Patent Grant
11820121
This invention relates generally to digital printing systems, and more particularly, to heat image forming systems and methods for selective thermal transfer useable in lithographic offset printing systems.
The application of heat is used in many technological situations, including image forming operations. Conventional digital imaging systems receive electronic image(s), which are passed to an image-processing unit. The image-processing unit may be a combination of software and hardware elements that accepts the electronic images from different sources and performs operations needed to convert the images to the format compatible with the output path of the digital reprographic system.
Conventional digital imaging systems may create images or printings using various types of image forming operations, including direct imaging processes such as elecrophotography, xerography, iconography, magnetography, ink jet technology, and thermal technology. In an exemplary digital imaging system, an aptly programmed hardware element, generally known as a raster image processor, converts the image in a page description language (PDL) or vector graphics format (VGF) to a bit mapped image indicating a value to print at each pixel of the image. Each bit representing a pixel that is “on” is converted to an electromagnetic pulse. The electromagnetic pulses generated from the raster pel data at which to deposit toner turns the laser beam on to positively charge the surface of a rotating drum that has a coating capable of holding an electrostatic charge. The laser beam turns on and off to beam charges at pixel areas on a scan line across the drum that will ultimately represent the output image. After the laser beam charges all pels on the scan line indicated in the raster data, the drum rotates so the laser beam can place charges on the next scan line. The drum with the electrostatic positive charges then passes over negatively charged toner. The negatively charged toner is then attracted to the positive charged areas of the drum that form the image. The print media, which is negatively charged, passes over the roller drum and attracts the toner as the areas of the roller drum with the toner are positively charged to transfer the toner forming the image from the roller drum to the print media.
Conventional digital imaging systems also include digital lithography imaging of variable image data for producing images on a substrate that are changeable with each subsequent rendering of an image on the substrate in an image forming process. For example, a digital offset printing process may include transferring ink onto a portion of an imaging member (e.g., fluorosilicone-containing imaging member, printing plate) having a surface or imaging blanket that has been selectively coated with a fountain solution (e.g., dampening fluid) layer according to variable image data. The fountain solution forms a film on the silicone plate that is on the order of about one (1) micron thick. The drum rotates to an ‘exposure’ station where a high power laser imager is used to remove the fountain solution at the locations where the image pixels are to be formed. This forms a fountain solution based ‘latent image’. The drum then further rotates to a ‘development’ station where lithographic-like ink is brought into contact with the fountain solution based ‘latent image’ and ink ‘develops’ onto the places where the laser has removed the fountain solution. The ink is usually hydrophobic for better adhesion on the plate and substrate. An ultra violet (UV) light may be applied so that photo-initiators in the ink may partially cure the ink to prepare it for high efficiency transfer to a print media such as paper. The drum then rotates to a transfer station where the ink is transferred to a printing medium such as paper. The silicone plate is compliant, so an offset blanket is not used to aid transfer. UV light may be applied to the paper with ink to fully cure the ink on the paper.
In some instances, the ability to form a transient heat pattern over a surface is useful to these imaging approaches. It would be beneficial to provide such transient heat patterns accurately and efficiently using reduced power consumption than conventional heaters and light sources.
The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments or examples of the present teachings. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description presented later. Additional goals and advantages will become more evident in the description of the figures, the detailed description of the disclosure, and the claims.
The foregoing and/or other aspects and utilities embodied in the present disclosure may be achieved by providing a heat image forming device for selectively heating an adjacent surface. The heat image forming device may include an array of switching heating elements and a plurality of conductive lines. Each switching heating element may include a field effect transistor, with the transistors each having a semiconductor layer, a gate electrode, a source electrode, a drain electrode and a dielectric layer deposited as thin-films onto a substrate, the gate electrode separated from the drain electrode and source electrode by the dielectric layer. The semiconductor layer has a current channel defined by a spatial gap between the source electrode and gate electrode, and an overlapping distance of the drain and source electrodes in the semiconductor layer. The plurality of conductive lines includes gate address lines, current supply data lines, and current return lines, with each one of the gate electrodes electronically coupled to one of the gate lines, each one of the source electrodes electronically coupled to one of the data lines, and each one of the drain electrodes electronically coupled to one of the current return lines. Each heating circuit has a current supplied via a connecting current supply data line in the current channel that is controlled by a voltage applied to the gate electrode via a connecting gate address line. In examples, the current channel is closer to the surface being heated than the current return lines.
