and may even create their own problems. For instance, if the surface of the substrate remains wet following the application of the ink, and such an event is not obviated by the use of all coated substrates, additional costly and time consuming steps are needed to dry the ink, so that it is not later smeared as the substrate is being handled, for example stacked or wound into a roll. Furthermore, excessive wetting of the substrate causes cockling and makes double sided printing (also termed perfecting or duplex printing) difficult, if not impossible.

In commercial settings, there exist other printing systems, some relying on indirect or offset printing techniques. In such processes, an intermediate image of the fmal desired pattern (e.g., a mirror image) is typically formed on an ITM and later transferred from the ITM to the final printing substrate. The ITM may be constructed either as the cylindrical surface of a rigid drum or as an endless flexible belt guided over rollers. The intermediate image can be, as in HP-Indigo printers, an electrostatic image produced on an electrically charged image bearing cylinder by exposure of compatible oil-based inks to laser light, the ink image being then transferred by way of a blanket cylinder onto paper or any other substrate. Though such systems are better suited for high quality digital printing the use of oil-based inks has raised environmental concerns.

The present Applicant has recently disclosed a printing system and process wherein inks having an aqueous carrier are jetted onto an ITM which transports them to an impression station where they are transferred to the desired substrate. Such systems allow the distance between the surface (also called the release layer) of the ITM and the inkjet print head to be maintained constant and reduces wetting of the substrate, as the inks may 13 be dried while being transported by the ITM before they are applied to the substrate.

Consequently, the final image quality on the substrate is less affected by the physical properties of the substrate and benefits from various other advantages as a result of the image remaining above the substrate surface. More details on such systems arc disclosed in International Patent Application No. PCT/1B20 13/051716, filed on March 5, 2013.

In the printing system of the latter patent application, the surface of the ITM is selected to be hydrophobic in order to facilitate the transfer of the ink droplets, after they have been dried and become tacky, from the TTM onto the substrate. The fact that the surface is hydrophobic gives rise to a need to transiently fix the aqueous ink droplets to avoid them beading up into globules and moving on the ITM.

23 For some silicone-based release surfaces, one way of fixing the ink droplets on the hydrophobic release surface calls for the application of a treatment solution to the release surface of the ITM. Such solution may be water-based and comprise a conditioning agent such as polyethylenimine (PEI).

The present invention seeks to provide an apparatus for effectively treating the surface of the ITM of an indirect printing system with a liquid treatment solution after it has passed through the (or the last) impression station and before it returns to the image forming station in order to assist in fixing of ink droplets.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an apparatus for treating a surface of an intermediate transfer member of an indirect printing system, the apparatus comprising a frame to be mounted beneath a section of the intermediate transfer member, a liquid permeable or perforated cloth stretched over the frame, and a jetting assembly mounted beneath the cloth to direct one or more jets of a treatment solution onto the underside of the cloth to deflect the cloth upwards towards the surface of the intermediate transfcr member, thc trcatment solution passing through thc cloth to form a liquid film that prevents the cloth from contacting the surface of the intermediate transfer member.

Suitable typcs of cloth may includc natural or synthetic, woven or non-woven, fabrics, that may bc porous or optionally gently perforated at a suitable mesh. The cloth preferably satisfies one or more of being mechanically stable under the operating pressure, rcsistant to thc flow rate, dimension stable during its lifetime, mesh stable, chemically inert and resistant toward the treatment solution to be applied, thermally resistant to the operating temperature. The type of cloth may further depend on the flow rate of the pump and its ability to deflect the cloth toward the surface of the ITM. Two parameters can be considered, the diameter of the holes in the cloth through which the treatment solution would pass and the percent open area, that is to say the fraction of the total surface area of the cloth occupied by the holes, expressed as a percentage. In some embodiments, the diameter of the cloth holes is between 20 and 150 micrometer (jim), or about 50 jim, or about 70 jim, or about 90 jim, or about 110 am. In further embodiments, the percent of open area in the cloth is between 10 and 50%, or about 25%, or about 35%, or about 45% It will be appreciated that the two parameters can counterbalance one another and a cloth having a low percent open area with relatively large holes can act in a manner similar to a cloth having a higher percent open area with relatively smaller holes, as far as the area to be treated on the ITM is concerned. Such variations may affect the jetting flow rate needed to deflect the cloth, a parameter readily adjustable.

