A method for ink-based digital printing includes applying a uniform layer of dampening fluid to a surface of an imaging member; laser patterning the dampening fluid layer by selectively removing portions of the dampening fluid according to digital image data; and inking the laser-patterned dampening fluid layer on the imaging member surface with a aqueous heterogeneous ink to form an ink image, wherein the aqueous heterogeneous ink self-coalesces before the ink is transferred from the imaging member surface.

An apparatus and method for printing directly onto print media including smooth non-absorbent media substrates (e.g., polymer films) inks having a wide range in viscosity, so that flexographic, gravure, and lithographic inks can all be contemplated. The proposed method is able to print with variable data/imaging. Dampening fluid may be patterned onto an imaging roll by coating the imaging roll with a layer of the dampening fluid and selectively evaporating off a patterned portion via a laser imaging device. The imaging roll then contacts the print substrate and transfers the patterned dampening fluid onto the substrate via film splitting. The substrate then passes through an inker station where ink is deposited directly to the substrate for attachment thereto except where rejected by the dampening fluid.

A variable lithographic inking system includes a chamber blade system configured to supply ink to an anilox member of an inking system. The inking system includes a soft ink transfer roll and a hard form roll. Ink is transferred from the anilox roll to the form roll by way of the transfer roll, and from the form roll to a reimageable surface layer of an imaging member of a variable data lithographic system. An ink layer free of ink history is uniformly applied onto a surface of the form roll, and subsequently transferred to the reimageable surface layer while avoiding or substantially eliminating image ghosting related to inking non-uniformities.

A heating circuit having an array of switching heating elements (e.g., field effect transistors, thin film transistors) provides a transient heat pattern over a surface (e.g., substrate, imaging member surface, transfer roll surface) moving relative to the heating circuit, to produce a pixelated heat image and heat a target pattern on the surface. Heat is generated by current flow in the heating elements, and the power developed by the heating circuit is the product of source-drain voltage and current in the channel. Digital addressing may accomplished by matrix addressing the array. Current may be supplied along data address lines by an external voltage controlled by digital electronics understood by a skilled artisan to provide the desired heat at a respective heating element pixels addressed by a specific gate line. The circuit may include a current return line that may be low resistance, for example, by using a 2-dimensional mesh.

A compliant surface is created with micron scale dimples above an electrically biased conductive layer. The dimpled surface is charged to a desired charge density and filled partially with fountain solution in either order. Then the compliant surface is brought adjacent a charge-retentive surface bearing an electrostatic charged pattern. In examples the fountain solution charge is repelled in the downward directed field under discharged (or uncharged) regions of the charge-retentive surface and is attracted to the surface at the electrostatic charged pattern in the regions of charged pixels. Electrostatic forces drag the fountain solution from the dimples to the charged pixel surface and away from the discharged pixel regions. Electrophoretic forces cause the fountain solution within the dimples to flow up to the charge image and wet the surface. A desired volume is controlled by varying parameters such as nip pressure.

According to aspects of the embodiments, there is provided a method of determining the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is determined from diagnostic images that are printed and analyzed using the existing Image Based Controls (IBC). An analysis of the density of solids, halftones, and background as a function of the fountain solution control parameter is performed to decide on the appropriate level of fountain solution. A latitude window of control parameters is then derived for which the digital offset lithography printing system in operation minimizes the undesirable effects of too much or too little fountain solution.

Examples of the preferred embodiments use printed content (e.g., halftones, difference in grayscale or darkness) to determine thickness of fountain solution applied by a fountain solution applicator on an imaging member surface and/or determine image forming device real-time image forming modifications for subsequent printings. For example, in real-time during the printing of a print job, a sensor may measure halftones or grayscale differences between printed content and non-printed content of a current printing on print substrate. Based on this measurement of printed content output from the image forming device, the image forming device may adjust image forming (e.g., fountain solution deposition flow rate, imaging member rotation speed) to reach or maintain a preferred fountain solution thickness on the imaging member surface for subsequent (e.g., next) printings of the print job.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured by using phase shifted monochromic light to produce optical path differences through the fountain solution film. The intensity of the reflected light through the fountain solution film is very sensitive due to the phase shifted light so interference fringes are easier to delineate and fountain solution thickness measurement more reliable.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a glass roll at a lower temperature than the fountain solution. The lower temperature causes the fountain solution to undergo a change in state and in a solid state the fountain solution crystalizes and changes roll opacity with the thickness of the film. When radiated with a light source the opacity is continuously measured through the surface of the roller. The thickness of the crystallized fountain solution can then be determined via the opacity level increase by the crystallization and the impact to the opacity on the glass roll.

According to aspects of the embodiments, there is provided a method of measuring the amount of fountain solution employed in a digital offset lithography printing system. Fountain solution thickness is measured using a diffractive optical element (DOE) configured with grating surfaces varying in a periodic fashion to hold an amount of fountain solution. When radiated with a light source the combination of the grating surface and the fountain solution therein reduces the scattering of the surface structure (“contrast”) that gives rise to a diffraction pattern. The diffractive optical element can be placed on the printing blanket of the lithography printing system or on a separate substrate.