Patent Application
20110111134
The present invention is generally related to production of films, and more particularly related to production of films by printing.
Application of fluids and conversion to solid films using processes such as drying by heat, or by physical transformations such as structural changes due to fusion, and chemical transformations such as polymerization or photo-thermal decomposition using radiation, is used in many coatings such as painting, electronics manufacture, printing, deposition by thermo-chemical change (e.g. MOVCD), and protective paints, and coatings. A particularly powerful and fast emerging technology is digital printing. The large scale digital printing is done by application of fluid in precise drops using piezo, thermal inkjet devices and liquid electro photography (LEP). In conventional presses, fluids are applied using offset, gravure, screen, flexographic, and dry toner electro photography (EP). Special inks that can be thermally converted to films with electronics properties are used in preparing conductors, or semiconductors as in case of MOVCD. These technologies are used for film deposition, printing, and manufacture of articles such as PCBs or printed electronics devices such as RFID, solar panels and displays. For example, a system used by FUJI/XEROX describes high power xenon lamps used in fusion of toners. The film formation is caused by energy, either by direct bulk or blackout heating of the chambers and towers, or by a complete swath of radiation across the media, heating major portions of the film and substrates.
Example embodiments of the present disclosure provide systems and methods of energy on demand processing of films. Briefly described, in architecture, one example embodiment of the system among others can be implemented as follows: a printing device configured to deposit film precursor in a pattern on a substrate, the film precursor having high absorbance for at least one band of radiation; and an irradiation device configured to deliver energy to the film precursor in at least one band of radiation.
Embodiments of the present disclosure can also be viewed as providing methods of energy on demand processing of films. In this regard, one embodiment in such a method, among others, can be broadly summarized by the following: depositing film precursor in a pattern, the film precursor having high absorbance for at least one band of radiation; and delivering radiation energy to the film precursor in the at least one band of radiation.
The invention is described in reference to several drawings to illustrate the embodiments.
Embodiments of the present disclosure will be described more fully hereinafter with reference to the accompanying drawings in which like numerals represent like elements throughout the several figures, and in which example embodiments are shared. Embodiments of the claims may, however, be embodied in many different forms and should not be construed to be limited to the embodiments set forth herein. The examples set forth herein are non-limiting examples, and are merely examples among other possible examples. The term matched band is defined as the match between the absorption band of the precursors or films, and the emission band of the radiation source; which may have less than 100 nm difference in the wave lengths at full-width, half max band of absorption and emission spectrum.
There are examples of blackout pattern energy delivery (as in case of IR or xenon lamp) delivery, and there are examples of digital delivery of energy registering a pattern on a “full-bleed” black out of films (such as photolithography of circuits, and direct to plate processes). Extremely fast, precise and controlled deposition of films in the digital delivery methods in all methods described so far is followed by analog delivery of energy for drying, curing or setting the film precursors. There is a need for a very fast and high energy density delivery mechanism to the film precursors that are deposited by these techniques or printing methods. The energy in all methods described so far is delivered with primitive concept of “clothes line drying,” using radiation or ‘hot air currents.’ For example, the energy may be delivered to an entire surface under exposure, and in many cases the entire chamber using lamps and hot air currents, regardless of the fact that the film is only 1/100th to 1/10th of the mass requiring heating. Furthermore, the typical average coverage area in any printing is 50% of the total surface area. The energy needs for film formation processes (drying, fusing etc.) in modern devices is greater than 50% of the total energy required. With the acute environmental, energy and cost concerns, there is a severe unmet need to address the energy consumption. Table 1 provides example energy requirements of some digital presses.