The fibres can be natural and organic (e.g., cotton), metal-based, glass-based, ceramic-based and synthetic (e.g., plastic polymers). Each fibre may comprise a monofilament of the afore-mentioned materials or multi-filaments. In one embodiment, the cloth is woven. In woven fabrics, the diameter of the fibres forming the warp and weft of the fabric correlate with the dimensions of the holes in between such fibres, through which the treatment solution can pass. The warp and weft fibres can be of the same material and/or have similar physical properties, but alternatively can have different characteristics, as long as the fabric can provide for the desired cloth attributes. In a further embodiment, the cloth is made of thermoplastic polymers (e.g., aramide. high density or ultra high density polyethylene, polyesters, etc.), optionally resistant to heat of up to 150°C. In an additional embodiment, the distance between the yarns are further stabilized (e.g., ironing of woyen thermoplastic fabrics) to reduce or prevent the movement of the fibres one relatively to the other.

The frame may conveniently be mounted within or above a trough for collecting surplus treatment solution.

A pump may suitably be provided to draw the treatment solution from the trough and supply it to the jetting assembly.

In order to achieve uniform flow and pressure across the width of the ITM being treated, the jetting assembly in some embodiments of the invention may comprise a plurality of jets transversely spaced apart from one another and mounted on a manifold 13 configured to ensure equal pressure at each of the individual jets.

In another embodiment of the invention, the jetting assembly may comprise a surface with a plurality of holes transversely spaced apart from one another. The holes may have any geometrical shape suitable for the jetting of a treatment solution and they can be circles, ovals, squares, or any other polygon.

In some embodiments of the invention, the shortest distance between the centre of any two jets or two holes is no less than 4 millimetres (mm), or no less than 6 mm, or no less than 8 mm, or no less than 10 mm, or no less than 12 mm. The shortest distance between any two jets may be no more than 8 mm, or no more than 10 mm, or no more than 12 mm, or no morc than 15 mm, or no more than 20 mm. The shortest distance between 23 any two jets may lie between 4 mm and 20 mm, or between 6mm and 15 mm, or between 6mm and 12mm, or between 6mm and 10mm, or between 8 mm and 10mm.

Thc diametcr of a hole in thc jetting assembly may bc no morc than 1.5 mm, or no more than 2.5 mm, or no more than 5 mm. The diameter of a hole in the jetting assembly may be no less than 1 mm, or no less than 2 mm, or no less than 3 mm. The diameter of a hole in the jetting assembly may lie between 1 mm and 5 mm, or between 2 mm and 5 mm, or between 1 mm and 2.5 mm.

In order to achieve an extended interaction surface between the surface of the ITM and the treating agent in the liquid film of treatment solution overlying the cloth, it is convenient for the jetting assembly to have a two dimensional array of jets opening into a 33 plenum chamber within the manifold.

As the surface of the ITM is delicate and pivotal for the lifespan of the ITM, any apparatus applying treatment solution by directly contacting the surface of the ITM (e.g., with an application roller or a wiping cloth) would cause wcar to thc surface. In thc prcscnt invention, however, the cloth does not contact the surface of the ITM despite being forcibly urged towards it by the jetting assembly. This is because the liquid escaping through the cloth acts in the same manner as the lubrication film of a fluid bearing to maintain thc cloth and thc surface of thc ITM apart. Thcrcforc a liquid film at prcssurc is maintained in contact with the surface of the ITM to coat the entire surface of the ITM with thc trcatmcnt solution aftcr it has passcd through thc last imprcssion station.

