Patterning materials over large areas on flexible plastic or metal substrates, and on rigid ones, where multiple layers of different materials are being applied in order to create active devices brings with it the real challenge of accurate materials placement [1]. The additive process of printing expensive functional materials reduces costs associated with the losses of subtractive processing, but focuses the technological necessity on the precision of materials alignments on the target substrates. During the past decade, both materials and their print processing have developed to a near commercial level for optical and electronic devices. Industrial success will be assured when their production enjoys the economies of scale that large area processing can bring. Ink jet technology has developed in the last twenty-five years to a level of sophistication that is now adequate for the challenges of processing large area substrates for optical and electronic devices. Some equipment and processing will be covered in this paper.