Emulsified curable oligomer-based inks for indirect printing method

#The present disclosure is generally related to indirect printing methods, and more specifically, to ink compositions for use in indirect printing methods.

#Indirect printing methods generally include a two-step printing process including applying ink imagewise onto an intermediate receiving member, such as a drum or a belt, using an inkjet printhead, and then transferring a transient image to a substrate. After the ink is applied imagewise onto the intermediate receiving member, the ink wets or spreads on the intermediate receiving member to form a transient image. The transient image undergoes a change in properties, such as partial or complete drying, thermal or photo-curing or gelation, and is then transferred to the substrate.

#Inks for use in an indirect printing method are designed and optimized to be compatible with the different subsystems, i.e., jetting and transferring. Specifically, an ink used in indirect printing must have properties, such as surface tension, viscosity, and particle size, suitable for use in a piezoelectric inkjet printhead. The ink must also be able to wet the intermediate receiving member to form the transient image and to undergo a stimulus induced property change to release from the intermediate receiving member in the transfer step.

#The FIGURE is a schematic representation of a two-step printing process.

#An aqueous inkjet ink comprising an emulsified curable oligomer has a number of advantages over inks that do not contain an emulsified curable oligomer. Using such an ink in a two-step printing process that includes applying the ink imagewise onto an intermediate receiving member and then transferring the ink from the intermediate receiving member to the substrate, results in an ink that displays both good wettability and good transferability while also providing a resulting image that is more robust than those resulting from inks that do not include an emulsified curable oligomer. After water is removed from the ink, the remaining curable oligomer may be exposed to radiation, such as UV light, and polymerized in the presence of a photoinitiator to form a robust final image. Printing to a transient substrate and removing the water before transfer to the final media reduces or removes negative effects on the final substrate, such as shrinkage and curl, that would be incurred if it was exposed to the high temperatures required for drying.

#As used herein, 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 in the context of a range, the modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the range “from about 2 to about 4” also discloses the range “from 2 to 4.”

#Indirect Printing