According to aspects illustrated herein, an exemplary method for selectively heating an adjacent surface with a heat image forming device is discussed, wherein the adjacent surface includes a plurality of regions, with some of the regions including a patterned image on the surface or areas of the surface where the patterned image will be rendered. The method includes moving the patterned image of the adjacent surface and the array of switching heating elements relative to each other, selectively switching the heating elements proximal to the moving patterned image to a first state based on the patterned image, and heating the regions including the patterned image or areas of the surface where the patterned image will be rendered.
According to aspects described herein, a system for selectively heating an adjacent surface with the heat image forming device is discussed, wherein the adjacent surface includes a plurality of regions, with some of the regions including a patterned image on the surface or areas of the surface where the patterned image will be rendered. The system includes a processor and a memory, the memory storing instructions to cause the processor to perform moving the patterned image of the adjacent surface and the array of switching heating elements relative to each other, selectively switching the heating elements proximal to the moving patterned image to a first state based on the patterned image, and heating the regions including the patterned image or areas of the surface where the patterned image will be rendered.
Exemplary embodiments are described herein. It is envisioned, however, that any system that incorporates features of apparatus and systems described herein are encompassed by the scope and spirit of the exemplary embodiments.
Various exemplary embodiments of the disclosed apparatuses, mechanisms and methods will be described, in detail, with reference to the following drawings, in which like referenced numerals designate similar or identical elements, and:
Illustrative examples of the devices, systems, and methods disclosed herein are provided below. An embodiment of the devices, systems, and methods may include any one or more, and any combination of, the examples described below. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth below. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Accordingly, the exemplary embodiments are intended to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the apparatuses, mechanisms and methods as described herein.
We initially point out that description of well-known starting materials, processing techniques, components, equipment and other well-known details may merely be summarized or are omitted so as not to unnecessarily obscure the details of the present disclosure. Thus, where details are otherwise well known, we leave it to the application of the present disclosure to suggest or dictate choices relating to those details. The drawings depict various examples related to embodiments of illustrative methods, apparatus, and systems for inking from an inking member to the reimageable surface of a digital imaging member.
When referring to any numerical range of values herein, such ranges are understood to include each and every number and/or fraction between the stated range minimum and maximum. For example, a range of 0.5-6% would expressly include the endpoints 0.5% and 6%, plus all intermediate values of 0.6%, 0.7%, and 0.9%, all the way up to and including 5.95%, 5.97%, and 5.99%. The same applies to each other numerical property and/or elemental range set forth herein, unless the context clearly dictates otherwise.
The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (for example, it includes at least the degree of error associated with the measurement of the particular quantity). When used with a specific value, it should also be considered as disclosing that value. For example, the term “about 2” also discloses the value “2” and the range “from about 2 to about 4” also discloses the range “from 2 to 4.”
The term “controller” or “control system” is used herein generally to describe various apparatus such as a computing device relating to the operation of one or more device that directs or regulates a process or machine. A controller can be implemented in numerous ways (e.g., such as with dedicated hardware) to perform various functions discussed herein. A “processor” is one example of a controller which employs one or more microprocessors that may be programmed using software (e.g., microcode) to perform various functions discussed herein. A controller may be implemented with or without employing a processor, and also may be implemented as a combination of dedicated hardware to perform some functions and a processor (e.g., one or more programmed microprocessors and associated circuitry) to perform other functions. Examples of controller components that may be employed in various embodiments of the present disclosure include, but are not limited to, conventional microprocessors, application specific integrated circuits (ASICs), and field-programmable gate arrays (FPGAs).
The terms “media”, “print media”, “print substrate” and “print sheet” generally refers to a usually flexible physical sheet of paper, polymer, Mylar material, plastic, or other suitable physical print media substrate, sheets, webs, etc., for images, whether precut or web fed. The listed terms “media”, “print media”, “print substrate” and “print sheet” may also include woven fabrics, non-woven fabrics, metal films, and foils, as readily understood by a skilled artisan.
