Slot dies have heads that uniformly apply coatings to substrates. For providing coating with no defects, the die should be positioned in the ideal geometry between the substrate and die lips. This can be accomplished by following some techniques:
· Wipe/Contact- The phenomenon in which the material is applied directly to the substrate supported by a backup roll is called a direct coating. When the material is applied to a metering roll and then transferred to the substrate it is called an indirect coating. It can achieve lower coating thickness in replacement of the direct coating methods.
· Curtain- This coating allows the increase in speed of production. In this coating, the material is directly applied to the substrate from distance. The die is positioned above the substrate to allow the fluid to coat thin and fast.
· Tensioned Web Over slot die coating- Tensioned Web Over slot die coating is also called free span coating. Tensioned Web Over slot die coating apply the material directly to the substrate without the help of a backup roll. This method is used with solutions so that it can adhere to the substrate.
