Ink set for reducing printhead corrosion

#This invention relates to inkjet inks for inkjet printers. It has been developed primarily for minimizing corrosion of corrodible structures in printheads by dye-based inkjet inks.

#The following patents or patent applications filed by the applicant or assignee of the present invention are hereby incorporated by cross-reference.

#6,755,509 7,222,943 7,188,419 7,168,166 7,086,719 12/246,332 12/246,336 7,246,886 7,128,400 7,108,355 6,991,322 7,287,836 7,118,197 10/728,784 7,364,269 7,077,493 6,962,402 10/728,803 7,147,308 10/728,779 7,118,198 7,168,790 7,172,270 7,229,155 6,830,318 7,195,342 7,175,261 7,465,035 7,108,356 7,118,202 10/773,186 7,134,744 7,134,743 7,182,439 7,210,768 7,465,036 7,134,745 7,156,484 7,118,201 7,111,926 7,431,433 7,401,901 7,468,139 11/744,885 11/097,308 7,328,978 7,334,876 7,147,306 7,448,734 7,425,050 11/014,764 11/014,763 7,331,663 7,360,861 7,328,973 7,427,121 7,407,262 7,303,252 7,249,822 11/014,762 7,311,382 7,360,860 7,364,257 7,390,075 7,350,896 7,429,096 7,384,135 7,331,660 7,416,287 11/014,737 7,322,684 7,322,685 7,311,381 7,270,405 7,303,268 7,470,007 7,399,072 7,393,076 11/014,750 11/014,749 7,249,833 11/014,769 11/014,729 7,331,661 11/014,733 7,300,140 7,357,492 7,357,493 11/014,766 7,380,902 7,284,816 7,284,845 7,255,430 7,390,080 7,328,984 7,350,913 7,322,671 7,380,910 7,431,424 7,470,006 11/014,732 7,347,534 7,441,865 7,469,989 7,367,650 7,469,990 11/688,863 11/688,864 11/688,865 7,364,265 11/741,766 12/014,767 12/014,768 12/014,769 12/014,770 12/014,771 12/014,772 12/049,371 12/049,372 12/049,373 12/146,399 12/334,519 12/339,039 12/557,517 12/613,404 12/546,682 12/062,514 7,887,170 7,416,280 6,902,255 6,623,101 6,406,129 6,505,916 6,457,809 6,550,895 6,457,812 11/607,976 7,735,970 7,901,046 7,794,613 7,938,974 7,568,787 11/946,840 12/323,471 12/508,564 12/142,779 12/142,782

#Various embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which:—

#FIG. 1 is a perspective view of part of a thermal bubble-forming inkjet printhead having a silicon nitride nozzle plate and chamber sidewalls;

#FIG. 2 is a side view of one of the nozzle assemblies shown in FIG. 1, including CMOS layers;

#As foreshadowed above, the present invention minimizes corrosion of corrodible structures in inkjet printheads which are exposed to certain dye-based inks. The corrodible structures are typically silicon nitride, BPSG and, to a lesser extent, silicon oxide.

#Silicon Nitride Corrosion

#Initially, the present Applicant observed print defects in certain color channels of its inkjet printheads, most noticeably in black color channels. Forensic examination of such printheads using SEM microscopy revealed that a degree of roof delamination was occurring and it was posited that the dye-based ink was responsible for corroding silicon nitride structures in the nozzle chamber. Significantly, in printheads having a bilayered roof (an upper layer of silicon oxide and a lower layer of silicon nitride), the corrosion was most evident in the silicon nitride layer. Silicon surfaces in the printhead were observed to be resistant to corrosion by the dye-based inks.