Drying of Ink in Digital Printing Using Infrared Radiation Absorbed by Particles Embedded within ITM

Abstract

The system (10, 110) includes: (i) a flexible intermediate transfer member (ITM) (44, 500, 600) including: (a) a first layer (602) disposed on an outer surface of the ITM (44, 500, 600) configured to receive ink droplets to form an ink image thereon and transfer the ink image to a target substrate (50, 51); and (b) a matrix holding particles (622) that receives optical radiation (99) passing through the first layer (602) and transfers the optical radiation (99) to the ITM by absorbing the optical radiation (99). (ii) a flexible intermediate transfer member (ITM) including a stack of a second layer (603), configured to heat the particles (622); (ii) an illumination assembly (113) configured to dry the ink droplets by directing optical radiation (99) to act on the particles (622); and (iii) a temperature control assembly (121) configured to control the temperature of the ITM (44, 500, 600) by directing gas (101) to the ITM (44, 500, 600).

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 62 / 939,726, filed on November 25, 2019, the disclosure of which is incorporated herein by reference.

[0002] The present invention generally relates to digital printing processes, and more particularly to methods and systems for drying ink applied to a surface during a digital printing process.

Background Art

[0003] Optical radiation, such as infrared (IR) and near - infrared radiation, has been used to dry ink in various printing processes.

[0004] For example, U.S. Patent Application Publication No. 2012 / 0249630 describes a process for printing an image that includes printing a substrate with an ink for aqueous inkjet and drying the printed image with a near - infrared drying system. Various embodiments provide processes for inkjet printing and drying of inks having improved absorption in the near - infrared region of the spectrum for improved drying performance of aqueous, hypsochromic inks, as well as inkjet ink sets with improved and balanced near - infrared drying for black and yellow inkjet inks.

Summary of the Invention

Means for Solving the Problems

[0005] Embodiments of the invention described herein provide a system that includes a flexible intermediate transfer member (ITM), an illumination assembly, and a temperature control assembly. The ITM includes a stack of at least (i) a first layer disposed on an outer surface of the ITM configured to receive ink droplets from an ink supply subsystem and form an ink image thereon and transfer the ink image to a target substrate, and (ii) a second layer including a matrix that holds particles at respective given positions. The second layer is configured to receive optical radiation passing through the first layer, and the particles are configured to heat the ITM by absorbing at least a portion of the optical radiation. The illumination assembly is configured to dry ink droplets by directing optical radiation to act on at least a portion of the particles. The temperature control assembly is configured to control the temperature of the ITM by directing a gas toward the ITM.

[0006] In some embodiments, the first and second layers are adjacent to each other, and the particles are disposed at a predetermined distance from each other to uniformly heat the outer surface. In other embodiments, the particles are embedded within the bulk of the second layer at a given distance from the outer surface to uniformly heat the outer surface. In yet other embodiments, the system includes a processor configured to receive a temperature signal indicative of the temperature of the ITM and control at least one of (i) the intensity of the optical radiation and (ii) the flow rate of the gas based on the temperature signal.

[0007] In one embodiment, the system includes one or more temperature sensors disposed at respective given positions with respect to the ITM and configured to generate a temperature signal. In another embodiment, the illumination assembly includes one or more light sources disposed at respective predetermined positions with respect to the ITM. In yet another embodiment, at least one of the light sources is attached adjacent to a print bar of the ink supply subsystem configured to direct ink droplets toward the outer surface.

[0008] In some embodiments, the illumination assembly includes at least an array including a plurality of light sources. In other embodiments, the array includes a plurality of light sources arranged along the moving direction of the ITM.

[0009] In one embodiment, the optical radiation includes infrared (IR) radiation, and at least one of the particles includes carbon black (CB). In another embodiment, the gas includes compressed air, and the temperature control assembly includes a blower configured to supply the compressed air.

[0010] According to one embodiment of the present invention, there is additionally provided a method including directing optical radiation to a flexible intermediate transfer member (ITM) including a stack of at least (i) a first layer disposed on an outer surface of the ITM for receiving ink droplets and forming an ink image thereon and for transferring the ink image to a target substrate, and (ii) a second layer including a matrix holding particles disposed at respective given positions. The optical radiation passes through the first layer, the particles absorb at least a portion of the optical radiation to heat the ITM, and the optical radiation acts on at least a portion of the particles of the second layer to dry the ink droplets on the outer surface. The temperature of the ITM is controlled by directing a gas towards the ITM.

[0011] According to one embodiment of the present invention, there is further provided a method for manufacturing a flexible intermediate transfer member (ITM), the method including generating a first layer disposed on an outer surface of the ITM for receiving ink droplets and forming an ink image thereon and for transferring the ink image to a target substrate. A second layer including a matrix holding particles disposed at respective given positions is applied to the first layer.

[0012] In some embodiments, generating the first layer includes applying the first layer to a carrier, and the method includes removing the carrier from the ITM at least after applying the second layer.

[0013] According to one embodiment of the present invention, a system is further provided that includes a flexible intermediate transfer member (ITM), an illumination assembly, and a temperature control assembly.

[0014] In some embodiments, the illumination assembly includes one or more light sources that are arranged at one or more respective predetermined positions relative to the ITM and configured to direct optical radiation to act on at least a portion of the particles. In other embodiments, at least one of the light sources is attached adjacent to a print bar that directs ink droplets towards the ITM.

[0015] In one embodiment, the illumination assembly includes an array of light sources that are arranged at least along the direction of movement of the ITM and configured to direct optical radiation to act on at least a portion of the particles. In another embodiment, the illumination assembly and the temperature control assembly are packaged within a housing.

[0016] The present invention will be more fully understood from the following detailed description of its embodiments when interpreted in conjunction with the drawings:

Brief Description of the Drawings

[0017]

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[0018] Overview Embodiments of the present invention described below provide an improved technique for drying ink applied to the surface of a substrate during a digital printing process.

[0019] In some embodiments, a digital printing system includes a movable flexible intermediate transfer member (ITM), also referred to herein as a blanket, an imaging station for applying ink droplets to the ITM, an illumination assembly, and a temperature control assembly. The illumination assembly is configured to direct infrared (IR) radiation towards the ITM.

[0020] In some embodiments, the ITM includes a multi-layer stack that includes a release layer disposed on the outer surface of the ITM and facing the illumination assembly and passing through the IR radiation. The release layer is configured to receive ink droplets from a print bar of the imaging station, so that as the ITM moves, the print bar forms a plurality of ink images in respective sections of the release layer. The ITM is then configured to transfer the ink image to a target substrate, such as a sheet or a continuous web.

[0021] In some embodiments, the ITM further includes a layer, herein also referred to as an "IR layer", that is bonded to the release layer and substantially blocks IR radiation. The IR layer has a matrix including a suitable type of silicone and carbon black (CB) particles embedded within the matrix of the IR layer.

[0022] In some embodiments, the IR layer is configured to receive IR radiation passing through the release layer, and in response to the IR radiation, the CB particles are configured to heat at least the IR layer of the ITM and the release layer to dry the ink droplets applied to the release layer.

[0023] In some embodiments, the CB particles are disposed at a given distance from the outer surface of the release layer, at a predetermined distance from each other within the bulk of the IR layer. In such embodiments, due to the low thermal conductivity of the silicone matrix, the heat released from the CB particles can be uniformly dispersed within the IR layer and the release layer, thereby drying the ink uniformly across the outer surface of the release layer.

[0024] Note that the ITM can be damaged at a certain temperature, for example, at about 140 °C or 150 °C. In some embodiments, the temperature control assembly includes a blower configured to supply compressed air directed at the ITM at a temperature of about 30 °C to prevent overheating of the ITM.

[0025] In some embodiments, the digital printing system further includes a processor and a plurality of temperature sensors respectively attached to respective positions on the ITM. Each of the temperature sensors is configured to generate a temperature signal indicative of the temperature of the ITM at the respective position.

[0026] In some cases, the surface of the release layer includes bare sections that do not receive ink droplets between adjacent ink images, and thus, the ITM tends to overheat in the bare sections. In some embodiments, when the ITM moves, the processor is configured to control a temperature sensor to sense the ITM temperature in the bare sections.

[0027] In some embodiments, based on the temperature signal, the processor is configured to control the illumination assembly to adjust the intensity of the IR radiation and / or control the temperature control assembly to adjust the flow rate of the compressed air to keep the temperature of the bare section below a certain temperature described above. In other embodiments, the illumination and cooling assemblies may operate in an open loop, for example, without temperature measurement and adjustment.

[0028] In some embodiments, the image forming station may include a plurality of printing bars, each of which is configured to print a different color of the ink image. Note that some sections of the ink image may include a mixture of the first and second different colors of printed ink, which are individually and successively printed by the first and second printing bars mounted at a predetermined distance from each other on the digital printing system.

[0029] In some embodiments, the digital printing system has a plurality of units, each of which includes one or more IR light sources and a compressed air outlet connected to the temperature control assembly via an exhaust valve. In such embodiments, the unit is mounted between the first and second printing bars to partially dry the ink droplets of the first color applied to the ITM by the first printing bar, so that after the droplets of the second color are applied, the ink droplets of the first and second colors mix with each other on the surface of the release layer.

[0030] In some embodiments, the digital printing system includes an array of a plurality (e.g., 10) of units arranged along the direction of movement of the ITM to achieve complete drying of the ink image printed on the ITM by the printing bars.

[0031] The disclosed technology improves the quality of printed images by obtaining a uniform drying process across the printed image. Further, the disclosed technology improves the productivity of a digital printing system by shortening the drying time of the ink, and thus shortens the cycle time of the printing process.

[0032] System Description FIG. 1 is a schematic side view of a digital printing system 10 according to an embodiment of the present invention. In some embodiments, system 10 includes a rotatable flexible blanket 44 that circulates through an ink supply subsystem, a plurality of drying stations, a printing station 84, and a blanket processing station 52, which is also referred to herein as an image forming station 60. In the context and claims of the present invention, the terms "blanket" and "intermediate transfer member (ITM)" are used interchangeably and refer to a flexible member that includes one or more layers configured to receive an ink image and transfer that ink image to a target substrate, as described in detail below.

[0033] In an operating mode, the image forming station 60 is configured to form a mirror ink image of a digital image 42 on the upper run of the surface of the blanket 44, which is also referred to herein as an "ink image" (not shown) or simply an "image". The ink image is then transferred to a target substrate (e.g., paper, folding carton, multi-layer polymer, or any suitable flexible package in the form of a sheet or continuous web) disposed below the lower run of the blanket 44.

[0034] In the context of the present invention, the term "run" refers to the length or segment of the blanket 44 between any two given rollers over which the blanket 44 is guided.

[0035] In some embodiments, during installation, the blanket 44 may form a continuous blanket loop (not shown) with edges attached to edges. An example of a method and system for installation of seams is described in detail in U.S. Provisional Application No. 62 / 532,400, the disclosure of which is incorporated herein by reference.

[0036] In some embodiments, the image forming station 60 typically includes a plurality of print bars 62, each of which is mounted (e.g., using a slider) on a frame (not shown) positioned at a fixed height above the surface of the upper run of the blanket 44. In some embodiments, each print bar 62 includes an elongate strip of print heads that is the same width as the printing area on the blanket 44 and includes individually controllable print nozzles.