The term “image forming device”, “printing device” or “printing system” as used herein may refer to a digital copier or printer, scanner, image printing machine, xerographic device, electrostatographic device, digital production press, document processing system, image reproduction machine, bookmaking machine, facsimile machine, multi-function machine, or generally an apparatus useful in performing a print process or the like and can include several marking engines, feed mechanism, scanning assembly as well as other print media processing units, such as paper feeders, finishers, and the like. A “printing system” may handle sheets, webs, substrates, and the like. A printing system can place marks on any surface, and the like, and is any machine that reads marks on input sheets; or any combination of such machines.
The term “fountain solution” or “dampening fluid” refers to dampening fluid that may coat or cover a surface of a structure (e.g., imaging member, transfer roll) of an image forming device to affect connection of a marking material (e.g., ink, pigmented toner, pigmented or dyed particles or fluid) to the surface. The fountain solution may include water optionally with small amounts of additives (e.g., isopropyl alcohol, ethanol) added to reduce surface tension as well as to lower evaporation energy necessary to support subsequent laser patterning. Low surface energy solvents, for example volatile silicone oils, can also serve as fountain solutions. The fountain solution may be non-aqueous including, for example, silicone fluids (such as D3, D4, D5, OS10, OS20, OS30 and the like), Isopar fluids, and polyfluorinated ether or fluorinated silicone fluid.
In examples, an approach for providing a transient heat pattern over a surface (e.g., substrate, imaging member surface, transfer roll surface) where in operation a pixelated heat image is produced by heating circuits. In aspects of the approach, a heating circuit having an array of switching heating elements (e.g., field effect transistors (FETs), thin film transistors (TFTs) is discussed. Heat is generated by current flow in the heating circuit, and the power developed by the heating circuit is the product of the source-drain voltage and the current in the channel, which is proportional to the effective carrier mobility. Digital addressing may be accomplished by matrix addressing the array, for example, with orthogonal gate and data address lines. Current may be supplied along the data lines by an external voltage controlled by known digital electronics to provide the desired heat at a respective pixel addressed by a specific gate line. The circuit may include a current return line that can be made low resistance, for example, by using a 2-dimensional mesh.
Benefits include the ability to heat at pixel-sized areas in an addressable fashion so that circuit heating might be used at least in the architecture discussed herein. The design of the heating elements and addressing circuitry may be used in different applications including over an inking blanket. Examples include curing a material in a pattern, localized phase change of a material, image-wise evaporation of a liquid material, patterned chemical reactivity, and a spatially moving heat scan pattern. Exemplary designs are described in which the array is close to the object being heated. Such a heat image forming device may include an array of heating elements that are switchable, digitally addressable, close to the surface, with high area coverage of the heating elements, and scalable in pixel size and array size. The heating elements may each have a separate small transistor, meaning the amount of charge needed to control it is also small. This allows for very fast re-drawing of the switchable heating elements to match an adjacent pattern to be heated, even when the heating elements and adjacent pattern move relative to each other.
Heat may be generated by current flow in the TFT 16 and the power developed by the TFT is understood as the product of the source-drain voltage and the current in the channel, which is proportional to the effective carrier mobility. Digital addressing may be accomplished by matrix addressing (e.g., active, passive) the array 12 with orthogonal gate address lines 18 electronically coupled to gate electrodes and with current supply data lines 20 electronically coupled to source electrodes, for example, as shown in
The circuit may require current return lines 22 shown in
The heat image forming device 10 may also include data line drivers 28 and gate line drivers 30. The gate line drivers 30 (e.g., power amplifier) may accept a low-power input from a power source and produce a high-current drive input for the gate address lines 18. The data line drivers 28 provide timing signals to switch the heating elements 14 as desired by matrix addressing to provide a transient pixelated heat pattern over a surface as well understood by a skilled artisan. The transient pixelated heat pattern may match a pattern (e.g., patterned image, digitally patterned image, predetermined pattern) of material on the adjacent surface to be heated, and may change as the adjacent surface moves to continually match the pattern of material. Data line drivers 28 may be coupled to the current supply data lines 20 on one or both ends of the array.
