Coating Process Technology
Machine-direction lanes: The simplest process to coat individual lanes is to tape the coating roll into segmented discrete lanes of the desired width. The open areas between lanes pick up the coating solution, and it is then transferred to the substrate as the discrete lanes. This process is acceptable for low-quality lanes and does not require new coating hardware.
The slot-die coater also coats machine-direction lanes by using internal inserts and deckles in the distribution cavity. The inserts restrict the coating-solution flow to the open area, which is then transferred to the substrate in the coating bead creating the machine-direction lanes. The slot-die process gives excellent quality, high-speed coating and a wide range of solution properties that could be coated.
Polygon patches: The initial technology to continuously coat discreet polygon patches was initiated by two patents issued in the 1990s. Choinski patented a process that created patches by flow control and mechanical movement of the extrusion-die coater to break the bead and create the discrete areas. The withdrawal time, return time, and deckles in the slot-die distribution plate determine the size of the patch.
Milbourn and Barth patented a sophisticated process using a slot-die coater in which the patch size was determined by precisely withdrawing the slot die to break the bead and the returning it to create patches. Subsequently, there has been ongoing development of commercial coaters to efficiently coat polygon patches. These are primarily based on the slot-die coater. A gravure coater also can be used to coat discrete area by engraving the required pattern on the gravure cylinder.