[0037] In some embodiments, the image forming station 60 may include any suitable number of bars 62, and each bar 62 may contain a printing fluid, such as aqueous inks of different colors. The inks typically have visible colors such as, but not limited to, cyan, magenta, red, green, blue, yellow, black, and white. In the example of FIG. 1, the image forming station 60 includes seven print bars 62, but may include four print bars 62 having any selected colors, such as cyan, magenta, yellow, and black.

[0038] In some embodiments, the print head is configured to eject ink droplets of different colors onto the surface of the blanket 44 to form an ink image (not shown) on the outer surface of the blanket 44.

[0039] In some embodiments, the different print bars 62 are spaced apart from each other along a movement axis, represented by arrow 94 and also referred to herein as the direction of movement of the blanket 44. In this configuration, the exact spacing between the bars 62 and the synchronization between the directioning of the ink droplets of each bar 62 and the moving blanket 44 are essential to enable the accurate placement of the image pattern.

[0040] In some embodiments, system 10 includes a dryer 66. In this example, each dryer 66 includes an infrared (IR-based) heater that is configured to raise the temperature of the blanket 44 and evaporate at least a portion of the liquid carrier of the ink to dry a portion of the liquid carrier of the ink applied to the ITM surface. In the example of FIG. 1, the dryer 66 is positioned between the printing bars 62 and is configured to partially dry the ink droplets adhered to the surface of the blanket 44.

[0041] Note that some sections of the ink image printed on the blanket 44 may include a mixture of two or more colors of ink to produce different colors. For example, a mixture of cyan and magenta can result in blue. In this example, the red printing bar can be positioned in front of the yellow printing bar along the direction of movement of the blanket 44 (represented by arrow 94).

[0042] In some embodiments, after injecting red ink at a given location on the surface of the blanket 44, the processor 20 of the system 10 is configured to control one or more of the dryers 66 disposed between the red and yellow printing bars to partially dry the red ink. In such embodiments, after injecting yellow ink at a given location, the partial drying of the red ink allows for the mixing of the red and yellow inks to form an orange color at a given location on the surface of the blanket 44.

[0043] In some embodiments, the blanket 44 has an operating temperature specification. For example, the blanket 44 is configured to operate at a temperature below about 140°C or 150°C in order to prevent damage, such as distortion, to the structure of the blanket 44. In some embodiments, the system 10 further includes a temperature control assembly 121 (described in detail in FIGS. 3 and 4 below), which supplies any suitable gas to the surface of the blanket 44 to attenuate the heat applied by the IR-based heater, thereby maintaining the temperature of the blanket 44 below about 140°C or 150°C or any other certain temperature.

[0044] In some embodiments, the gas can include compressed air, and the temperature control assembly 121 can include a central blower configured to supply the compressed air to a dryer 66 via an exhaust valve. In some embodiments, the dryer 66 includes a combination of the aforementioned IR-based heater for heating the blanket 44 and an air flow channel for cooling the blanket 44. In such embodiments, the compressed air can be used to cool the section of the dryer 66 that is heated by the IR-based heater.

[0045] In some embodiments, the temperature control assembly 121 further includes an exhaust device, which is configured to pump the compressed air used to cool the blanket 44 and the dryer 66 in order to reduce or prevent ink condensation on the product at the surface of the print head.

[0046] In the context and claims of the present disclosure, the term "drying unit" can refer to a device that includes a combination of an IR-based heater for heating the blanket 44 and an air flow channel for cooling the blanket 44. In an example configuration of the system 10, each dryer 66 can include a single drying unit.

[0047] The structures and functions of the temperature control assembly 121 and the dryer 66 are shown in detail in FIGS. 3 and 4 below.

[0048] In some embodiments, this heating between the print bars can serve, for example, to reduce or eliminate condensation on the surface of the print head and / or to process satellites (e.g., residues or small droplets dispersed around the main ink droplets) and / or to prevent clogging of the inkjet nozzles of the print head and / or to prevent the droplets of different color inks on the blanket 44 from mixing with each other unnecessarily.

[0049] In some embodiments, system 10 includes a drying station, herein also referred to as main dryer 64, which is configured to dry the ink image applied to the surface of blanket 44 by image forming station 60. Note that each of dryers 66 is configured to dry ink droplets during the formation of the ink image.

[0050] In an example configuration of system 10, main dryer 64 includes an array of 10 drying units arranged in a row parallel to the direction of movement of blanket 44. In this configuration, main dryer 64 is configured to receive blanket 44 at any suitable temperature, for example, between about 60°C and about 100°C, and after being heated by main dryer 64, to raise the temperature of blanket 44 to any suitable temperature, for example, between about 110°C and about 150°C.

[0051] As it passes through main dryer 64, blanket 44 (which has an ink image thereon) can be exposed to IR radiation and reach the aforementioned temperature (e.g., about 140°C). In some embodiments, main dryer 64 is configured to more completely dry the ink by evaporating most or all of the liquid carrier and leaving only the layer of resin and colorant on the surface of blanket 44 that is heated to the point of becoming a tacky ink film.

[0052] The structure and function of main dryer 64 are shown in detail, for example, in FIG. 4 below.

[0053] In some embodiments, system 10 includes a vertical dryer 96 having an assembly for pumping out (e.g., using a vacuum) gas residues evaporated from the surface of blanket 44. Additionally or alternatively, vertical dryer 96 may include an air knife, which is configured to blow compressed air (or any other suitable gas) onto the surface of blanket 44 to reduce the temperature of blanket 44 and / or remove the aforementioned gas residues from the surface of blanket 44.

[0054] In some embodiments, processor 20 is configured to control the degree of vacuum and / or air pressure in vertical dryer 96 to obtain a desired cleanliness and / or temperature on the surface of blanket 44. Note that the cleanliness of the surface of blanket 44 is particularly important before the ink image printed on blanket 44 enters printing station 84, as described in detail herein.

[0055] In some embodiments, system 10 includes a blanket preheater 98 that includes an IR radiation source (not shown) having an exemplary length of about 1120 mm, or any other suitable length. The IR heat source may include any suitable product that is adapted to a specified output density (depending on the application), supplied, for example, by Heraeus (Hanau, Germany) or by Helios (Novazzano, Switzerland). In such embodiments, blanket preheater 98 is configured to uniformly heat blanket 44 to an exemplary temperature of about 75° C. to prepare blanket 44 for the printing process of the ink image (described above) performed by imaging station 60.

[0056] Note that various elements of the blanket module 70, such as the roller 78, are typically maintained at room temperature (e.g., 25 °C) or any other suitable temperature lower than the temperature typically required to dry the ink sprayed onto the surface of the blanket 44. As a result, the blanket 44 is cooled as it rotates along these elements of the blanket module 70. In some embodiments, the processor 20 controls the vertical dryer 96 for the completion of ink drying (if necessary) before the blanket 44 enters the printing station 84, and further controls the blanket preheater 98 to maintain a specified temperature (e.g., about 75 °C) of the blanket 44 before it enters the imaging station 60.

[0057] In other embodiments, the blanket preheater 98 may include a blower (not shown) configured to supply and direct warm air to heat the surface of the blanket 44. The inventors have found that the use of IR radiation shortens the time (compared to warm air) to obtain the specified temperature of the blanket 44 before receiving the ink image from the imaging station 60. The shortened time is particularly important when starting up the system 10, thus improving the availability and productivity of the system 10. For example, the inventors have found that the blanket 44 can be heated to about 75 °C within a few (e.g., 5) minutes using IR radiation or within about half an hour using warm air.

[0058] In some embodiments, the system 10 includes a blanket module 70 that includes the blanket 44. In some embodiments, the blanket module 70 includes one or more rollers 78, and at least one of the rollers 78 may include an encoder (not shown), and the encoder is configured to record the position of the blanket 44 to control the position of the section of the blanket 44 relative to each printing bar 62.

[0059] In some embodiments, the encoder of roller 78 typically includes a rotary encoder configured to generate a rotary-based position signal indicative of the angular displacement of each roller. Note that in the context and claims of the present invention, the terms "indicative of" and "indication" are used interchangeably without distinction.

[0060] In other embodiments, the blanket module 70 may include any other suitable device for detecting and / or tracking the position of one or more reference points of the blanket 44. For example, the blanket 44 may include markers disposed on the blanket surface and / or etched within the blanket. In such embodiments, the system 10 may include a detection assembly configured to detect the markers and transmit, for example, to the processor 20, a position signal indicative of the position of each marker of the blanket 44.

[0061] In some embodiments, the blanket 44 may include a fabric made of two or more sets of fibers arranged alternately with each other. The fabric has an opacity that varies according to the periodic pattern of the alternately arranged fibers. In some embodiments, the system 10 may include an optical assembly (not shown) having a light source on one side of the blanket 44 and a light detector on the other side of the blanket 44. The optical assembly is configured to irradiate the blanket 44 with light, detect the light passing through the fabric, and derive from the detected light one or more position signals indicative of one or more respective position reference points (e.g., fibers) within the periodic pattern of the fabric.

[0062] In some embodiments, based on the signal, the processor 20 is configured to control the printing process to monitor the states of various elements of the system 10, such as the blanket 44.

[0063] Additionally or alternatively, the blanket 44 may include any suitable type of built-in encoder (not shown) for controlling the operation of the various modules of the system 10. One embodiment of the built-in encoder is described in detail, for example, in U.S. Provisional Application No. 62 / 689,852, the disclosure of which is incorporated herein by reference.

[0064] In some embodiments, the blanket 44 is guided over the roller 78 and also what is herein also referred to as the dancer assembly 74, a powered tension roller. The dancer assembly 74 is configured to control the length of slack in the blanket 44, and its movement is schematically represented by the double-headed arrow. Further, any elongation of the blanket 44 due to aging will not affect the ink image placement performance of the system 10 and will only require further taking up of the slack by applying tension to the dancer assembly 74. In some embodiments, the dancer assembly 74 may be powered.

[0065] The construction and operation of the roller 78 are described in further detail, for example, in U.S. Patent Application Publication No. 2017 / 0008272 and the aforementioned PCT International Publication No. WO2013 / 132424, the disclosures of which are all incorporated herein by reference.

[0066] In other embodiments, the dancer assembly 74 can include a compressed air-based dancer assembly (not shown) that includes an air chamber and lightweight rollers mounted within the air chamber. The air chamber can include an air inlet and an opening that is sized and shaped to fit snugly over the rollers. The compressed air-based dancer assembly can include a controllable blower (other than the blower of the temperature control assembly 121 described above) that is configured to supply compressed air to the air chamber via a given air inlet. The compressed air applies a uniform pressure to the rollers and moves the rollers along the longitudinal axis of the air chamber. As a result, the rollers can protrude from the air chamber through the opening and apply tension to the blanket 44 while the blanket 44 is being rotated. The compressed air-based dancer assembly is further described, for example, in U.S. Provisional Application No. 62 / 889,069, the disclosure of which is incorporated herein by reference.

[0067] In some embodiments, the system 10 can include one or more tension sensors (not shown) disposed at one or more positions along the blanket 44. The tension sensors can be integrated within the blanket 44 or can include sensors external to the blanket 44 that use any other suitable technique for obtaining a signal indicative of the mechanical tension applied to the blanket 44. In some embodiments, the processor 20 and additional controllers of the system 10 are configured to receive signals generated by the tension sensors to monitor the tension applied to the blanket 44 and to control the operation of the dancer assembly 74.