While not being limited by a particular theory, different FET technologies may be used depending on temperature and power requirements of the heating elements 14. Temperature limits for heating may be set in accordance with materials used to fabricate the TFTs 16 and power may be set or adjusted due in part by the TFT mobility, since high mobility corresponds to high current and therefore high power. The maximum source-drain and gate voltages also limit the power that can be developed and depend on the specific TFT, as well understood by a skilled artisan. Examples of TFT materials include polysilicon (e.g., LTPS), oxide semiconductors (e.g., InGaZnO (IGZO)), and amorphous silicon. LTPS polysilicon may be fabricated by laser recrystallization of a deposited silicon film. LTPS has a typical electron mobility of about 150-200 cm2/Vs and hole mobility of about 50-100 cm2/Vs. LTPS has a temperature limit of about 350° C. and can be fabricated on glass, quartz or polyimide. Oxide semiconductors have a general mobility of about 40-50 cm2/Vs and maximum temperature of about 300-400° C. These materials are typically sputtered but may also be deposited from solution and annealed. Amorphous silicon has a general mobility of about 0.5 cm2/Vs and maximum temperature of about 250° C. A-Si is typically deposited by plasma enhanced chemical vapor deposition.
The above materials may be produced on rigid or flexible substrates and capable of large area arrays. Matrix addressing is a known technique and the driver electronics are known as well understood by a skilled artisan. These arrays 12 are capable of pixel size down to about 50 μm and are fabricated in large areas up to about 3×3 m. Other TFT materials that are demonstrated but not in volume manufacturing include carbon nanotubes and organic semiconductors. Carbon nanotubes have a general mobility of about 50-80 cm2/Vs and a temperature limit of over 500° C. Organic semiconductors have a general mobility of about 1-5 cm2/Vs and a temperature limit of about 200° C.
The process carried out by the heat image forming device 10 to provide a transient pixelated heat pattern over a surface in an addressable fashion may be sequenced and controlled using one or more controllers 60. The controller 60 may read and execute heat instructions generated by an outboard computer (not depicted) based on a pattern of a material or object that is to be heated. For example, the array 12 of heating elements 14 may be selectively operated by matrix addressing as discussed herein based on input from the controllers. While the controller 60 is shown in communication with the heat image forming device 10, it is understood that the controller may be in communication with any component of a system or device associated with the heat image forming device, including the surface to be heated.
Thus operation and control of the heat image forming device 10 and adjacent surface to be heated may be performed with the aid of the controller 60, which is implemented with general or specialized programmable processors 62 that execute programmed instructions. The controller is operatively connected to memory 64 that stores instruction code containing instructions required to perform the programmed functions. The controller 60 executes program instructions stored in the memory 64 to form heated patterns on the surface to be heated (e.g., surface object 46 (
The heating element 14 shown in the figures is an electronic switch heater, having the current between source electrode 36 and drain electrode 38 controlled (or modulated) by the voltage applied to the gate electrode 32, which is separated from the drain and source electrodes by the highly insulating gate dielectric layer 34. The current flows in the plane of the semiconductor 40, perpendicularly to the applied gate voltage. Bottom gate heating elements 14 are not limited to this configuration, as for example, the source-drain electrodes 36, 38 may be underneath the semiconductor 40 rather than on top.
Heat may be developed in the current channel 44, which is near the top surface of the heating element 14 and adjacent a surface object 46 to be heated. In fact, in specific examples the current channel 44 may be closer to the surface object 46 than the current return lines 22, the data lines 20 and the gate lines 18. A passivation layer 48 may be deposited above the semiconductor layer 40 and on top of the current channel 44 to protect the source-drain contacts and the current channel. The passivation layer 48 may be an insulator such as silicon oxide. The current channel 44 may be less than about 200 nm or only about 10-100 nm thick. A surface layer 50 may be added and provide a specific contact material to the object 46 being heated. In examples, the surface layer 50 may be a patterned pad made of a high thermal conductivity material (e.g., a metal) to ensure a uniform temperature across the heating element 14 pixel. The passivation layer 48 and the surface layer 50 may be very thin (e.g., less than 250 nm, less than 150 nm, about 15-150 nm thick) so that the current channel heat source is very close to the object 46 being heated.
Still referring to
The example depicted in
Polysilicon may be used in a heater array because of its high mobility and hence high heating power. However, the LTPS array is fabricated as a top gate TFT largely because the process starts with the laser crystallization of a thin silicon film on a substrate to form the channel. In the top gate geometry, the heat source which is the TFT channel is necessarily separated from the top surface by a significant thickness of material because of the presence of the gate dielectric, the source-drain contacts and the mesh metal return. This combination of layers might be 2 or more microns thick. The thickness might be suitable for some applications but a thinner separation between the TFT channel heater element and the surface is desirable for applications requiring faster or more efficient heating.
