• Film Quality - One of the primary benefits of Orthogonal Processing is the high quality of the films after patterning. Spin-coated or slot die coated films are typically of very high quality compared to printed films of the same material. The reason for this is that the materials can be formulated, and the solvents chosen, with performance in mind. Printed inks must be formulated to have the correct rheological factors so that they don't clog the printhead (in the case of inkjet printing), form flat, uniform features, and can form fine features on a particular surface. A common non-uniformity, called the coffee-ring effect, is due to the uneven way the solvent dries after printing and can cause performance issues such as lower mobility or conductivity in the final devices. A common fix for this problem is to define a wetting layer using SAMs or lithographically defined polymers. This method introduces unnecessary complication to the process without eliminating a lithography step. With the Orthogonal Process, a wide range of organic thin films can be patterned subtractively, leaving a perfectly uniform, high performance film, without any reformulation of the organic film.

• Resolution - Photolithography is capable of high resolution patterning on a variety of substrate materials. We have demonstrated Orthogonal resist patterning of half a micron on an i-line lithography tool as well as 2 µm on PET films. While these resolutions may be more than is required for most OE devices, it is good to know that critical dimensions are well under control and are not the source of yield problems.

• Registration - A big advantage of the Orthogonal process is that it takes advantage of the high degree of accuracy of modern photolithography systems. Overlays well below 1 µm are routinely achievable, and this can enable more complex devices with multiple functional levels that require alignment.