[0068] At the printing station 84, the blanket 44 passes between the impression cylinder 82 and the pressure cylinder 90, which is configured to convey the compressible blanket.

[0069] In some embodiments, system 10 includes a control console 12, which is configured to control a plurality of modules of system 10, such as a blanket module 70, an image forming station 60 disposed on top of the blanket module 70, and a substrate transport module 80 disposed under the blanket module 70 and including one or more printing stations, as described below.

[0070] In some embodiments, console 12 includes a processor 20, typically a general-purpose computer, with appropriate front-end and interface circuitry for interfacing with and receiving signals from a controller of dancer assembly 74 and controller 54 via an electrical cable, herein called cable 57.

[0071] In some embodiments, controller 54, schematically shown as a single device, may include one or more electronic modules mounted at predetermined locations on system 10. At least one of the electronic modules of controller 54 may include an electronic device, such as a control circuit or a processor (not shown), which is configured to control various modules and stations of system 10. In some embodiments, processor 20 and the control circuit may be programmed with software to perform functions used by the printing system and may store data for the software in memory 22. The software may be downloaded in electronic form to processor 20 and the control circuit, for example, via a network, or it may be provided on a persistent tangible medium, such as an optical, magnetic, or electronic memory medium.

[0072] In some embodiments, the console 12 includes a display 34 configured to display data and images received from the processor 20 or input inserted by a user (not shown) using the input device 40. In some embodiments, the console 12 may have any other suitable configuration. For example, alternative configurations of the console 12 and the display 34 are described in detail in U.S. Patent No. 9,229,664, the disclosure of which is incorporated herein by reference.

[0073] In some embodiments, the processor 20 is configured to display on the display 34 a digital image 42 that includes one or more segments (not shown) of the image 42 and / or various types of test patterns that may be stored in the memory 22.

[0074] In some embodiments, the blanket processing station 52 is configured to process the blanket 44, for example, by cooling the blanket, and / or applying a processing fluid to the outer surface of the blanket 44, and / or cleaning the outer surface of the blanket 44. At the blanket processing station 52, the temperature of the blanket 44 can be reduced to a desired temperature value. The processing can be performed by passing the blanket 44 over one or more rollers or blades configured to cool and / or clean and / or apply a processing fluid onto the outer surface of the blanket.

[0075] In some embodiments, the blanket processing station 52 can be disposed adjacent to the printing station 84. Additionally or alternatively, the blanket processing station can include one or more bars (not shown) adjacent to the printing bar 62. In this configuration, the processing fluid can be applied to the blanket 44 by spraying.

[0076] In some embodiments, system 10 includes one or more temperature sensors 92, in this example sensors 92A, 92B, 92C, and 92D, each disposed at a respective given location with respect to blanket 44 and configured to generate a signal indicative of the surface temperature of blanket 44, also referred to herein as a "temperature signal".

[0077] In some embodiments, at least one of temperature sensors 92A - 92D may include an IR - based temperature sensor configured to sense temperature - based IR radiation emitted from the surface of blanket 44. In other embodiments, at least one of temperature sensors 92A - 92D may include any other suitable type of temperature sensor.

[0078] In the configuration example of FIG. 1, system 10 includes: (i) a first temperature sensor 92A disposed in close proximity to a blanket tension drive roller, referred to herein as roller 78A; (ii) a second temperature sensor 92B disposed between the first printing bar 62 and a first dryer, referred to herein as pre - heater 66A; (iii) a third temperature sensor 92C disposed between the right - hand printing bar 62 (in the direction of movement) and the main dryer 64; and (iv) a fourth temperature sensor 92D disposed in close proximity to a blanket control drive roller, referred to herein as roller 78B.

[0079] In some embodiments, temperature sensor 92A, disposed between blanket pre - heater 98 and imaging station 60, is configured to detect the temperature of blanket 44 before it enters imaging station 60. In one embodiment, temperature sensor 92B is positioned behind (in the direction of movement indicated by arrow 94) pre - heater 66A to measure the temperature of blanket 44 before it enters the first printing bar.

[0080] In some embodiments, the controller 54 and / or the processor 20 are configured to receive a temperature signal from one or more of the aforementioned temperature sensors and control the printing process based on the received temperature signal, as described in detail below.

[0081] In other embodiments, the temperature signal from the temperature sensor 92B is sufficient to control the start of a new cycle of the printing process performed by the image forming station 60, such that the temperature sensor 92A may be redundant and thus may be removed from the configuration of the system 10.

[0082] Note that the temperature of the blanket 44 is important for the quality of the printing process performed by the image forming station 60. In some embodiments, the temperature of the blanket 44 is set to a predetermined temperature (e.g., about 70° C.) to (i) dry the first color ink droplets applied to the ITM by the first printing bar and (ii) return the blanket temperature (cooled by ink droplets having a typical temperature of about 30° C. or 35° C.) to the predetermined temperature of about 70° C.

[0083] In some embodiments, in response to heating of the blanket, a controlled amount of vapor of the first printing fluid (e.g., ink) typically evaporates from the blanket surface without adhering to the nozzles of any of the printing bars 62. Further, based on the required color matching of the ink image, the temperature of the first ink is controlled by the temperature of the blanket such that after the second color ink droplets are applied, the first and second color ink droplets mix with each other to form the required color on the surface of the release layer of the blanket 44.

[0084] In the example configuration of system 10, temperature sensors 92A - 92D are placed after every event or sub - step of the printing process that affects or can affect the temperature of blanket 44. In some embodiments, based on the temperature signals received from the temperature sensors, processor 20 (and / or controller 54) is configured to control a power source (not shown) to adjust the output density applied to one or more infrared sources of each heater (e.g., as shown in FIG. 3 below).

[0085] In such embodiments, processor 20 is configured to use a closed - loop approach in both feedback and feed - forward modes to adjust the output density applied to the dryer. The term "feedback" refers to adjusting the output density in a given dryer based on the temperature measured after using the given dryer to obtain the temperature required in a subsequent section of the blanket. The term "feed - forward" refers to adjusting the output density based on the temperature measured before using the dryer to correct for deviations from the required temperature. In the example configuration of FIG. 1, processor 20 is configured to control the output density applied to one or more IR sources (if any) of pre - heaters 98 and 66A using closed - loop feedback and feed - forward modes respectively, based on the temperature signals received from temperature sensor 92A. For example, if the signal received from sensor 92A indicates that the temperature of the first section of blanket 44 is below the pre - defined temperature of 70°C, processor 20 controls the power source to: (i) increase the output density applied to pre - heater 66A to obtain 70°C in the first section of blanket 44 (using the feed - forward mode), and (ii) increase the output density applied to pre - heater 98 to obtain 70°C in the second section of blanket 44, following the first section (using the feedback mode).

[0086] In some embodiments, after adjusting the output density applied to the power supply(ies) of the preheater 66A, the processor 20 receives a temperature signal from the temperature sensor 92B. In the case where the temperature is about 70° C., the processor 20 enables the first printing bar of the image forming station 60 to apply droplets of the first ink to the blanket 44. However, in the case where the temperature measured by the temperature sensor 92B is significantly different from about 70° C. (e.g., about 50° C.), the processor 20 blocks the printing bar of the image forming station 60 from applying ink droplets to the blanket 44 and controls the power supply to adjust the temperature of the blanket to a predefined temperature of about 70° C. Only after achieving 70° C. does the processor 20, as described above, control the image forming station 60 to resume the printing process using the printing bar 62.

[0087] In some embodiments, using the techniques described above, the processor 20 is configured to (i) control the output density applied to the main dryer 64 based on the temperature signal received from the temperature sensor 92C and (ii) control the output density applied to the vertical dryer 96 based on the temperature signal received from the temperature sensor 92D. Additionally or alternatively, the processor 20 may use the signal received from the temperature sensor 92D to adjust the output density applied to the main dryer 64.

[0088] In some embodiments, in response to receiving a temperature signal, processor 20 is configured to control the temperature of the blanket by adjusting the flow rate of compressed air within the air flow channels, as shown in and described in detail in FIGS. 3 and 4 below. It should be noted that processor 20 is configured to perform closed-loop control regarding the associated blower of system 10 using feedforward and feedback techniques. For example, if the measured temperature is above the required temperature of blanket 44, processor 20 is configured to control the blower to increase the flow of compressed air applied to blanket 44. Similarly, if the measured temperature is below the required temperature of blanket 44, processor 20 is configured to control the blower to decrease the flow of compressed air applied to blanket 44.

[0089] In some embodiments, processor 20 is configured to simultaneously control both the intensity of IR radiation (by adjusting the output density supply) and the flow of compressed air to control the temperature of blanket 44. For example, in response to receiving a signal from temperature sensor 92D indicating that the temperature of blanket 44 is significantly different from approximately 140° C., processor 20 may control at least one of main dryer 64 and vertical dryer 96 to adjust the intensity of IR radiation and / or the flow of compressed air to obtain a specified temperature of approximately 140° C. on blanket 44.

[0090] In other embodiments, based on the aforementioned temperature signal, processor 20 is further configured to control the operation of other assemblies and stations of system 10, such as but not limited to blanket processing station 52. Examples of such processing stations are described, for example, in PCT International Publications WO2013 / 132424 and WO2017 / 208152, the disclosures of which are hereby incorporated by reference in their entirety.

[0091] Additionally or alternatively, before inkjet printing at the imaging station, the processing fluid may be applied to blanket 44 by spraying.

[0092] In the example of FIG. 1, the station 52 is attached between the printing station 84 and the image forming station 60, but the station 52 can be attached adjacent to the blanket 44 at any other or additional one or more suitable positions between the printing station 84 and the image forming station 60. As described above, the station 52 can alternatively or additionally include a bar adjacent to the image forming station 60.

[0093] In the example of FIG. 1, the impression cylinder 82 presses the ink image onto the target flexible substrate, such as an individual sheet 50, that has been conveyed from the input stack 86 to the output stack 88 via the impression cylinder 82 by the substrate conveyance module 80.

[0094] In some embodiments, the lower run of the blanket 44 selectively interacts with the impression cylinder 82 at the printing station 84 to press an image pattern onto the target flexible substrate that is compressed between the blanket 44 and the impression cylinder 82 by the action of the pressure of the pressure cylinder 90. In the case of the simplex printer shown in FIG. 1 (i.e., printing on one side of the sheet 50), only one printing station 84 is required.

[0095] In other embodiments, the module 80 can include two or more impression cylinders to enable one or more double-sided prints. The configuration of two impression cylinders also enables the execution of single-sided prints at twice the speed of double-sided print printing. In addition, mixed lots of single-sided and double-sided prints can be printed. In alternative embodiments, different configurations of the module 80 can be used for printing on a continuous web substrate. Detailed descriptions and various configurations of double-sided printing systems and systems for printing on a continuous web substrate are provided, for example, in U.S. Pat. Nos. 9,914,316 and 9,186,884, PCT International Publication No. WO2013 / 132424, U.S. Patent Application Publication No. 2015 / 0054865, and U.S. Provisional Application No. 62 / 596,926, the disclosures of which are all incorporated herein by reference.

[0096] As briefly described above, the sheet 50 or continuous web substrate (not shown) is conveyed from the input stack 86 by the module 80 and passes through a nip (not shown) disposed between the impression cylinder 82 and the pressure cylinder 90. Within the nip, the surface of the blanket 44 carrying the ink image is firmly pressed against the sheet 50 (or other suitable substrate) by, for example, a compressible blanket (not shown) of the pressure cylinder 90, whereby the ink image is applied onto the surface of the sheet 50 and cleanly separated from the surface of the blanket 44. Thereafter, the sheet 50 is conveyed to the output stack 88.