As can be seen in
As noted above regarding the structure of the exemplary inverted top heating element 14 depicted in
The heater current is transmitted along the data lines 20 to respective heater elements 14. For a large heater array 12 with many field effect transistor pixels, the data lines 20 may be long and narrow (e.g., less than a third the pixel width by over 1000 pixels long, about 2-10 μm and extending over 1000 pixels). Thin film array fabrication may limit the metal thickness of the data lines 20 such that the smallest line resistance may be about 0.1 ohm/sq. An effect of these conditions may be to introduce a significant voltage drop (e.g., about 25%, more than about 20%) along the data line so that heater elements 14 distal the voltage source will pass a lower current than heater elements proximal to the voltage source, such that heating may be non-uniform across the length of the array 12. To prevent significant non-uniform heating, the voltage drop along the data line should be minimal, for example, less than about 5% or no more than about 1V out of an applied 20V supply. There are various ways that can be used individually or in combination to solve this problem of excessive voltage drop. For example, connecting data line drivers 28 to opposite ends of the data lines 20 reduces voltage drop. In addition, a large voltage drop (e.g., about 5V out of a 20V supply) may be compensated by the controller 60 controlling the data drivers 28 to increase the applied voltage at the locations where voltage drop is larger. Another exemplary approach is to vary the heating element 14 or TFT 16 design, for example the width-to-length ratio W/L, across the array 12 so that a lower voltage in the center of the array produces the same power and heat from center heating elements as edge heating elements receiving a higher voltage at the edge of the array.
The current return lines 22 also have a resistive voltage drop. However, the current return mesh 24 minimizes resistance when formed as a 2-dimensional metal grid as shown by example in
It is understood that the heating element TFTs 16 can be constructed in diverse ways, with a difference among these structures being the position of the electrodes 32, 36, 38 relative to the active semiconductor 40. For example, the top gate TFT depicted in
The disclosed embodiments may include an exemplary method for selectively heating an adjacent surface with the heat image forming device 10.
At Step S210, a surface of a conventional digital imaging system adjacent an array of switching heating elements move respective to each other across the array. In other words, the surface may move and/or the array may move such that the surface and array move relative to each other. The surface may have a patterned image on the surface or regions thereon where a patterned image will be rendered. The patterned image may be a material (e.g., ink, fountain solution, toner, surfactants, particulates), electromagnetic property (e.g., positive charge, negative charge) or state (e.g., solid, fluid) that may be affected by heating, as well understood to a skilled artisan. Operation of the method proceeds to Step S220, where during the moving, a controller selectively switches the heating elements to a heating on state to heat the regions including the patterned image or areas of the surface where the patterned image will be rendered. The heating elements may be selectively switched via active matrix addressing. Operation may cease at Step S220, or may continue by repeating back to Step S210, for continued movement and patterned heating of the surface adjacent the array of switching heating elements.
The exemplary depicted sequence of executable method steps represents one example of a corresponding sequence of acts for implementing the functions described in the steps. The exemplary depicted steps may be executed in any reasonable order to carry into effect the objectives of the disclosed embodiments. No particular order to the disclosed steps of the method is necessarily implied by the depiction in
Those skilled in the art will appreciate that other embodiments of the disclosed subject matter may be practiced with many types of image forming elements common to offset inking system in many different configurations. For example, although digital lithographic systems and methods are shown in the discussed embodiments, the examples may apply to analog image forming systems and methods, including analog offset inking systems and methods. It should be understood that these are non-limiting examples of the variations that may be undertaken according to the disclosed schemes. In other words, no particular limiting configuration is to be implied from the above description and the accompanying drawings.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also, various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.
This application claims the benefit under 35 U.S.C. § 119(e) of Application Ser. No. 63/139,181 filed on filed on Jan. 19, 2021 entitled NEXT GENERATION FOUNTAIN SOLUTION IMAGE FORMATION AND TRANSFER and whose entire disclosure is incorporated by reference herein.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5109240 | Engl | Apr 1992 | A |
| Number | Date | Country | |
|---|---|---|---|
| 20220227142 A1 | Jul 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| 63139181 | Jan 2021 | US |
