Patent ID: 7950769

Claim:
An ink jet printing apparatus comprising: (a) an ink jet head comprising (1) a circuit board, wherein the circuit board comprises (i) a heating portion formed by a gap of an electrode wiring layer and a heating resistor layer; (ii) a protective layer formed over the electrode wiring layer and the heating resistor layer; and (iii) an upper protective layer which is arranged over the protective layer and includes at least a heat application portion which contacts an ink and is disposed over the heating portion so that the upper protective layer is configured to serve as an electrode to be electrically connected to cause an electrochemical reaction with the ink, and is made of a material including a metal which is dissolved by the electrochemical reaction and which does not form, on heating, an oxide film which hinders the dissolution; and (2) a flow path forming member having ink ejection orifices each corresponding to the heat application portion, the flow path forming member being joined to the circuit board to form an ink path leading to the ink ejection orifices; and (b) cleaning means for removing kogation deposited on the heat application portion by using the upper protective layer as one electrode to cause the electrochemical reaction and thereby dissolve the upper protective layer in the ink.