FOUNTAIN SOLUTION CONTACT ANGLE PINNING ON SECONDARY ROLLER
Ink-based digital printing systems useful for ink printing include a secondary roller having a rotatable reimageable surface layer configured to receive fountain solution. The fountain solution layer is patterned on the secondary roller and then partially transferred to an imaging blanket, where the fountain solution image is inked. The resulting ink image may be transferred to a print substrate. To achieve a very high-resolution (e.g., 1200-dpi, over 900-dpi) print with these secondary roller configurations, an equivalent very high-resolution fountain solution image needs to be transferred from the secondary roller onto the imaging blanket. To increase the resolution of the image on the secondary roller, examples include a textured surface layer added to the secondary roller for contact angle pinning the fountain solution on the roll. Approaches to introduce a micro-structure onto the surface layer of the secondary roller, and also superoleophobic surface coatings are described.
1 . A secondary roller useful for printing with an ink-based image forming device having a rotatable reimageable imaging member as the secondary roller and a rotatable inking blanket downstream the secondary roller and in rolling communication therebetween, the rotatable inking blanket configured to accept a patterned fountain solution latent image from the secondary roller and transfer an ink image based on the patterned fountain solution latent image, the secondary roller comprising a textured outer surface layer having a textured surface designed to reduce lateral spreading of fountain solution via fountain solution wetting between pixel areas of the outer surface.
2 . The secondary roller of claim 1 , wherein the textured surface is a pixeled surface having pixel sized lands surrounded by sharp edges between the lands.
3 . The secondary roller of claim 2 , wherein the sharp edges define indentations in the textured outer surface layer between the pixel sized lands.
4 . The secondary roller of claim 2 , wherein the sharp edges define a bump in the textured outer surface layer between the pixel sized lands.
5 . The secondary roller of claim 2 , wherein the pixel sized lands have low-surface energy coating between the sharp edges that decreases the surface energy of the textured surface.
6 . The secondary roller of claim 5 , wherein the bump is a ring-shaped bump that surrounds the pixel sized lands.
7 . The secondary roller of claim 1 , the textured surface including a low-surface energy coating that decreases the surface energy of the textured surface.
8 . The secondary roller of claim 7 , wherein the low-surface energy coating is an amorphous fluoropolymer.
9 . The secondary roller of claim 7 , wherein the textured surface is a pixeled surface having pixel sized lands thereon, the textured surface further comprising a bump between adjacent ones of the pixel sized lands.
10 . The secondary roller of claim 1 , wherein the textured surface includes a porous nanostructured omniphobic surface that decreases the surface energy of the textured surface.
11 . he secondary roller of claim 1 , wherein the textured surface includes a polycrystalline material having a high energy grain boundary.
12 . A method for reducing lateral spreading of fountain solution deposited on an outer surface of a secondary roller useful for printing with an ink-based image forming device having a rotatable reimageable imaging member as the secondary roller and a rotatable inking blanket downstream the secondary roller and in rolling communication therebetween, the rotatable inking blanket configured to accept a patterned fountain solution latent image from the secondary roller and transfer an ink image based on the patterned fountain solution latent image, the method comprising modifying the outer surface of the secondary roller into a textured outer surface layer having a textured surface designed for contact pinning of fountain solution between pixel land areas of the outer surface.
13 . The method of claim 12 , the modifying including surrounding the pixel sized lands with sharp edges between the lands.
14 . The method of claim 13 , the surrounding the pixel sized lands with sharp edges between the lands including inserting indentations in the textured outer surface layer between the pixel sized lands.
15 . The method of claim 13 , the surrounding the pixel sized lands with sharp edges between the lands including inserting surface bumps into the textured outer surface layer between the pixel sized lands.
16 . The method of claim 15 , further comprising adding a low-surface energy coating above the pixel sized lands between the sharp edges to decreases the surface energy of the textured surface.
17 . The method of claim 12 , further comprising modifying the outer surface of the secondary roller into a textured outer surface layer by adding a low-surface energy coating over the outer surface.
18 . The method of claim 12 , further comprising modifying the outer surface of the secondary roller into a textured outer surface layer by adding grain boundaries having polycrystalline with oleophobic and oleophilic grains over the outer surface.
19 . The method of claim 12 , further comprising modifying the outer surface of the secondary roller into a textured outer surface layer by one of microfabrication, lithography, embossing, sandblasting, laser ablation, polishing and bonding nano- and micro-particles to the outer surface.
20 . A secondary roller useful for printing with an ink-based image forming device having a rotatable reimageable imaging member as the secondary roller and a rotatable inking blanket downstream the secondary roller and in rolling communication therebetween, the rotatable inking blanket configured to accept a patterned fountain solution latent image from the secondary roller and transfer an ink image based on the patterned fountain solution latent image, the secondary roller comprising:
a textured outer surface layer having a textured surface designed to reduce lateral spreading of fountain solution via fountain solution wetting between pixel areas of the outer surface; and
a low-surface energy coating over the textured surface that decreases the surface energy of the textured surface,
wherein the textured surface is a pixeled surface having pixel sized lands surrounded by sharp edges between the lands.