Method of inkjet printing for use in point-of-sale systems

This invention relates to a method of inkjet printing, in particular for use in POS systems. In particular the printing method according to the invention is of the thermal type. In order to obtain high speed printing, for example of 15-20 lines per second when printing text on a paper medium 60-80 mm wide (for example receipts), the drops of ink ejected during the printing operation advantageously have a relatively large volume, i.e. not less than approximately 100 picoliters (pl) and preferably between 100 and 200 pl. The ink used for applications in POS systems must quickly penetrate an extensive range of paper media. This requirement is satisfied by using an ink having a surface tension of not more than approximately 35 dyne/cm (mN/m). Problems of stagnation and dripping of the ink caused by the printing conditions are overcome through the use of a nozzle plate coated with a wetting-resistant layer of silicon carbide. This coating material has proved to have non-wettability properties which do not significantly deteriorate during a printing operation over a long period of time.