The height of the cloth is regulated in such a way that the distance between the cloth and the ITM is sufficiently small to ensure contact between the liquid and the JIM yet sufficicntly large to cnsurc that thcrc will not bc inadvcrtcnt contact bctwccn thc cloth and thc TTM. In practicc, thc trcatmcnt solution may bc jcttcd with sufficient forcc to dcflcct thc cloth towards thc ITM so that thc distancc bctwccn thc cloth and thc JIM is no morc than 1 mm, or no more than 2 mm, or no more than 3 mm, or no more than 4 mm, or no more than 5 mm, and no less than 1 mm, or no less than 2 mm, or no less than 3 mm, or no lcss than 4 mm, and convcnicntly lying within thc range 1 mm and 5 mm, or bctwccn I mm and 4 mm, or between 1 mm and 3 mm, or between 2 mm and 5 mm, or between 2 mm and 4 mm. The treatment solution seeps through the cloth and fills the gap between the 23 TTM and the cloth.

The apparatus of the invention ensures comprehensive coverage of the surface of the ITM with the desired conditioning agent, because the ITM remains in constant contact with a liquid laycr ovcr a largc arca that cxtcnds ovcr thc cntirc cloth. This providcs morc even, thorough and comprehensive coverage than directly jetting the surface of the ITM.

Advantageously, the increased coverage efficiency achievable by the apparatus of the invention allows thc conccntration of conditioning agcnt comprised in thc trcating solution to be reduced, as compared with the concentration that would be needed using a smaller area of treatment (e.g., using an application roller) or a less uniform application methods (e.g., sprinklers or bare fountains). The use of lower amounts of conditioning agent, in 33 addition to bcing morc cost effectivc, may bc beneficial to thc printing proccss. Unifomily applied treating solutions arc cxpcctcd to rcducc variations in thc trcatmcnt of differcnt areas of the JTM, which in turn decreases possible disparities in the ink image, therefore improving print quality. The treatment solution is furthermore confined to flow smoothly

S

in the small gap between the cloth and the surface of the ITM, thereby avoiding any spray, splatter and aerosol formation that would result from aiming jets of the treatment solution directly onto thc rcleasc surfacc of the ITM.

Furthermore, the relatively large area of contact between the above-cloth film of treatmcnt solution and the ITM may servc as a mcans to modif' thc tcmpcraturc of thc ITM, typically to cool it. Such cooling cffcct might be achicved by the mcrc diffcrcncc in temperatures of the ITM and of the treatment solution tinder any set of operating conditions. Alternatively, the treatment solution may be actively cooled (or heated) so that the difference in temperature between the ITM and the solution being jetted by the apparatus of the present invention is at least 10°C, or at least 20°C, or at least 30°C, or at least 40°C, or at least 50°C.

Even though a treatment solution is being applied to the surface of the ITM, the latter surface (e.g., the release layer) can be required to arrive dry at the image forming station.

For this reason, in some embodiments, the apparatus may include a pair of squeegee rollers, and/or an air knife for removing surplus treatment solution from the surface of the ITM. Squeegee rollers are preferred to a doctor blade as they are in rolling contact rather than sliding contact with the ITM and therefore do not subject the surface to wear.

To maintain the desired pressure within the liquid film between the cloth and the surface of the ITM, embodiments of the invention may include backing rollers on the opposite side of the ITM from the cloth to prevent movement of the ITM away from the cloth.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic representation of a printing system within which the apparatus of the invention is deployed; Figure 2 is an isometric projection from above and one side of an apparatus of the invention for applying a treatment solution to the ITM of the printing system in Figure 1; Figure 3 is an isometric projection of part of the apparatus in Figure 2 from the top and the opposite side; Figure 4 is an isometric projection showing only the jetting assembly and the squeegee roller of the apparatus in Figures 2 and 3; Figure 5 is plan view of the jetting assembly from above; and Figurc 6 is a scction through thc jctting assembly of Figure 5 takcn along thc line VI-

VL

DETAILED DESCRIPTION OF THE DRAWINGS

Though thc invention can bc uscd to apply any typc of treatment solution to thc outcr surface of an ITM, it will be described below with reference to examples where the release layer has liquid repelling properties toward the inks of the printing system in which the 13 present apparatus can be deployed. The following examples may refer in particular to the treatment of hydrophobic surfaccs to rcducc or prcvcnt thcir repelling effect toward liquid inks having an aqueous carrier typically comprising a colouring agent (e.g., piguents or dyes) and a polymeric resin, but the invention need not be limited to such particular embodiments.