[0097] In the example of FIG. 1, the roller 78 is positioned on the upper run of the blanket 44 and is configured to maintain the blanket 44 taut as it passes adjacent to the imaging station 60. Further, it is particularly important to control the speed of the blanket 44 under the imaging station 60 in order to obtain accurate ejection and deposition of ink droplets onto the surface of the blanket 44, and thereby placement of the ink image, by the forming station 60.

[0098] In some embodiments, the impression cylinder 82 is periodically engaged with and released from the blanket 44 to transfer the ink image from the moving blanket 44 to a target substrate passing between the blanket 44 and the impression cylinder 82. In some embodiments, the system 10 is configured to apply torque to the blanket 44 using the aforementioned roller and dancer assemblies to maintain the upper run taut and substantially isolate the upper run of the blanket 44 from being affected by mechanical vibrations occurring in the lower run.

[0099] In some embodiments, system 10 includes an image quality management station 55, also referred to herein as an automatic quality management (AQM) system, which functions as a closed-loop inspection system integrated within system 10. In some embodiments, station 55 can be positioned adjacent to impression cylinder 82 or at any other suitable location within system 10, as shown in FIG. 1.

[0100] In some embodiments, station 55 includes a camera (not shown) configured to acquire one or more digital images of the aforementioned ink images printed on sheet 50. In some embodiments, the camera can include any suitable image sensor, such as a contact image sensor (CIS) or a complementary metal-oxide semiconductor (CMOS) image sensor, and a scanner including a slit having a width of about one meter or any other suitable width.

[0101] In the context of the present disclosure and claims, the terms “about” or “approximately” with respect to any numerical value or range indicate a suitable dimensional tolerance that allows the component parts or assemblies to function for their intended purpose as described herein. For example, “about” or “approximately” can refer to a range of values within ±20% of the recited value. For example, “about 90%” can refer to a range of values from 72% to 100%.

[0102] In some embodiments, station 55 can include a spectrophotometer (not shown) configured to monitor the quality of the ink printed on sheet 50.

[0103] In some embodiments, the digital images acquired by the station 55 are transmitted to a processor, such as the processor 20 or any other processor of the station 55, which is configured to evaluate the quality of each printed image. Based on that evaluation and the signals received from the controller 54, the processor 20 is configured to control the operation of the modules and stations of the system 10. In the context and claims of the present invention, the term "processor" refers to any processing device, such as the processor 20 or any other processor or controller connected to or integrated with the station 55, which is configured to process the signals received from the camera and / or spectrophotometer of the station 55. It should be noted that the signal processing operations, control-related instructions, and other computational operations described herein may be executed by a single processor or may be shared among multiple processors of one or more respective computers.

[0104] In some embodiments, the station 55 is configured to inspect the quality of printed images and test patterns to monitor various attributes, such as, but not limited to, complete image positioning with the sheet 50, color-to-color (C2C) positioning, printed geometries, image uniformity, color profiles and linearity, and the functionality of the print nozzles. In some embodiments, the processor 20 is configured to automatically detect geometric distortions or other errors in one or more of the aforementioned attributes. For example, the processor 20 is configured to compare a design version of a given digital image (also referred to herein as the "master" or "source image") with a digital image of the printed version of the given image acquired by the camera.

[0105] In other embodiments, the processor 20 may apply any suitable type of image processing software, for example, to a test pattern, to detect distortions indicative of the aforementioned errors. In some embodiments, the processor 20 is configured to analyze the detected distortions in order to apply corrective measures to a malfunctioning module and / or to supply instructions to another module or station of the system 10 to correct the detected distortions.

[0106] In some embodiments, the processor 20 is configured to detect deviations in the profile and linearity of the printed color based on signals received from the spectrophotometer of the station 55.

[0107] In some embodiments, the processor 20 is configured to detect various types of defects based on signals acquired by the station 55: (i) in the substrate (e.g., blanket 44 and / or sheet 50), such as scratches, pinholes, and damaged edges, and (ii) printing-related defects such as irregular color spots, satellites, and spatters.

[0108] In some embodiments, the processor 20 is configured to detect these defects by comparing sections of the printed material with respective reference sections of the original design, also referred to herein as the master. The processor 20 is further configured to classify the defects and, based on the classification and predetermined criteria, reject the sheet 50 having defects that are not within the specified predetermined criteria.

[0109] In some embodiments, the processor of station 55 is configured to determine, for example, whether to stop the operation of system 10 if the defect density exceeds a specified threshold. As described above, the processor of station 55 is further configured to initiate corrective measures in one or more of the modules and stations of system 10. The corrective measures can be performed on-the-fly (while system 10 continues the printing process) or offline, by stopping the printing operation and correcting problems within each module and / or station of system 10. In other embodiments, any other processor or controller of system 10 (e.g., processor 20 or controller 54) is configured to initiate corrective measures or stop the operation of system 10 if the defect density exceeds a specified threshold.

[0110] Additionally or alternatively, processor 20 is configured to receive, for example, signals from station 55 indicating additional types of defects and problems in the printing process of system 10. Based on these signals, processor 20 is configured to automatically estimate the pattern placement accuracy and the level of additional types of defects not described above. In other embodiments, any other suitable method for inspecting the patterns printed on sheet 50 (or any other substrate described above) can also be used, for example, an external (e.g., offline) inspection system, or any type of measurement fixture and / or scanner. In these embodiments, based on the information received from the external inspection system, processor 20 is configured to initiate any suitable corrective measures and / or stop the operation of system 10.

[0111] The configuration of system 10 is provided simplified as an example purely for clarity of the present invention. The components, modules and stations described in the aforementioned printing system 10, as well as additional components and configurations, are described in detail, for example, in U.S. Pat. Nos. 9,327,496 and 9,186,884, PCT International Publications WO2013 / 132438, WO2013 / 132424 and WO2017 / 208152, and U.S. Patent Application Publications 2015 / 0118503 and 2017 / 0008272, the disclosures of all of which are incorporated herein by reference.

[0112] The specific configuration of system 10 is shown as an example to illustrate the specific problems addressed by embodiments of the present invention and to illustrate the application of these embodiments in enhancing the performance of such a system. However, embodiments of the present invention are in no way limited to this particular type of system example, and the principles described herein can be equally applied to any other type of printing system.

[0113] For example, in other embodiments, dryer 66 and / or blanket preheater 98 may include two or more IR radiation sources. Similarly, main dryer 64 may include any other suitable number of drying units, or any other suitable type of ink drying device.

[0114] In alternative embodiments, at least one of the dryers may include a radiation source configured to emit radiation other than IR. For example, near-infrared, visible light, ultraviolet (UV), or any other suitable wavelength or wavelength range.

[0115] FIG. 2 is a schematic side view of a digital printing system 110 according to some embodiments of the present invention. In some embodiments, system 110 includes an image forming station 160, a drying station 64, a vertical dryer 96, a blanket preheater 98, and a blanket 44 that circulates through a blanket processing station 52, as described in FIG. 1 above.

[0116] In some embodiments, system 110 is configured to transfer an ink image from a moving blanket 44 to a continuous flexible web substrate, herein referred to as web 51, which is the target substrate of system 110. In such embodiments, system 110 includes a substrate conveyance module 100, which is configured to carry web 51 from a pre-print buffer unit 186 through one or more printing stations 85 for receiving the ink image from blanket 44 to a post-print buffer unit 188.

[0117] Each printing station 85 can have any configuration suitable for transferring an ink image from blanket 44 to web 51. In some embodiments, the lower run of blanket 44 selectively interacts with a impression cylinder 192 at printing station 85 to press an image pattern onto web 51 compressed between blanket 44 and impression cylinder 192 by the action of the pressure of pressure cylinder 190. For simplex printing (i.e., printing on one side of web 51) as shown in FIG. 2, only one printing station 85 is required. For duplex printing (i.e., printing on both sides of web 51), not shown in FIG. 2, system 110 can include, for example, two printing stations 85.

[0118] In some embodiments, substrate conveyance module 100 can have any suitable configuration for carrying web 51. One example of an embodiment is described in detail in U.S. Provisional Application No. 62 / 784,576 (Applicant Docket No. LCP16 / 001, Attorney Docket No. 1373-1009), the disclosure of which is incorporated herein by reference.

[0119] In some embodiments, the web 51 includes one or more layers of any suitable material, such as aluminum foil, paper, polyester (PE), polyethylene terephthalate (PET), biaxially oriented polypropylene (BOPP), oriented polyamide (OPA), biaxially oriented polyamide (BOPA), other types of oriented polypropylene (OPP), a shrink film, also referred to herein as a polymeric plastic film, or any other material suitable for flexible packaging in the form of a continuous web, or any suitable combination thereof, such as, for example, in a multilayer structure. The web 51 can be used in a variety of applications, including, but not limited to, food packaging, plastic bags and tubes, labels, decoration, and flooring.

[0120] In some embodiments, the imaging station 160 typically includes a plurality of print bars 62, each of which is mounted (e.g., using a slider) on a frame (not shown) positioned at a fixed height above the upper run surface of the blanket 44. In some embodiments, as also described in FIG. 1 above, each print bar 62 includes a plurality of print heads arranged to cover the width of the printing area on the blanket 44 and includes individually controllable print nozzles.

[0121] In some embodiments, the imaging station 160 can include any suitable number of print bars 62, and each print bar 62 can contain a printing fluid as described above, such as an aqueous ink. The ink typically has a visible color, such as, but not limited to, cyan, magenta, red, green, blue, yellow, black, and white. In the example of FIG. 2, the imaging station 160 includes a white print bar 61 and four print bars 62 having any selected colors, such as cyan, magenta, yellow, and black.

[0122] In some printing applications, the white ink is applied to the surface of the web 51 before all other colors, and in some cases, it is important that the white does not mix with the inks of other colors within at least some sections of the web 51.

[0123] In some embodiments, system 110 includes a white ink drying station, herein referred to as white dryer 97, which is configured to dry the white ink applied to the surface of blanket 44 by image forming station 160. In such embodiments, white dryer 97 may include five drying units, each of which includes the aforementioned IR-based heater for heating blanket 44 and a combination of one or more air flow channels for cooling blanket 44.

[0124] In other embodiments, white dryer 97 may include any other configuration suitable for drying white ink. For example, white dryer 97 may include any other number of drying units, or may include any other suitable drying device using any other suitable drying technique.

[0125] In one embodiment, white dryer 97 is controlled by processor 20 and / or controller 54 and is configured to dry the white ink applied to the surface of blanket 44 by white print bar 61. In this embodiment, processor 20 and / or controller 54 are configured to control white dryer 97 to partially or completely dry the white ink applied to the surface of blanket 44.

[0126] In the configuration of system 110, white dryer 97 replaces one dryer 66 used for drying inks of any color other than white. In this configuration, system 110 does not have a print bar between white dryer 97 and the first dryer 66. However, in other embodiments, it should be noted that system 110 may have any suitable printing component (e.g., a print bar) or sensing component (e.g., a temperature sensor or any other type of sensor) between white dryer 97 and the first dryer 66.

