Definitely, the ink-jet fabrication is an expectable technology for the field of display and semiconductor, like the fabrication of color filter, the forming of metal circuit, the dispensing of liquid crystal, and further continuous manufacture of flexible display etc. Why it hesitates to pace forward? The obstacle lies across is the jetting quality control, especially for the pixel-to-pixel variation. As minimum requirement for those applications, the 10% pixel variation is the threshold. In this article, an electrical controller was designed to differentiate waveform for each nozzle synchronously, to compensate the nozzle cell deformation and pressure drag loss during inkjet firing at high voltage and high frequency. The controller senses the variation of jetting fluctuation caused by pressure, temperature, and combined with the real observation analysis results, as a feedback circuit to modulate the driving waveform for each nozzle at versatile inks and environmental situations. It composed of a high voltage control block to drive each nozzle, a FPGA chip to multiplex all the high voltage output, an A/D converter to transfer analog signal to digital signal into FPGA, a differential signal input to FPGA as feedback to correct analog output, a real-time tracking of jetting quality to verify the nozzle-to-nozzle variation. By this design, the pixel-to-pixel variation can be acceptable and adaptable with the sharply environmental change.
Hsiang-Pei Ou, Chih-Jian Lin, Chieh-Yi Huang, Kevin Cheng, "Addressable Waveform Modulation for Ink-Jet Printing Realized by Self-Feedback Circuit" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP22), 2006, pp 103 - 105, https://doi.org/10.2352/ISSN.2169-4451.2006.22.1.art00026_1