In Figure 1, there is shown schematically a printing system 100 having an intcrmcdiatc transfer mcmbcr in thc form of a blankct 102 having a treatable outcr surfacc (e.g., a hydrophobic release layer repelling aqueous inks) guided over various rollers of a blanket conveyor system 103 to travel repeatedly in an endless loop through various stations. Thc invcntion is equally applicable to printing systems wherein the intermediate 23 transfer member is a drum, the specific designs of the various stations being accordingly adapted.

At an image forming station 104, print bars 106 deposit droplets of inks onto the outer surface of the blanket 102 to form an ink image. The inks of the different bars 106 are usually of different colours and all the inks have particles of resin and colouring agent in an aqueous carrier, apart from some transparent inks or varnishes which may not contain a pigment.

Though the image forming station illustrated in Figure 1 comprises eight print bars, an image forming station may comprise fewer or more print bars. For instance, an image forming system may have only three print bars jetting ryan (C), Magenta (M) or Yellow 33 (Y) inks, respectively, or four print bars, with the additional bar applying Black ink (K).

The blanket 102 then passes through a drying station 108 where the ink droplets are dried and rendered tacky before they reach impression stations 110 where the ink droplets are transferred onto sheets 112 of substrate. Each impression station 119 includes an impression cylinder 110a and a pressure roller ilOb which have between them a nip within which the blanket 102 is pressed against a substrate. In the illustrated embodiment, the subsnte is formed as sheets 112 that are transferred from an input stack 114 to an output stack 116 by a substrate transport system 118. The substrate transport system 118, which is generally conventional and need not therefore be described in detail in the present context, may comprise a perfecting system to allow double-sided, or duplex, printing. Two impression stations 110 are provided to enable printing on both sides of the substrate, one impression station being positioned upstream and the other downstream of the perfecting system. Alternatively, the printing systems in which the present invention may be used can have a single impression station and different perfecting means, if any.

It should be mentioned that the invention is equally applicable to printing systems designed to print on a substrate in the form of a continuous web instead of individual sheets. In such cases, the substrate transfer system is accordingly adapted to convey the substrate from an input roller to a delivery roller.

After passing through the impression stations 110, the blanket 192 in Figure 1 passes through a conditioning station 120 before returning to the image forming station 104.

Persons skilled in the art to which this invention pertains will readily appreciate that such printing systems may include additional stations, not represented in the Figures for the sake of clarity. For instance, such systems may have a selectively engageable blanket cleaning station or cooling station or heating station or substrate coating station.

The present invention is primarily coneemed with the station 120, the purpose of which is to apply a treatment solution containing a conditioning agent to the surface of the blanket 192. In addition, the station may serve to modi' the temperature of the surface of the blanket so that the temperature of this surface before the first print bar of the image forming station is within a desired range. For some blankets having a silicone based outer surface, the conditioning agent may be PET. The outer surface of the transfer member 102 can be made hydrophobic to assist in a clean transfer of the tacky ink image to the substrate at the impression station(s) 110 and the function of the conditioning agent is to assist in fixing the ink droplets to the outer surface of the blanket 102. The present invention can be used for various treatment solutions independently of the nature of the treating agents (herein called conditioning agents) they may comprise and of the purpose they may fulfil in the printing systems being considered. Moreover, though the fluid being applied by thc apparatus herein discloscd is referrcd to as a "treatmcnt solution", this terminology needs not be limited to mean that the conditioning agents are homogeneously dissolved in the solvent of relevance. Suspensions, dispersions and emulsions are equally applicable using the apparatus and method according to the present teachings.

Parameters that may need to be adjusted to optimise an apparatus according to the present teachings include, but are not limited to, any of the dimensions and mesh opening of the cloth sufficient for the treatment purpose, the type of the cloth compatible with the treating agent and permeable to the treatment solution, the jetting rate sufficient for the solution being considered and the cloth being used, the temperature of the solution which may be modified as compared to ambient conditions if desired, and the extcnt of removal of excess trcatmcnt solution, if at all. Such adjustmcnts can be readily accomplished and

arc encompassed in the prcscnt disclosure.