[0127] In other embodiments, system 110 may include any other suitable type of dryer for drying or partially drying inks of any specific color other than white.

[0128] For other printing applications, the white ink can be applied to the surface of the web 51 after all other colors. In an alternative embodiment, the white ink can be applied to the surface of the web 51 using a subsystem external to the system 110 or integrated with the system 110. In such an embodiment, the white ink is applied to the surface of the web 51 using the imaging station 160, before or after applying the other colors to the surface of the blanket 44, and in particular, before or after applying the other colors to the surface of the web 51 within the printing station 85.

[0129] In some embodiments, the temperature sensor 92B is disposed between the aforementioned first dryer 66 and the printing bar 62 to check the surface temperature of the blanket 44 before applying ink having a color other than white using the printing bar 62. Further, the temperature sensor 92B is disposed between the last printing bar of the imaging station 160 and the main dryer 64. Note that the temperature sensors 92A, 92C, and 92D are disposed in the same positions in both the system 110 and the system 10 of FIG. 1 above. However, the temperature sensor 92B is disposed along the path of the blanket 44, after the white printing and drying (here, after the printing bar 61 and the dryer 97), and before the first printing bar 62 for a color other than white (e.g., cyan, magenta, yellow, black, or any other color).

[0130] In some embodiments, the temperature sensors 92B, 92C, and 92D are disposed after processing substeps that typically affect or can affect the temperature of the blanket 44, as also described in FIG. 1 above.

[0131] In some embodiments, system 110 may include a drying station, herein referred to as lower dryer 75, which is configured to emit infrared light or light of any other suitable frequency, or frequency range, to dry the ink image formed on blanket 44 using the techniques described above. In the example of FIG. 2, lower dryer 75 may include five drying units, each of which includes a combination of the aforementioned IR-based heaters for heating blanket 44 and one or more air flow channels for cooling blanket 44.

[0132] In some embodiments, system 110 includes a temperature sensor 92E disposed between lower dryer 75 and printing station 85, typically in very close proximity to lower dryer 75.

[0133] In some embodiments, processor 20 (and / or controller 54) is configured to control a power supply (not shown) described in FIG. 1 above to adjust the output density applied to one or more infrared sources of each heater and / or dryer (shown in FIGS. 3 and 4 below) to maintain a predefined temperature of blanket 44 along each section of system 110.

[0134] In some embodiments, using the techniques described in FIG. 1 above, processor 20 (and / or controller 54) is configured to perform closed-loop control regarding the temperature profile of blanket 44 along each section of system 110. The control is performed based on temperature signals received from at least one of temperature sensors 92A - 92E, and based on the temperature signals, processor 20 controls the output density applied to the IR power supplies of each IR-based heater (e.g., one or more of heaters 98 and dryers 97, 66, 64, 96, and 75).

[0135] In other embodiments, the lower dryer 75 may include any other suitable configuration suitable for drying the ink in the lower run of the blanket 44 before the blanket enters the printing station 85.

[0136] In some embodiments, the processor 20 and / or the controller 54 are each configured to control the respective dryers of the system 10 (shown in FIG. 1) and the system 110 (shown in FIG. 1).

[0137] The control may be performed based on various conditions of a particular digital printing application. For example, based on the type, order, and surface coverage level of the colors applied to the surface of the blanket 44, and based on the type of the blanket 44 and the target substrate (e.g., the sheet 50 or the web 51).

[0138] The term "coverage level" refers to the amount of color applied to the surface of the blanket 44. For example, a coverage level of 250% refers to two and a half times the ink layer applied to a predefined section (or the entire area) of the ink image printed on the blanket 44 and then designated for transfer to the target substrate. It should be noted that the two and a half times ink layer may include three or more of the aforementioned colors of ink described above. It will be understood that larger coverage levels typically require a larger bundle of IR irradiation and, therefore, a higher air flow to cool the blanket 44.

[0139] In other embodiments, the ink drying process can be carried out in an open loop, for example, without controlling at least one of (a) the intensity of the IR radiation and (b) the flow rate of the compressed air by the temperature control assembly 121. For example, as part of a process recipe for printing a particular image, the recipe parameters can include the coverage level of the ink image, and the processor 20 and / or the controller 54 can preset one or more of (a) the intensity of the IR radiation and (b) the flow rate of the compressed air by the temperature control assembly 121 to dry the ink and maintain the temperature of the blanket 44 below a specified temperature (e.g., about 140 °C or about 150 °C).

[0140] A particular configuration of the system 110 is shown by way of example in order to illustrate the particular problems addressed by embodiments of the present invention and to illustrate the application of these embodiments in enhancing the performance of such a system. However, embodiments of the present invention are in no way limited to this particular type of system example, and the principles described herein can be equally applied to any other type of printing system.

[0141] A drying unit mounted within the image fixing unit FIG. 3 is a schematic side view of a dryer 66 for drying the ink applied by the printing bar 62 in accordance with an embodiment of the present invention. In some embodiments, the dryer 66 includes a single drying unit, such as the drying unit briefly described in FIG. 1 above and further described in detail herein.

[0142] In some embodiments, the dryer 66 has a blower and includes one or more openings to an air inlet channel (AIC) 122 configured to supply compressed air 101 (or any other suitable type of gas) to the dryer 66.

[0143] In some embodiments, the dryer 66 further includes one or more openings to an air outlet channel (AOC) 123 having an air extraction device (e.g., a suitable type of vacuum or negative pressure pump) configured to extract compressed air 101, as described herein, at least after cooling of the blanket 44.

[0144] In the concepts and claims of the present disclosure, the term "temperature control assembly" refers to at least one of the AIC 122 and the AOC 123 or a combination thereof and is configured to direct compressed air 101 (or any other suitable type of gas) toward the outer surface 106 of the blanket 44 to reduce the temperature of the blanket 44 to below a specified temperature (e.g., about 140 °C or about 150 °C), as described herein.

[0145] In some embodiments, the dryer 66 is typically disposed within the imaging station 60, and the main dryer 64 is disposed between the imaging station 60 and the printing station 84 such that a drying process of an ink image applied to the blanket 44 is performed before the ink image is transferred to a target substrate (e.g., the sheet 50) within the printing station 84. Note that the temperature control assembly 121 is configured to supply compressed air 101 to the dryer 66 and the main dryer 64 via, for example, a pipe or tube (not shown) to control the temperature of the blanket 44 within the aforementioned specified temperature range. In other embodiments, the system 10 may include a plurality of AICs 122 and / or AOCs 123, e.g., a first set of AIC 122 and AOC 123 for the dryer 66 and a second set of AIC 122 and AOC 123 for the main dryer 64. In alternative embodiments, the system 10 may include any other suitable configuration of the AIC 122 and / or AOC 123 controlled by the processor 20 and / or a local controller synchronized with and / or controlled by the processor 20.

[0146] In some embodiments, the dryer 66 includes one or more IR-based heaters, in this example, an illumination assembly 113 having an IR radiation source, simply referred to herein as source 111. In the example of FIG. 3, the dryer 66 includes two pairs of sources 111 disposed within two respective cavities of the dryer 66. Each source 111 is configured to direct a beam 99 of IR radiation toward the blanket 44. For example, each source 111 is configured to emit an output density between about 30 w / cm and about 300 w / cm toward the surface 106 of the blanket 44.

[0147] In other embodiments, the dryer 66 may include any other suitable number of sources 111 (or any other suitable type of one or more light sources configured to emit light of IR or any other suitable wavelength or wavelengths) having any suitable geometry and arranged in any suitable configuration.

[0148] In some embodiments, the dryer 66 may include one or more reflectors 108 coupled between the source 111 and the cavity of the dryer 66. The reflector 108 is configured to reflect the beam 99 of light emitted from the source 111 toward the blanket 44 in order to improve the efficiency and speed of the IR-based drying process and to reduce the amount of IR radiation (and thus, the excess heating) applied to the dryer 66 by the beam 99.

[0149] For example, each reflector 108 may reflect about 90% of the beam 99 of light toward the blanket 44 and may absorb the remaining 10%, which may raise the temperature within the cavity of the dryer 66.

[0150] In some embodiments, the dryer 66 includes a heat transfer assembly (HTA) 104, which includes a heat conducting material (e.g., copper, aluminum, or other metal or non-metal material) disposed around the reflector 108 as heat conducting ribs and traces. The HTA 104 is configured to dissipate excess heat from each cavity of the dryer 66.

[0151] In the example configuration of dryer 66, compressed air 101 enters the dryer 66 via AIC122 at an exemplary temperature of about 30°C or any other suitable temperature between about 5°C and about 100°C. Thereafter, the compressed air 101 flows through the internal channels of the dryer 66 to transport heat from HTA104 (e.g., by heat convection), and then is directed through the opening 95 of the dryer 66 to the location 102 on the surface 106. The compressed air 101 flows over the surface 106 to transfer heat from the blanket 44, and then the AOC123 extracts the compressed air 101 from the surface 106 through the air outlet passage 112 of the dryer 66 to maintain the temperature of the blanket 44 below the aforementioned specified temperature.

[0152] As shown in FIGS. 1 - 3, the dryer 66 can be disposed adjacent to the printing bar 62, typically between two adjacent printing bars 62. In some embodiments, the dryer 66 is configured to extract the compressed air 101 via the air outlet passage 112 such that the compressed air 101 does not physically contact either of the printing bars 62. Note that the compressed air 101 contains vapors of ink components that can interact with the printing process. For example, such vapors can partially or completely block the nozzles of the printing bar 62, which can degrade the quality of the printed image (e.g., ink missing if the nozzle is completely blocked, or defects including clusters of dried ink if the nozzle is partially blocked).

[0153] In some embodiments, the structure of the dryer 66 prevents the compressed air 101 entering from AIC122 from mixing with the compressed air 101 flowing into the surface 106 through the opening 95. As described above, after flowing through the opening 95, the compressed air 101 is forced to flow into the AOC123 through the air outlet passage 112. In other words, the outflow air that may contain ink residues and the inflow air for cooling the surface 106 never mix with each other inside the dryer 66.

[0154] In some embodiments, the light beam 99 is directed to position 102 based on the position of the source 111 within the cavity of the dryer 66. Similarly, the dryer 66 is designed such that the compressed air 101 is directed to position 102 to cool the blanket 44. Each drying unit of the dryer 66 includes two sets of IR-based heating and compressed-air-based cooling, with an air outlet passage 112 therebetween. In this configuration, note that in order to prevent contact between the compressed air 101 and the printing bar 62, the compressed air 101 flows into the blanket 44 from the side of the dryer 66 and exits from the blanket 44 through the air outlet passage 112 positioned at the center of the dryer 66.

[0155] In some embodiments, the distance 131, which is the distance between the dryer 66 and the surface 106, can be used to control the amount of IR-based heating and air-based cooling. In principle, a smaller distance 131 accelerates the heating rate of the blanket 44. In other words, when the distance 131 is small, in response to the IR-based heating, the blanket 44 reaches the specified temperature (e.g., about 140 °C or about 150 °C) more quickly, resulting in the ink on the surface of the blanket 44 drying more rapidly.

[0156] In some embodiments, the distance 131 can be predetermined, for example, when mounting the dryer 66 on the frame of the system 10 and / or the system 110. In other embodiments, the distance 131 can be controlled using any suitable mounting base for moving the dryer 66 relative to the blanket 44.