There have been attempts to reduce energy used in fusing or drying. For example, Xerox engineers have developed a flash fusion using high powered xenon lamps, which is an analog process. As another example, MEGTEC has developed regenerative oxidizer dryers, that burn the ink/toner solvents used in printing to gain heat for drying. However, this is analog use of energy that does burn fuel, is costly and produces CO2. Apart from the energy costs, these systems suffer from other disadvantages. For example, inefficient delivery also requires long paths or tray delays and media deformation. The speed of drying also affects dot gain and ink mixing. Uncontrolled mixing of inks degrades print quality. This can be a major issue in the case of non-adsorbent media such as polymers, and lower quality media such as newsprint. Even in cases of adsorbent media, deposition of large quantity of ink may cause defects due to media deformation, image distortion due to mixing of inks at the borders (unintended bleeding of one color in other), and loss of dot definition due to excessive or too little spreading. In the case of dry toner electro photography (EP) or liquid electro photography (LEP), the fusing and drying speed may limit the printing speed, since the excessive energy application using current technologies can cause paper charring, and toner burns etc.
The systems and methods of energy on demand processing of films described herein provide an efficient form of delivery referred to as “Energy on Demand.” This disruptive process “specifically” delivers radiation energy “beam” to locations of films. In an example embodiment, only specific locations of the medium are covered by the film precursors. The film precursors have high absorption for a selected radiation band. “Specifically” delivered radiation energy may include any process where the deposition includes placing a high absorbance film precursor in a location, and at least the area location is exposed to energy by a raster controlled signal e.g. a pulse. This may be accomplished by activating a radiation source such as a high power LED, LASER diode or lamp focused on a small location defined by elements of the film covered area, such as by a bitmap.
In one example embodiment, the radiation source may be activated by an electronic signal synchronized with or in correlation to the electronic signal used to apply the film element, or a bitmap thereof. For example, the raster signal used to write a latent image of the print pattern in EP or LEP may be used to activate a radiation source to deliver energy to the area covered by toner on the media. In inkjet printing, the signals to nozzles or pens are used to activate the energy. In the case of lithography and offset printing, the digital images of images used to create lithographic plate are used to drive the energy delivery. In a functional system, the synchronized energy signal may have an optional time (td) delay in proportion to the travel time of the media from the application point to exposure point given by equation td=(d/s) where d=distance between application dot and energy and s=speed of the media.
In block 120, the film precursors are treated with an image-wise burst of radiation energy, a delivery of energy, in which the exposed areas are restricted to the area covered by the film precursors. In block 130, an alternative embodiment where the deposition process involves ‘flight’ of material from one location to another such as inkjet, MEMjet, dry toner EP and LEP, the particles travel through the energy beam of controlled intensity. The intensity of the beam may be adjusted according to the energy requirement of each of the materials and the effects thereof. A non-limiting example of delivery of energy may include implementing raster graphics or bitmap images to drive a beam reflected off a rotating mirror across the substrate, only exposing the electronic data deposited precursors to form a film. In an example embodiment using dry toner and LEP, the image files to drive the latent image on OPC may be used to synchronously drive an energy beam emanating from a source such as a LASER diode with appropriate delay introduced to allow for media travel. In an alternative embodiment a “process energy print bar” including an array of energy sources such as non-limiting examples of LEDs, LASER diodes, XENON lamps, and optical fiber arrays may be positioned across the path of media, and are activated by a latent image stored in the print driver memory.
In cases where the inkjet “print head” is scanned across the media to deposit films, the same signals used to fire the nozzles may be used to fire energy bursts from an attached LASER diode, or optical fiber attached to the body of the print head, with an added time delay for exact match of droplet and energy delivery. In case of the practice of the disclosed systems and methods of energy on demand processing of films where heating is the mechanism for film setting, the film precursors may absorb at least 20% of the radiation energy. In an example embodiment, the film precursors are configured to absorb 50% of the radiant energy. In an alternative embodiment, the film precursors may be configured to absorb 80% or more of the energy delivered by the source. For these configurations, the film precursors are have at least one absorption band that is matched to at least one band of the emission source and absorbs at least 50% of the radiation or Optical Density of 0.5 in precursor form. A matched band may have less than 100 nm difference in the wave lengths at full-width, half max band of absorption and emission spectrum.