The apparatus constituting the station 120 will now be described with reference to Figures 2 to 6 of the drawings. Thc apparatus 120 comprises a support structure 122, a trough 124 and a support bar 126. The support structure 122, which is shown in Figure 2 but not in Figure 3, can be mounted either on the substrate transport system 118 or on the blanket convcyor system 103. The trough 124 is adjustably conncctcd to the structure 122 and configured to lie belleath the blanket 102 (shown as bethg semi-transparent th Figure 2). The support bar 126 is also connected to the mounting frame of either the blanket conveyor system 103 or the substrate transport system 118, but lies above the blanket and extends transversely to thc direction of movement of the blanket 102.

The support bar 126 has two rearward (referenced to the direction of blanket movement) projecting brackets 127 that support two rollers 128 and 130 and two forward projecting brackets 129 that support a further roller 132. The purpose of all three rollers 128, 130 and 132 is to limit upwards movement of the blanket and to confine it to travel in a plane at a predetermined distance above the components that reside within the trough 124.

33 In another embodiment of the invention, the blanket 102 can be stretched with sufficient tension over the rollers of the blanket conveyor system so that the blanket does not dcflcct upwards or sag downwards. In this embodiment, thc support bar 126, projccting brackets 127 and 129, and the three rollers 128, 130 and 132, may be removed from the apparatus.

The trough 124 has upright sides 124a and an optionally sloping base 124b so that it may contain the treatment solution to be applied to the surface of the blanket 102. Two parallel crossbeams 140 extend between opposite sides 124a of the trough 124, and these are shown more clearly in Figure 4.

[he crossbeams support a jotting assembly 142 and a squeegee roller 144. the jetting assembly 142, which will be described in more detail below by reference to Figure 5 and Figure 6, creates a fountain of the treatment solution that, on the other side of the cloth, fonms a film through which the surface of the blanket 102 passes. After having been uniformly wetted by the jetting assembly 142, the blanket is then squeezed between the squeegee roller 144 and the backing roller 132, to remove all the surplus treatment solution from the surface of the blanket 102 which then can arrive substantially dry at the image forming station 104. As an altemative to the squeegee roller 144, it is possible to use an air knife to remove surplus treatment solution from the surface of the blanket 102. For other treatment application purposes, it may bc desired for surplus of treatment solution not to be removed, in which case the squeegee roller is disengaged or may be omitted from the apparatus.

Without wishing to be bound by theory, it is believed that when using such apparatus in squeegeeing mode a layer of only atomic thickness of the treatment solution is left adhering to the surface of the blanket. This layer when comprising the conditioning agent PET illustrating the present invention is believed to modify the distribution of electric charge on the surface of the blanket sufficiently to cause an electrostatic interaction between the surface of the blanket and the ink droplets to fix the droplets when they are deposited onto the surface of the blanket at the image forming station 104.

The jetting assembly 142 is surrounded by a frame 146 over which a cloth 148 (shown only in Figure 6) is stretched. In the illustrated embodiment, the frame 146 is formed of two L-shaped brackets 146a and 146b that are clamped to one another and to the jetting assembly 142 by clamping bolts 146c. Alternatively, the frame may be formed of one or more sections. As seen in Figure 6, the sides of the frame 146 are of U-shaped section and the upper limb of the U-shape serves as a means for anchoring the cloth 148.

Altcrnativcly, thc frame may be formcd of a variety of different cross-section profiles, e.g., C-shape, L-shape, etc. The cloth may for example be wrapped around reinforcement rods that are in turn screwed to frame 146 or retained against it by spring clips.

The jetting assembly 142 is formed of an upper plate 150 into which holes 152 act as jets. The underside of the plate 1O is machined to define plenum chamber 14 that communicates with all the holes 152. A second plate 156 that is screwed to the underside of the plate 150 seals the plenum chamber 154 and provides a connector 158 for enabling the pressure side of a pump to be connected to the interior of the manifold formed by the two plates 150 and 156. As can be seen in the plan view of Figure 5, the holes 152 are arranged in a rectangular anay so that cloth 148 is deflected upwards towards the release surface of the blanket 102 by a uniform anay of jets operating at equal pressures as they are all connected to the same plenum chamber 154. Ahhough the holes are depicted in a rectangular array in Figure 5, this is not the only suitable array. Any array capable of providing substantially uniform pressure to the cloth is acceptable.