[0157] In some embodiments, by controlling the distance 131, the processor 20 can control the intensity and uniformity of the output density applied by the source 111 to a given section of the blanket 44. For example, a greater distance 131 can result in a smaller output density applied to a given section of the blanket 44, but can improve the uniformity of heating within and in the immediate vicinity of that given section. Similarly, the proximity between the blanket 44 and the dryer 66 can affect the level of cooling by the dryer 66. For example, a greater distance 131 reduces the effectiveness of cooling of the blanket surface by the compressed air 101.

[0158] As described above, when the blanket 44 is moved in the direction indicated by the arrow 94, the printing bar 62 disposed adjacent to the dryer 66 injects ink droplets onto the blanket 44. In some embodiments, further described in detail in FIG. 6 below, the dryer 66 and the blanket are designed to be configured such that the light beam 99 heats the blanket 44, and the elevated temperature induces evaporation of the liquid carrier of the ink to dry or partially dry the ink on the surface 106. Note that the light beam 99 is directed at the blanket 44 to raise the temperature of the blanket, not at the ink for evaporation. Similarly, the compressed air 101 is directed at the blanket 44 by the AIC 122 and extracted from the blanket by the AOC 123 to lower the temperature of the blanket 44.

[0159] The specific configuration of the drying unit of the dryer 66 is provided as an example to illustrate certain problems, such as the partial drying of the ink image applied to the blanket 44 and the cooling of the blanket, which are addressed by embodiments of the present invention, and to illustrate the application of these embodiments in enhancing the performance of digital printing systems such as the aforementioned systems 10 and 110. However, embodiments of the present invention are in no way limited to this specific configuration and type of drying unit example, and the principles described herein can be equally applied to any other type of drying unit within a digital printing system or any other type of printing system.

[0160] In other embodiments, the compressed air 101 can be used only to lower the temperature of the blanket 44, while a separate (e.g., dedicated) cooling device can be used to cool the HTA 104.

[0161] Dryer including a plurality of drying units FIG. 4 is a schematic side view of the main dryer 64 according to an embodiment of the present invention. In some embodiments, the main dryer 64 includes a plurality of drying units 222 and an air outlet passage 130 between each pair of adjacent drying units 222.

[0162] Referring now to the inserted view 133, a pair of drying units 222 and the air outlet passage 130 disposed therebetween are shown. Each drying unit 222 is disposed at a distance 132 from the surface 106 of the blanket 44. Note that the distance 132 can be different from the distance 131 and can be controllable, for example, using the mounting base described in FIG. 3 above. Alternatively, the distance 132 can be predetermined based on the distance between the frame of the image forming station and the position of the blanket 44.

[0163] In some embodiments, each drying unit 222 has two cavities, each of which has a pair of sources 111 of the illumination assembly 113, and they are configured to direct light rays 99 to heat the blanket 44 using the techniques described for the dryer 66 in FIG. 3 above. The drying unit 222 further includes a heat transfer assembly (HTA) 124 that has the same cooling function as the HTA 104 but has a different structure adapted to the structure of the drying unit 222.

[0164] In some embodiments, compressed air 101 enters the drying unit 222 via the AIC 122 at an exemplary temperature of about 30° C. or at any other suitable temperature, for example, as described for the dryer 66 in FIG. 3 above, and flows through the HTA 124 to cool the drying unit 222. Thereafter, the compressed air 101 exits the drying unit 222 through the opening 195, is directed towards the blanket 44 to lower the temperature of the blanket 44 as described for the dryer 66 in FIG. 3 above, and is pumped from the blanket 44, through the air outlet passage 130, towards the AOC 123 using the same techniques described in FIG. 3 above.

[0165] Note that in this configuration, the compressed air 101 flows out from the center of the drying unit 222 towards the blanket 44 and is pumped out through the air outlet passage 130 disposed on the side of the drying unit 222 from the blanket 44.

[0166] In the example of FIG. 4, the main dryer 64 includes nine drying units 222 and two halves of the drying unit 222 at both ends of the main dryer 64. In this configuration, the main dryer 64 includes ten air outlet passages 130, which improves the extraction of the compressed air 101 compared to a set of ten full - size drying units 222 (not shown) having a total of nine air outlet passages 130.

[0167] In some embodiments, the processor 20 and / or the controller 54 receives temperature signals from one or more of the temperature sensors 92A-92E and, based on the temperature signals, is configured to control at least one of (a) the intensity of the optical radiation applied to the blanket 44 by one or more light sources, such as the source 111, and (b) the flow rate of the compressed air 101, or any other suitable gas, directed toward the surface 106 of the blanket 44.

[0168] In this example, the processor 20 and / or the controller 54 is configured to control the IR light intensity and the flow rate of the compressed air 101 based on a plurality of temperature signals received from a plurality of temperature sensors disposed along the blanket 44. As described above, the blanket 44 is typically cooled by the temperature of the surrounding environment. For example, the temperature of the ambient air and the roller 78 can be substantially lower than 100° C. (e.g., any temperature between about 25° C. and 100° C.).

[0169] In some embodiments, the utility dryer 97 and the lower dryer 75 of the system 110 can each include five drying units 222 that are arranged in a configuration similar to that of the main dryer 64 or that use any other suitable configuration. In one embodiment, the blanket preheater 98 can include a single drying unit 222, or one dryer 66, or one or more sources 111 without a device for flowing the compressed air 111.

[0170] In some embodiments, the structure of the drying unit 222 prevents the compressed air 101 entering from the AIC 122 from mixing with the compressed air 101 flowing into the surface 106 through the opening 195. As described above, after flowing through the opening 195, the compressed air 101 is forced to flow into the AOC 123 through the air outlet passage 130 disposed between adjacent units 222. In other words, after flowing through the opening 195, the compressed air, which may contain ink residues, does not mix with the incoming air flowing within the drying unit 222.

[0171] The configurations of the main dryer 64, the white dryer 97, the lower dryer 75, the drying unit 222, and the air outlet passage 130 are provided as an example. In other embodiments, at least one of these dryers and units may have any other suitable configuration. For example, instead of having a central AIC 122 and AOC 123 and using a valve (not shown) to control the flow rate of the compressed air 101, the system 10 and / or the system 110 may include a plurality of AICs 122 and / or AOCs 123 coupled to one or more of the aforementioned dryers.

[0172] Control of the Ink Drying Process FIG. 5 is a schematic illustration of a blanket 500 used in a digital printing system in accordance with an embodiment of the present invention. The blanket 500 may replace, for example, the blanket 44 of the systems 10 and 110 shown in FIGS. 1-4 above.

[0173] In some embodiments, the blanket 500 is moved in the direction of movement represented by the arrow 94, and includes a section 502 on which an ink image is printed and a section 506 disposed between adjacent sections 502 and that does not receive ink droplets from the aforementioned printing bars 61 and 62.

[0174] In some embodiments, the blanket 500 has a width 510 of about 1040 mm to 1050 mm, the section 502 has a length 504 of about 750 mm, and the section 506 has a length 508 of about 750 mm.

[0175] In some embodiments, the sources 111 are typically arranged along the width 510, and at least a portion of the sources 111 has a width of about 1120 mm that enables uniform heating along the entire width of the blanket 500. In such embodiments, the processor 20 and / or the controller 54 are configured to control the movement of the blanket 500 in the direction of the arrow 94 at a predefined speed (e.g., about 1.7 meters per second) that maintains uniform heating of the entire area of the blanket 500.

[0176] In some embodiments, the processor 20 and / or the controller 54 is configured to control the temperature sensors 92 (e.g., temperature sensors 92A-92E) to measure the temperature of the blanket 500 at a predetermined frequency, in this example, about every 20 milliseconds. In such embodiments, at a moving speed of 1.7 meters per second, each temperature sensor 92 measures the temperature of the blanket 500 at a frequency of about every 34 mm.

[0177] In some embodiments, the processor 20 and / or the controller 54 are each configured to receive temperature signals 554 and 555 indicative of the temperatures measured in sections 502 and 506 of the blanket 500 (e.g., by temperature sensors 92). As explained in FIG. 2 above, the blanket temperature is determined, inter alia, by the coverage level, which is the amount of ink applied to the blanket surface.

[0178] In the example of the blanket 500, the coverage level in section 502 can vary according to the pattern of the ink image, while section 506, which does not receive ink from the printing bars 61 and 62, is expected to have a uniform temperature. Note that due to the latent heat of the ink placed on section 502, at least a portion of the energy of the light beam 99 is absorbed by the ink, resulting in a lower effect for direct heating of the blanket 500.

[0179] In some embodiments, when the processor 20 and / or the controller 54 receives the temperature signals 554 and 555 from one or more of the temperature sensors 92 (e.g., selected from temperature sensors 92A-92E), the temperature measured in section 506 is typically higher than the temperature measured in section 502.

[0180] In some embodiments, the processor 20 and / or the controller 54 are configured to determine the highest temperature of the blanket 500 using any suitable analysis based on the temperature signals 554 and 555. For example, the processor 20 and / or the controller 54 may store a predetermined amount (e.g., about 100) of the most recent temperature signals 554 and 555. Thereafter, the processor 20 and / or the controller 54 may select the temperature signals indicating the top three highest temperatures from among the stored signals and determine the highest temperature of the blanket 500 by calculating the median of the top three highest temperatures.

[0181] In other embodiments, the processor 20 and / or the controller 54 may determine the highest temperature of the blanket 500 using any suitable analysis of the temperature signals 554 and 555.

[0182] In an alternative embodiment, the processor 20 and / or the controller 54 are configured to control one or more of the temperature sensors 92A - 92E to measure the temperature of the blanket 500 using any other suitable sampling frequency.

[0183] In some embodiments, based on the calculated highest temperature of the blanket 500, the processor 20 and / or the controller 54 are configured to control the intensity of the IR radiation emitted from the source 111 and the flow rate of the compressed air 101.

[0184] In such an embodiment, in response to the calculation of a highest temperature of about 140°C, the processor 20 and / or the controller 54 are configured to decrease the intensity of the light beam 99 and / or increase the flow rate of the compressed air 101.

[0185] In some embodiments, the processor 20 and / or the controller 54 are configured to calculate the temperature along different sections of the blanket 500 based on any suitable sampling amount of the temperature signals 554 and 555.

[0186] In some embodiments, the processor 20 and / or the controller 54 are configured to maintain the temperature of the blanket 500 by holding thresholds indicating the specified maximum and minimum temperatures of the printing process and controlling at least a portion of the aforementioned dryers (e.g., the main dryer 64 and the lower dryer 75).

[0187] For example, after the main dryer 64, in response to detecting and calculating a temperature level lower than the specified minimum temperature, the processor 20 and / or the controller 54 are configured to control the lower dryer 75 to increase the intensity of the light beam 99 and / or decrease the flow rate of the compressed air 101.

[0188] As described above, in addition to the flow rate of the compressed air 101, the blanket is typically cooled by the surrounding environment that physically contacts the blanket. For example, the temperature of the air (or other gas) surrounding the blanket and the temperature of the roller 78 can be significantly lower than 100 °C (e.g., any temperature between about 25 °C and 100 °C).

[0189] In some embodiments, the processor 20 can receive position signals indicating the position of each marker or other reference point of the blanket, as described in FIG. 1 above. Based on the position signals, the processor 20 and / or the controller 54 are configured to adjust the intensity of the light beam 99 and / or the flow rate of the compressed air 101 in one or more of the aforementioned dryers.

