A high resolution, electrostatically-driven commercial inkjet head

A fully-micromachined, low power, large nozzle count and high resolution “electrostatically actuated inkjet (SEAJet^TM)” head has been developed for a POS printer. As 3D multiple-step structured nozzles are required for straight and high frequency ink ejection, it was formed by ICP deep-RIE employing a “multiple-step mask method” which makes troublesome stereo-photolithography unnecessary and 128 nozzles/chip were fabricated simultaneously. The required thin, 2 μm-thick pressure plates were formed by B doped etch-stop technology combined with two-step alkaline etching which enables smooth-surfaced and uniform (2.15±0.35 (3 σ)μm) pressure plates. The typical driving voltage is 26.5 V and the SEAJet head has achieved the uniform ink ejection up to a driving frequency of 18 kHz. The life of the actuator has been confirmed to be more than 4 billion times actuation. The typical printing speed of the POS printer is 15 1/s (lines per second) for a rolled paper and 3 ppm (papers per min.) for A4 paper in 360 dpi (dots per inch) high resolution, a performance level that makes this the fastest inkjet POS printer in the world. The average power consumption was measured as only 0.525 mW/nozzle. It is only one-thousandth of that of a typical thermal inkjet