In operation, the trough 124 is filled with the treatment solution. A pump which is not shown but mounted in the support structure 122 draws the treatment solution from the trough 124 and supplies it undcr pressure to the plenum chambcr 154 of the jetting assembly 142. Alternatively, the pump may draw the treatment solution from a reservoir not shown on the present illustration of the printing system 100. The solution passes out of the jet holes 152 under pressure and impinges on the underside of the cloth 148 which then Slates upwards to a position where, in the absence of any liquid flow through it, it would contact the release surface of the blanket. The cloth is however porous or perforated so that the treatment solution passing through the cloth forms a lubrication film between the cloth and the blanket that prevents the two from contacting one another, acting in the same way as oil in a friction bearing or air in an air bearing. In this way, the surface of the blanket is exposed to a pressurised liquid film to treat its surface but is not subjected to abrasion.

In another embodiment of the invention, not presently shown in the illustrations, the pump draws treatment solution from a reservoir. The surplus solution, which has already engaged the blanket, is gathered in the trough. This surplus solution is then removed to a container (e.g., a waste container). The removal proccss may bc either automatic, for example by means of using a pump, or manually, by means of removing the trough when the surplus solution has reached a critical level (e.g., when the solution height is close to the height of the sidewall of the trough).

In another embodiment of the invention, the pressure of the treatment solution is such that, even in the absence of a blanket, the cloth would not be deflected sufficiently to intrude into the plane of the blanket and the small distance between the cloth and the blanket is filled by the treatment solution.

The surplus treatment solution can then be removed, if desired, by means of the squeegee roller 144 before it returns to the image forming station 104.

The treatment solution pump would in time be depleted and a level detection system may be provided to maintain the amount of solution in the trough/reservoir at a desired level.

13 While persons skilled in the art to which the invention pertains will readily understand that the teachings herein can be used to apply any treatment solution, for any purpose, to an intermediate transfer member of a printing system, examples of ink formulations or transfer members that may benefit from the present invention in connection with certain treatment solutions are provided below.

Non-limiting examples of ink compositions for which the present invention can be suitable are water based inks as disclosed in co-pending International Patent Application No. PCT/1B2013/051755, filed on March 5,2013.

Intermediate transfer members that may be used in connection with such water based inks, though a priori repelling them, may comprise a silicone material. Under suitable 23 conditions, a silanol-, sylyl-or silane-modified or terminated polydialkylsiloxane silicone material has been found to work well. However the exact formulation of the silicone is not critical as long as the selected material allows for release of the image from the transfer member to a final substrate. Further details of non-limiting examples of release layers and intermediate transfer members for which the present invention can be suitable are disclosed in co-pending PCT Application No. PCT/1B2013/05 1743, filed on March 5,2013.

As previously explained, the release layer may be pre-treated with a conditioning agent that may partly reduce the hydrophobic effect of some of the afore-mentioned silicone-based release layers. Further details on conditioning solutions suitable for printing processes wherein water-based inks are jetted onto hydrophobic surface of transfer 33 members and which may be used in printing systems for which the present invention can be suitable are disclosed in co-pending PCT Application No. PCT/1B2013/000757, filed on March 5,2013.

The contents of all of the above mentioned applications of the Applicant are incorporated by reference as if fully set forth herein.

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 thc vcrb arc not nccessarily a complete listing of mcmbcrs, componcnts, clcmcnts or parts of thc subjcct or subjccts of the verb. As used hcrein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, thc term "an impression station" may include more than one such station.

