LIQUID JET RECORDING PROCESS AND APPARATUS THEREFOR

A recording apparatus comprises an inlet for accepting a liquid to be delivered to an outlet orifice through a liquid flow path. Liquid is supplied to the inlet for flow through the liquid flow path to a heating element, which heats liquid in the liquid flow path. Heating is sufficient to cause a change of state of the liquid (that is, to generate a bubble) and produce a force acting on the liquid which overcomes the surface tension of liquid at the orifice and thereby projects a droplet of liquid from the orifice. The temperature of the heating element is raised at each actuation to a temperature above the maximum temperature at which the liquid in the liquid flow path is subjected only to nucleate boiling so as to promote substantially instantaneous transfer of heat to the liquid proximate to the heating element and to retard the transfer of heat from the heating element to liquid at other locations in the liquid flow path. A processing circuit changes either the size or number of the projected droplets to effect tone gradation recording.