[0190] For example, when the blanket is moved within the system 10, the processor 20 can associate a first specific marker of the blanket 500 with the section 502 and a second specific marker of the blanket 500 with the section 506. In one embodiment, when a first specific marker passes very close to a given source 111 of the main dryer 64, the processor 20 can control the main dryer 64 to increase the intensity of the light beam 99 directed from the given source 111 to the blanket 500.

[0191] Similarly, when a second specific marker passes very close to a given source 111 of the main dryer 64, the processor 20 may control the main dryer 64 to reduce the intensity of the light beam 99 emitted from the given source 111.

[0192] In some embodiments, the processor 20 and / or the controller 54 are configured to set, for example, in the dryer 62, a constant intensity of the light beam 99 and a constant flow rate of the compressed air 101. In such embodiments, a first set of ink droplets placed at a given position on the blanket surface is partially dried, such that a second set of ink droplets later applied to that given position by other printing bars is mixed with the first set of ink droplets at the given position of the blanket to produce a specified mixed color.

[0193] In some embodiments, the processor 20 and / or the controller 54 are configured to control the temperature of the compressed air 101 applied to the blanket (e.g., blanket 44 or blanket 500). For example, a specified temperature of the compressed air 101 may be about 30°C. The systems 10 and 110 may operate in various countries and seasons with a wide range of ambient temperatures. For example, the ambient temperature can range from about 45°C in summer in warm countries to -30°C in winter in cold countries.

[0194] In some embodiments, at ambient temperatures below 30°C, the systems 10 and 110 are configured to filter ink by-products from the warm air extracted from the surface 106 of the blanket 44 by the AOC 123. In such embodiments, the processor 20 and / or the controller 54 are configured to control the AIC 122 to mix the filtered warm air with the ambient air in order to have air compressed at about 30°C and applied to the blanket 44.

[0195] In some embodiments, at an ambient temperature above 30°C, the processor 20 and / or the controller 54 controls the AIC 122 to mix the warm air of the environment with the air cooled by the printing plant (e.g., using an air conditioning system or any other technique) using the system 10 or 110 to have air of about 30°C, and is configured to compress the mixed air and apply it to the blanket 44.

[0196] In some embodiments, the systems 10 and 110 include a current sensor (not shown) coupled to an electrical cable (not shown) that supplies current to the source 111. The current sensor is configured to detect the inductance level on the electrical cable. In such embodiments, the processor 20 and / or the controller 54 is configured to receive from the current sensor a signal indicative of the current flowing through the electrical cable and to determine whether each source 111 is operating.

[0197] Blanket structure and process sequence for manufacturing a blanket adapted for IR-based drying of ink FIG. 6 is a schematic diagram generally showing a cross-sectional view of a process sequence for manufacturing a blanket 600 according to an embodiment of the present invention. The blanket 600 can replace, for example, the blanket 44 of either of the systems 10 and 110 and its features shown and described in FIGS. 1-5 above.

[0198] The process begins with the preparation of an exemplary stack of 6 layers including the blanket 600 on a carrier (not shown).

[0199] In some embodiments, the carrier can be formed from a flexible foil, such as a flexible foil including, for example, aluminum, nickel, and / or chromium. In one embodiment, the foil includes a sheet of polyethylene terephthalate (PET) coated with aluminum, also referred to herein as polyester, for example, PET coated with fumed aluminum metal.

[0200] In some embodiments, the carrier can be formed from an antistatic polymer film, such as a polyester film. The properties of the antistatic film can be obtained using various techniques, such as the addition of various additives, such as ammonium salts, to the polymer composition.

[0201] In some embodiments, the carrier has a polished plane (not shown) having a roughness (Ra) of about 50 nm or less, which is also referred to herein as the carrier contact surface.

[0202] In some embodiments, a first fluid-curable composition (not shown) is provided, from which the release layer 602 is formed on the carrier contact surface. In some embodiments, the release layer 602 includes an ink-receiving surface 612 configured to receive an ink image from, for example, an image-forming station 60 and transfer the ink image to a target substrate, such as the sheet 50, shown and described in FIG. 1 above. It should be noted that the layer 602, particularly the surface 612, is configured to have a low release force with respect to the ink image, measured by the wetting angle, which is also referred to herein as the receding contact angle (RCA), between the surface 612 and the ink image.

[0203] The low release force enables complete transfer of the ink image from the surface 612 to the sheet 50. In some embodiments, the release layer 602 can include a transparent silicone elastomer from vinyl-terminated polydimethylsiloxane (PDMS) or any other suitable type of silicone polymer and can have an exemplary thickness of about 10 μm to 15 μm, or any other suitable thickness greater than 10 μm.

[0204] In some embodiments, the first fluid-curable material includes a vinyl-functional silicone polymer, such as a vinyl silicone polymer including at least one lateral vinyl group in addition to terminal vinyl groups, such as vinyl-functional polydimethylsiloxane.

[0205] In some embodiments, the first fluid curable material may include a vinyl-terminated polydimethylsiloxane, a vinyl-functional polydimethylsiloxane containing at least one lateral vinyl group on the polysiloxane chain in addition to terminal vinyl groups, a crosslinking agent, and an addition-curing catalyst, and may optionally further include a cure retarder.

[0206] In the example of FIG. 6, the release layer 602 may be uniformly applied to a PET-based carrier flattened to a thickness of 5 to 200 μm and cured at 120 to 130° C. for about 2 to 10 minutes. Note that the hydrophobicity of the ink transfer surface 612 may have an RCA of about 60° with 0.5 to 5 microliters (μl) droplets of distilled water. In some embodiments, the surface of the release layer 602 (in contact with the surface 614 described below) may have a significantly high, typically about 90° RCA.

[0207] In some embodiments, the PET carrier used to produce the ink transfer surface 612 may have a typical RCA of 40° or less. All contact angle measurements were performed using a contact angle analyzer "Easy Drop" FM40Mk2 manufactured by Kruss (trademark) GmbH, Borsteler Chaussee 85, 22453 Hamburg, Germany and / or a Dataphysics OCA15 Pro manufactured by Particle and Surface Sciences Pty. Ltd., Gosford, NSW, Australia.

[0208] In some embodiments, the blanket 600 has an exemplary thickness in the range of about 30 μm to 150 μm and includes an IR layer 603 configured to absorb all or a significant portion of the IR radiation of the light beam 99. In this example, the IR layer 603 is adapted to absorb about 50% of the IR radiation of the light beam 99 within 5 μ of its upper portion. In other words, the IR layer 603 substantially does not pass the light beam 99.

[0209] Referring now to the insert view 611 showing a cross-sectional view of the IR layer 603. In some embodiments, the IR layer 603 is applied to the release layer 602 and has a surface 612 that joins therewith and a surface 618 that joins with a compliance layer 604 described in detail below.

[0210] In some embodiments, the IR layer 603 includes a matrix made of silicone (e.g., PDMS) and a plurality of particles 622 disposed at a given location within the bulk of the PDMS matrix of layer 603. In some embodiments, the particles 622 include any type of pigment, such as, but not limited to, commercially available carbon black (CB) particles, each of which has a typical diameter in the range between about 10 μm (relative to the thickness of the IR layer 603 of about 30 μm) and about 30 μm (relative to the thickness of the IR layer 603 of about 50 μm).

[0211] In some embodiments, the particles 622 are embedded within the bulk of the IR layer 603 within a distance 616 of about 10 μm or 20 μm from the surface 614. The particles 622 are also arranged uniformly along the layer 603 at a distance 617 of about 0.1 μm to 5 μm from each other. In other embodiments, the distances 616 and 617 can be varied between different blankets, for example, at least one particle can be in close proximity to or in contact with either the surface 614 or 618. Similarly, the distance 617 can vary along the IR layer 603.

[0212] In some embodiments, having the particles 622 embedded within the bulk of the IR layer 603 rather than at the surface 614 can improve the adhesion between the IR layer 603 and the release layer 602. Similarly, having the particles 622 embedded within the bulk of the IR layer 603 can improve the adhesion between the IR layer 603 and the compliance layer 604.

[0213] In some embodiments, after coating and curing the release composition on PET, an IR layer 603 having CB particles is coated on the cured release layer and also cured. The insertion of CB particles, or any other suitable type of particles, into the IR layer 603 can be carried out by mixing the particles into the matrix of the IR layer before applying the layer to the release layer, or by placing the particles after applying the IR layer to the release layer, or by using any other suitable technique. Thereafter, a PDMS layer is coated on the cured IR layer, a glass fiber layer is applied, and all the structures are cured. Finally, a silicone resin is coated on the glass fiber layer and cured.

[0214] In other embodiments, the CB particles and their location can affect the drying process of the ink applied to the surface 612 of the release layer 602, as will be described in detail below.

[0215] Now, referring back to the overview of the blanket 600. In some embodiments, the blanket 600 includes a compliance layer 604, typically made of PDMS and also referred to herein as a conformal layer, which may include a black pigment additive. The compliance layer 604 is applied to the IR layer 603 and may have a typical thickness of about 150 μm, or any other suitable thickness of about 100 μm or more.

[0216] In some embodiments, the compliance layer 604 can have mechanical properties (e.g., greater resistance to tension) that are different from, for example, both the release layer 602 and the IR layer 603. Such desired differences in properties can be obtained, for example, by utilizing different compositions with respect to the release layer 602 and / or the IR layer 603, by varying the properties between the components used to prepare the compositions of the release layer 602 and / or the IR layer 603, and / or by adding additional components to such compositions, and / or by selecting different curing conditions. For example, adding filler particles can increase the mechanical strength of the compliance layer 604 compared to the release layer 602 and / or the IR layer 603.

[0217] In some embodiments, the compliance layer 604 has elastic properties that allow the release layer 602 and the surface 612 to closely follow the surface contour of the substrate (e.g., sheet 50) onto which the ink image is applied. The attachment of the compliance layer 602 to the side opposite the ink transfer surface 612 may involve the addition of an adhesive or joining composition in addition to the material of the compliance layer 602.

[0218] In some embodiments, the blanket 600 is coated on the compliance layer 604 and includes a reinforcing stack layer, herein also referred to as the support layer 607 or the skeleton of the blanket 600, which is described in detail below. In some embodiments, the support layer 607 is configured to provide the blanket 600 with improved mechanical resistance to deformation or rupture that may be caused by the torque applied to the blanket 600, for example, by the rollers 78 and the dancer assembly 74. In some embodiments, the skeleton of the blanket 600 includes an adhesive layer 606 made of PDMS or any other suitable material, which is formed together with the glass fiber fabric layer 608. In some embodiments, the layers 606 and 608 may each have a typical thickness of about 150 μm and about 112 μm, or any other suitable thickness, so that the thickness of the support layer 607 is typically about 200 μm.

[0219] In other embodiments, the skeleton can be produced using any other suitable process, for example, by placing the layer 606 and then bonding and polymerizing the layer 608 thereto, or by using any other process sequence.

[0220] In some embodiments, the polymerization process may be based on a hydrosilylation reaction catalyzed by a platinum catalyst, which is commercially known as "addition curing".

[0221] In other embodiments, the skeleton of the blanket 600 may include any suitable fiber reinforcement in the form of a web or fabric to provide sufficient structural integrity to the blanket 600 to withstand elongation, for example, when tension is maintained within the system 10. The skeleton may be formed by coating the fiber reinforcement with any suitable resin that is later cured and remains flexible after curing.