Claims (21)

1. CLAIMS1. An apparatus for treating a surfacc of an intermediate transfer member of an indirect printing system, the apparatus comprising a frame to be mounted beneath a section of the intemiediate transfer member, a liquid peniieable or perforated cloth stretched over the frame, and a jetting assembly mounted beneath the cloth to direct one or more jets of a treatment solution onto the underside of the cloth to deflect the cloth upwards towards the surface of the intermediate transfer member, the treatment solution passing through the cloth to form a liquid film that prevents the cloth from contacting the surface of the intermediate transfer member.
2. 2. An apparatus as claimed in claim 1, wherein the frame is mounted within or above a trough for collecting surplus treatment solution.
3. 3. An apparatus as claimed in claim 2, wherein a recirculation pump is provided to draw treatment solution from the trough and supply the treatment solution to the jetting assembly.
4. 4. An apparatus as claimed in claim 3, wherein the recirculation pump is selectively capable of drawing the treatment solution from a reservoir or the trough.
5. 5. An apparatus as claimed in any of claims 1 to 4, wherein the jetting assembly comprises a plurality of jets transversely spaced apart from one another and mounted on a manifold configured to ensure equal pressure at each of the individual jets.
6. 6. An apparatus as claimed in claim 5, wherein the jetting assembly has a two dimensional array ofjets opening into a plenum chamber within the manifold.
7. 7. An apparatus as claimed in any of claims 1 to 4, wherein the jetting assembly comprises a surface with a plurality of holes transversely spaced apart from one another.
8. 8. An apparatus as claimed in any of claims 5 to 7, wherein the shortest distance between the centre of any two jets or two holes is no less than 4 millimetres (mm), or no less than 6 mm, or no less than 8 mm, or no less than 10 mm, or no less than 12 mm.
9. 9. An apparatus as claimed in any of claims 5 to 8, wherein the shortest distance between any two jots is no more than 8 mm, or no more than 10 mm, or no more than 12 mm, or no more than 15 mm, or no more than 20 mm.
10. 10. An apparatus as claimed in any of claims 5 to 9, wherein the shortest distance between any two jets is between 4 mm and 20 mm, or between 6 mm and 15 mm, or betwcen 6mm and 12 mm, or between 6mm and 10 mm, or between 8 mm and 10 mm.
11. 11. An apparatus as claimed in any of claims 5 to 10, wherein the diameter of the holes in the jetting assembly is no more than 1.5 mm, or no more than 2.5 mm, or no more than 5 12. An apparatus as claimed in any of claims 5 to 11, wherein thc diamctcr of thc holes in the jetting assembly is no less than 1 mm, or no less than 2 mm, or no less than 3 mm.13. An apparatus as claimed in any of claims 5 to 12, wherein thc diamctcr of thc holes 13 in thc jetting assembly is between 1 mm and 5 mm, or bctwccn 2 mm and 5 mm, or between 1 mm and 2.5 mm.14. An apparatus as claimed in any preceding claim, further including at lcast onc of (i) a pair of squeegee rollers, and (ii) an air knife for removing surplus treatment solution from the surface of the intermediate transfer member.15. An apparatus as claimed in any preceding claim, further comprising backing rollers on thc opposite side of thc intermediate transfer member from thc cloth to prevent movement of the intermediate transfer member away from the cloth.16 An apparatus as claimed in any preceding claim, further comprising a cooling! heating device for modi'ing the temperature of the treatment solution.17. An apparatus as claimed in any preceding claim, wherein the cloth is formed with holes having a diameter between 20 and 150 micrometer (tm).18. An apparatus as claimed in any preceding claim, wherein the cloth is formed with holcs having a diameter of approximately 50 jim, 70 tm, 90 tm, or 110 tm.19. An apparatus as claimed in any preceding claim, wherein the percent open area of the cloth is between 10 and 50%, or approximately 25%, 35%, or 45%.20. An apparatus as claimed in any preceding claim, wherein the cloth is formed of monofilament or multifilament fibres that are selected from any one or more of natural and organic fibres, metal-based fibres, glass-based fibres, ceramic-based fibres, thermoplastic polymer fibres and synthetic fibres.21. An apparatus as claimed in claim 20, wherein the cloth is made of thermoplastic polymers comprising at least one polymer selected from the group comprising aramide, high density polyethylene, ultra high density polyethylene and polyesters.22. Au apparatus as claimed in claim 20 or 21, wherein the fibres are resistant to heat ofupto 150°C.23. An apparatus as claimed in