In some cases of non-contact printing methods, the disclosed systems and methods of energy on demand processing of films may be applied in two stage “in-flight” and “on surface” exposure to control not only drying or fusing, but the dot gain, optical density and solvent composition of the material applied to the substrate. Ink jet and liquid electro photography are examples of such cases.
Various high speed commercial applications such as printing require that the absorbance requirements of the substrate do not affect the visual appearance of the ink films. In such cases, the maximum absorption band matched to source may be outside of visual absorption bands in the precursors. In case of the film precursors where drying occurs by polymerization such as UV inks, the absorption may be greatly reduced to at least 1%, more preferred 10% and most preferred >20% of the incident radiation. Due to recent advances in LED, LASER LED and lamp technologies, light sources in narrow wavelength band with high power density are available. The precursor or film absorbance parameters may be met due to intrinsic intended absorbance of the precursors or films, e.g. in case of printing inks For example, an ink with intense yellow color of optical density 1 absorbs 90% of blue waveband 400˜450 nm, an ink with magenta color of optical density 1 absorbs 90% of green waveband at 520˜620 nm, and the cyan color ink with optical density of 1 absorbs 90% of the red wave band at 640˜740 nm. In example embodiments, additives such as absorbers in UV, IR, and near-IR range may be added to the film to increase the absorbance in the selected regions matching with the radiation source.
Table 2 shows the film application/printing methods and the energy on demand options. A large number of architectures may be created using the combinations, although the table will result in 119 non-limiting example combinations of deposition and EOD engines.
A large number of commercially available light sources may be used in practice of the disclosed systems and methods of energy on demand processing of films, e.g. fibers, bars, component LEDs. Table 3 shows a list of light sources in UV/VIS and NIR ranges as non-limiting examples. Table 3 shows a list of example light sources.
The disclosed systems and methods of energy on demand processing of films offers greatly reduced energy costs, along with additional control parameters for print quality and media flexibility. Applications of this technology to a vast application such as printing may contribute to the green revolution.
In a non-limiting example, high absorbance cyan ink are produced by addition of 0.5% indo-cyanine green to commercially available Epson cyan ink compatible with Espon Artisan 50 inkjet printer. The ink provides unaltered cyan color in human visual observation, and intense absorption peak at 780 nm band, which is invisible to humans.
In another example embodiment, a high absorbance magenta ink is produced by addition of 0.5% indo-cyanine green to commercially available Epson magenta ink compatible with Artisan 50 Ink Jet printer. The ink shows unaltered magenta color in human visual observation, and shows intense absorption peaks at the 780 nm band, which is invisible to humans.
In another example embodiment, an EOD system using commercially available Artisan 50 as an inkjet platform was built. A a non-limiting example of a commercially available Epson Artisan printer was modified by mounting, a LASER such as a non-limiting example of a Northrup-Grumman (Minnesota) 40 W 780 nm laser fitted with a cooling assembly and control integrated circuits, receiving signals from a computer and delivering the signals to the LASER and print cartridges. Inks as prepared in previous examples may be loaded in the ink cartridges, and the print mechanism may be activated with or without the laser. Prints of bars were deposited on HP glossy photo paper. The extent of the drying of inks may be determined by positioning HP inkjet color lock paper over the films and running a pressure roller at 1 and 2 seconds after the film has exited the printer. Table 4 shows results of the experiment with commercial and EOD inks, with both laser on and laser off.
Inks with high absorbance and LASER ON dry significantly faster due to significantly higher energy absorption.
Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made thereto without departing from the spirit and scope of the invention as defined by the appended claims.
This application claims benefit of U.S. Provisional Application No. 61/259,538, entitled, Energy on Demand Processing Systems and Films Formed Thereof, filed Nov. 9, 2009, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61259538 | Nov 2009 | US |