[0222] In an alternative embodiment, the support layer 607 may be formed separately such that the fibers are embedded and / or impregnated within separately cured resin. In this embodiment, the support layer 607 may be attached to the compliance layer 604 via an adhesive layer, optionally eliminating the need to cure the support layer 607 in place. In this embodiment, the support layer 607 may have a thickness between about 100 μm and about 500 μm, whether formed in place or separately on the compliance layer 604, with a portion thereof due to the thickness of the fiber or fabric, which generally varies between about 50 μm and about 300 μm. It should be noted that the thickness of the support layer 607 is not limited to the foregoing values.

[0223] In some embodiments, the blanket 600 is typically made of transparent PDMS and includes a high friction layer 610, also referred to herein as a grip layer, configured to physically contact between the blanket 600 and the rollers and dancers of the systems 10 and 110 described in FIGS. 1 and 2 above, respectively. It should be noted that although the layer 610 is made of a relatively soft material, the surface facing the roller has high friction so that the blanket 600 can withstand the torque applied by the rollers and dancers without sliding. In an example embodiment, the layer 610 may have a thickness of about 100 μm, but alternatively may have any other suitable thickness, such as between 10 μm and 1 mm.

[0224] Additional embodiments implementing the generation of layers 602, 604, 606, 608, and 610 of blanket 600 are described in detail, for example, in PCT International Publication No. WO2017 / 208144, the disclosure of which is incorporated herein by reference.

[0225] Referring again to insertion figure 611, for example, as described in FIGS. 1, 3, and 4 above, the printing bar 62 of imaging station 60 applies ink droplets to the surface 106 of blanket 44. In the example of blanket 600 shown in FIG. 6, the printing bar 62 of imaging station 60 applies ink droplets to the surface 612 of release layer 602.

[0226] In some embodiments, the CB content of particles 622 is configured to absorb the IR radiation of light beam 99 passing through release layer 602. In response to the IR radiation of light beam 99, particles 622 are configured to have a temperature higher than the temperature of the silicone matrix of IR layer 603. In other words, the CB particles absorb the IR radiation and emit heat rays 620 and 621 across IR layer 603. In such embodiments, heat rays 620 and 621 are respectively raising the temperatures of layers 602 and 604.

[0227] In some embodiments, the silicone matrix of IR layer 603 has a low thermal conductivity, so that heat ray 620 travels within IR layer 603 to create a uniform temperature rise across IR layer 603 and release layer 602.

[0228] Additionally or alternatively, the CB particles may be embedded within release layer 602.

[0229] In some embodiments, having release layer 602 (which passes IR radiation) over IR layer 603 (configured to absorb IR radiation) is to trap heat rays 620 and 621 within blanket 600, thereby facilitating the drying process of the ink droplets applied to surface 612.

[0230] In such an embodiment, the heat generated by the heat ray 620 can be accumulated between the layers 602 and 603 and within the layers 602 and 603, and the low thermal conductivity of these layers allows the heat to be uniformly dispersed across the surface 612 of the blanket 600.

[0231] Based on the above description of the blanket 600, the total thickness between the particles 622 and the outer surface of the layer 610 is about 0.5 mm, while the distance between the particles 622 and the surface 612 is about 20 μm or 30 μm. As shown in FIG. 6, the heat ray 621 appears shorter than the heat ray 620 to show that most of the heat generated by the CB particles dissipates towards the surface 612. In such an embodiment, most of the heat generated by the CB particles is used to dry the ink droplets applied to the surface 612 of the blanket 600.

[0232] FIG. 7 is a flowchart schematically showing a method for manufacturing a blanket 600 according to an embodiment of the present invention. The method starts with a first layer generation step 700 of generating a release layer 602 formed on a PET-based carrier contact surface as described in FIG. 6 above. In some embodiments, the release layer 602 includes an ink receiving surface 612 configured to receive an ink image, for example, from an image forming station 60, and transfer the ink image to a target substrate such as a sheet 50, as shown and described in FIG. 1 above. In some embodiments, the release layer 602 is at least partially disposed on the outer surface of the blanket 600 through the light ray 99 of IR radiation, as shown and described in detail in FIG. 6 above.

[0233] In the second layer coating step 702, the IR layer 603 is applied to the release layer 602. In some embodiments, the IR layer 603 includes a matrix made of silicone (e.g., PDMS). The matrix holds a plurality of particles 622 (e.g., carbon black particles) that are arranged at a given position within the bulk of the PDMS matrix of layer 603 and are configured to absorb optical radiation (IR radiation of the light beam 99 in this example) to heat the release layer 602 and dry at least a portion of the ink droplets applied to the ink receiving surface 612. Although the method of FIG. 7 is completed at step 702, additional steps for manufacturing the blanket 600 are described in detail in FIG. 6 above.

[0234] FIG. 8 is a flow diagram schematically showing a method for drying ink and controlling the temperature of a blanket during a digital printing process according to an embodiment of the present invention.

[0235] In the context and claims of the present disclosure, the term "blanket" refers to the blanket 44 of FIGS. 1-4, the blanket 500 of FIG. 5, the blanket 600 of FIG. 6, and any other suitable type of ITM. Although embodiments of the method of FIG. 8 are described using the blanket 600, they are applicable to all of the aforementioned types of blankets and ITMs, as well as other suitable types of ITMs.

[0236] The method begins with an optical radiation directing step 800 that directs IR radiation, such as the light beam 99, onto the surface 612 of the release layer 602, which is configured to pass at least a portion of the optical radiation and (i) receive ink droplets, (ii) form an image thereon, and (iii) transfer that image to a target substrate, such as the sheet 50 or the web 51. In some embodiments, at least a portion of the IR radiation of the light beam 99 is absorbed by particles 622 (e.g., carbon black particles) arranged at a given position within the bulk of the PDMS matrix of layer 603.

[0237] In some embodiments, when absorbed by the particles 622, the IR radiation heats the release layer 602 to at least partially dry the ink droplets of the ink image formed on the surface of the release layer.

[0238] In the blanket temperature control step 802 that completes the method, the processor 20 controls the temperature control assembly to direct a gas (compressed air in this example) at a predetermined flow rate to control the temperature of the blanket to, for example, about 70 °C or 80 °C as described in FIGS. 1 and 2 above.

[0239] For example, as described in FIGS. 2 and 3 above, the dryer 66 has a blower and includes one or more openings to the AIC 122 configured to supply compressed air 101 (or any other suitable type of gas) to the dryer 66. In some embodiments, the dryer 66 further includes one or more openings to the AOC 123 having an air extraction device (e.g., a vacuum or negative pressure pump of a suitable type) configured to extract the compressed air 101 after cooling the blanket.

[0240] The embodiments described herein mainly address the drying of an intermediate transfer member in a digital printing system, and the methods and systems described herein can also be used in other applications, such as the drying of liquids from any substrate, or in other applications such as the heating or annealing or curing of any substrate, but are not limited thereto.

[0241] Accordingly, it will be understood that the foregoing embodiments are cited by way of example, and that the present invention is not limited to what has been specifically shown and described hereinabove. Rather, the scope of the present invention includes both the various combinations and subcombinations of the foregoing features, as well as variations and modifications thereof that are not disclosed in the prior art and would occur to one of ordinary skill in the art upon reading the foregoing description. Documents incorporated by reference in this patent application are to be considered an integral part of this application except that any terms defined in these incorporated documents in a manner that conflicts with any definition explicitly or implicitly made herein are excluded, and only the definitions in this specification should be considered.

Claims

1. A system comprising: A flexible intermediate transfer member (ITM), the ITM comprising at least (i) a first layer disposed on an outer surface of the ITM and configured to receive ink droplets from an ink supply subsystem and form an ink image thereon and transfer the ink image to a target substrate, and (ii) a second layer comprising a matrix that holds particles at respective given positions, the second layer being configured to receive optical radiation passing through the first layer, the particles being configured to heat the ITM by absorbing at least a portion of the optical radiation; an ITM; An illumination assembly configured to dry the ink droplets by directing the optical radiation to act on at least a portion of the particles, the particles being configured to be embedded within a bulk of the second layer at a given distance from the outer surface to uniformly heat the outer surface; A temperature control assembly configured to control the temperature of the ITM by directing a gas toward the ITM; A processor configured to receive a temperature signal indicative of the temperature of the ITM and, based on the temperature signal, control at least one of (i) the intensity of the optical radiation and (ii) the flow rate of the gas; A system.

2. The system of claim 1, wherein the first layer and the second layer are adjacent to each other and the particles are disposed at a predetermined distance from each other to uniformly heat the outer surface.

3. The system of claim 1 or 2, wherein the optical radiation comprises infrared (IR) radiation and at least one of the particles comprises carbon black (CB).

4. A method comprising: Directing optical radiation at a flexible intermediate transfer member (ITM), said ITM comprising at least (i) a first layer disposed on an outer surface thereof for receiving ink droplets and forming an ink image thereon and for transferring said ink image to a target substrate, and (ii) a second layer comprising a matrix holding particles disposed at respective given positions, said optical radiation passing through said first layer, said particles absorbing at least a portion of said optical radiation to heat said ITM, said optical radiation acting on at least a portion of said particles of said second layer to dry said ink droplets on said outer surface, and said particles being embedded within a bulk of said second layer at a given distance from said outer surface to uniformly heat said outer surface, receiving a temperature signal indicative of a temperature of said ITM, and controlling the temperature of said ITM by controlling at least one of (i) an intensity of said optical radiation and (ii) a flow rate of a gas directed at said ITM based on said temperature signal, A method comprising.

5. The method according to claim 4, wherein said first layer and said second layer are adjacent to each other, and said particles are disposed at a predetermined distance from each other to uniformly heat said outer surface.

6. The method according to claim 5, wherein directing said optical radiation comprises directing infrared (IR) radiation, and at least one of said particles comprises carbon black (CB).

7. A method for manufacturing a flexible intermediate transfer member (ITM), said method comprising: generating a first layer disposed on an outer surface of said ITM for receiving ink droplets and forming an ink image thereon and for transferring said ink image to a target substrate; coating said first layer with a second layer comprising a matrix holding particles disposed at respective given positions, said generating of said first layer comprising coating said first layer on a carrier and removing said carrier from said ITM at least after coating said second layer. A method comprising.

8. The method according to claim 7, wherein said particles are embedded within a bulk of said second layer at a given distance from said outer surface.

9. A system comprising A flexible intermediate transfer member (ITM) configured to receive ink droplets from an ink supply subsystem, form an ink image thereon, and transfer the ink image to a target substrate, wherein the ITM comprises particles at respective given positions, the ITM is configured to receive optical radiation, the particles are configured to heat the ITM by absorbing at least a portion of the optical radiation, and the particles are configured to be embedded within the bulk of the second layer at a given distance from the outer surface to uniformly heat the outer surface, the ITM; An illumination assembly configured to dry the ink droplets by directing the optical radiation to act on at least a portion of the particles; A temperature control assembly configured to control the temperature of the ITM by directing a gas towards the ITM; A processor configured to receive a temperature signal indicative of the temperature of the ITM and control at least one of (i) the intensity of the optical radiation and (ii) the flow rate of the gas based on the temperature signal; A system comprising. **Claim 10** The system of claim 9, wherein the optical radiation comprises infrared (IR) radiation and at least one of the particles comprises carbon black (CB).

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