any of claims 20 to 22, wherein the fibres of the cloth are woven.24. An apparatus as claimed in any of claims 20 to 23, wherein the distance between thc fibres is stabilized to reduce or prevent the movement of the fibres relative to one another.25. An apparatus as claimed in claim 24, wherein the fibres are stabilized by ironing of Amendments to the claims have been filed as follows;C LA I NI SAn apparatus for treating a surface of an intermediate transfer member of an indirect printing system, the apparatus comprising a frame to be mounted beneath a section of the intermediate transfer member, a liquid permeable or perforated cloth stretched over the frame, and a jetting assembly mounted beneath the cloth to direct one or more jets of a treatment solution onto the underside of the cloth to deflect the cloth upwards towards the surface of the intermediate transfer member, the treatment solution passing through the cloth to form a liquid film between the cloth aiid the intermediate tnmsfer member that coats the intermediate transfer member with the liquid and prevents the cloth from contacting the surface of the intermediate transfer member.2. An apparatus as claimed in claim 1, wherein the frame is mounted within or above a trough for collecting surplus treatment solution.3, An apparatus as claimed in claim 2, wherein a recirculation pump is provided to draw treatment solution from the trough and supply the treatment solution to the jetting assembly.4. An apparatus as claimed in claim 3, wherein the recirculation pump is selectively capable of drawing the treatment solution from a reservoir or the trough.5. An apparatus as claimed in my of claims 1 to 4, wherein the jetting assembly comprises a plurality ofjets transversely spaced apart from one another and mounted on a manifold configured to ensure equal pressure at each of the individual jets.6. An apparatus as claimed in claim 5, wherein the jetting assembly has a two dimensional array ofjets opening into a plenum chamber within the manifold.7. An apparatus as claimed in any of claims I to 4, wherein the jetting assembly comprises a surface with a plurality of holes transversely spaced apart from one another.8. An apparatus as claimed in any of claims 5 to 7, wherein the shortest distance between any two jets is between 4 mm and 20 mm, or between 6 mm and 15 mm, or between 6 mm and t2 mm, or between 6 mm and 10 mm, or between 8 mm and 10 mm.9. An apparatus as claimed in any of claims 5 to 8, wherein the diameter of the holes in the jetting assembly is between 1 mm and 5 mm, or between 2 mm and 5 mm, or between 1 mm and 2.5 mm.10. An apparatus as claimed in any preceding claim, further including at least one of (i) a pair of squeegee rollers, and (ii) a air knife for removing surplus treatment solution from the surface of the intermediate transfer member.11. An apparatus as claimed in any preceding claim, further comprising backing rollers on the opposite side of the intermediate transfer member from the cloth to prevent movement of the intermediate transfer member away from the cloth.
12. 12. An apparatus as claimed in any preceding claim, further comprising a cooling! heating device for modifying the temperature of the treatment solution.
13. 13. An apparatus as claimed in any preceding claim, wherein the cloth is formed with holes having a diameter between 20 and 150 micrometer (jim).
14. 14. An apparatus as claimed in any preceding claim, wherein the cloth is formed with holes having a diameter of approximately 50 jim, 70 jim, 90 I.Lm, or 110 jim.
15. 15, An apparatus as claimed in any preceding claim, wherein the percent open area of the cloth is between 10 and 50%, or approximately 25%, 35%, or 45%.
16. 16. An apparatus as claimed in my preceding claim, wherein the cloth is formed of monofilament or multifilament fibres that are selected from any one or more of natural and organic fibres, metal-based fibres, glass-based fibres, ceramic-based fibres, thermoplastic polymer fibres aiid synthetic fibres.
17. 17. An apparatus as claimed in claim 6, wherein the cloth is made of thermoplastic polymers comprising at least one polymer selected from the group comprising aramide, high density polyethylene, ultra high density polyethylene and polyesters.
18. 18. An apparatus as claimed in claim 16 or 17, wherein the fibres are resistant to heat ofup to 50°C.
19. 19. An apparatus as claimed in any of claims 16 to 18, wherein the fibres of the cloth are woven.
20. 20. An apparatus as claimed in any of claims 6 to 19, wherein the distance between the fibres is stabilized to reduce or prevent the movement of the fibres relative to one another.
21. 21. An apparatus as claimed in claim 20, wherein the fibres are stabilized by ironing of