MODIFIED INK JET DESIGN TO REDUCE KOGATION
Original Publication Date: 1991-Dec-31
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
A modified ink jet device design to reduce kogation caused by excess ink heating is disclosed. The modification increases rates at which a heater cools after a gas bubble has been generated from previous heatings. A rapid cooling rate of the heater is desired to reduce the tendency of pigment based ink formulations to kogate, that is, to leave material deposits on the heater. The modified ink jet device design accomplishes rapid cooling without interfering with the heat that is necessary for raising ink temperature to bubble nucleation levels for subsequent heating cycles. The modified ink jet device design comprises placing a highly thermally conductive over layer 1 of, for example, beryllium oxide (BeO) or diamond thin film over a polysilicon resistor 2 in the ink jet heater head as shown in the Figure. Vias 3 that pass through the oxide coating 4 allows the Be0 or diamond over layer 1 to make direct thermal contact with the silicon substrate 5. The Be0 or diamond layer extends beyond the edges of the polysilicon resistor 2 thereby overlapping and contacting the silicon substrate 5. The width of the overlap, that is the width of the viases 3 (e.g. 4 microns), is greater than the thickness of the thermally conductive overlayer 1 (e.g. 2 microns). The modified device design reduces: kogation, cavitation damage and power consumption over many heating cycles.