It is well known that piezo inkjet technology is capable of depositing a controlled amount of fluid in a specified location very accurately. This technology renders itself well to various deposition applications. We have conducted research to apply inkjet technology to patterning devices. In order to achieve high rates of production throughput, multi-nozzle inkjet heads are needed. One of the issues with multi-nozzle heads is the drop weight variation between channels. The inkjet heads used for this research have 128 piezo-electric elements in line. An analog drive circuit, which creates a trapezoidal waveform, is connected to the common electrode of all elements. The other ends of piezo elements are connected to individual switches. The element discharges on the leading edge of the trapezoid waveform if the other end is grounded by the switch. This causes the element to shrink and pull back the meniscus at the orifice. When it is charged on the trailing edge, the element expands and pushes the meniscus out through the orifice. The discharge level, which influences drop volume, can be controlled by adjusting the duration of the grounding time of the switch. By using this method, it has been shown that the drop weight variations across the 384 nozzles (three heads) can be improved from 25-27ng±20% to 25-27ng±5%.
Shinya Kobayashi, Hitoshi Kida, "New Drive Electronics to Improve Drop Weight Uniformity in Multi-Nozzle Inkjet Heads" in Proc. IS&T Digital Fabrication Conf., 2005, pp 17 - 20, https://doi.org/10.2352/ISSN.2169-4451.2005.21.2.art00008_3