Abstract: This invention relates to an ink jet printing head comprising in combination: a thermal head member having at least one thermal element consisting of a plurality of thermal dot elements, a guide member having ink-supplied grooves contacting the thermal elements and being moved reciprocatingly, and a plurality of electrodes of different widths connected to each thermal element, whereby different-sized heated portions of the thermal element are obtainable, and it is possible to vary the amount of ink jetted in one dot. For a ratio of 1:3 for the widths of the electrodes (corresponding to the widths of the heated portions) in one dot, 16 printing density levels (16.times.4) can be obtained by printing four times for one dot. By combining four dots it is possible to obtain 64 printing density levels (16.times.4). The thermal dot elements can be arranged in either a zigzag pattern or in a continuous straight form.

Abstract: A thermal ink jet printing head is disclosed in which ink is fed from a reservoir to a recessed formation defined between two plates. The two plates are moveable with respect to each other. Between the two plates and connected with the recessed formation are a plurality of grooves corresponding to a number of adjacent dot elements. There are more grooves than dot elements, and ink resides within the grooves. Therefore, electrical signals sent to the dot elements cause heating of the thermal dots which cause the ink within the grooves to bubble and spray out of the grooves to a printing surface.