ABSTRACT
The objective of this chapter is to review brie¤y the drying process, drying equipment, drying strategies, and web handling available for coated webs. Based on the substrate materials, coated webs can be divided into three types: (1) coated paper and paperboard; (2) coated plastic lms (e.g., photographic lms) and tapes (e.g., adhesive tapes, magnetic tapes, pressure-sensitive tapes, and photosensitive tapes); and (3) coated metallic sheets. Paper and paperboard are coated on machine or off machine, while plastic lms, tapes, or metallic sheets are generally coated off machine. (On machine indicates the coating operation that is done on the web before it is removed from the original manufacturing machine, whereas off machine implies the coating operations done on a free-standing machine remote from the original machine.)
During the coating process, some coated webs require a single coating; other webs require more than one coating layer either by passing a web of material through a single coating station more than one time or by coating a web with a multiple-station coating machine. In the converting industry, paper, lms, and foils can be combined together to form multiple-layer structures in a process called laminating. In the graphic arts industry, the coated papers are further coated
with ink to generate the desired images through a single printing station or multiple-color-printing units. Figure 46.1 shows a nished Polaroid instant color picture containing polyester supports on the top and bottom with active layers sensitized to the three primary colors (blue, green, and red), timing layers, and spacing layers to display the image between the supports.
