Electrothermal converting element board, ink jet printing head provided with electrothermal converting element board and ink jet printing apparatus using the same

An electrothermal converting element board comprising:

• a common electrode layer formed via a first insulating layer beneath an electrothermal converting element layer having a plurality of heat generating sections arranged on one straight line in correspondence to a plurality of liquid flowing paths, each having a liquid ejection opening on one end thereof for ejecting liquid used for a printing, and electrically connected to said plurality of heat generating sections, respectively;
• an individual electrode layer formed via a second insulating layer beneath said electrothermal converting element layer and electrically connected to at least one of said plurality of heat generating sections;
• a protective layer for covering said plurality of heat generating sections, said common electrode layer and said individual electrode layer;
• and
• a board section provided with said electrothermal converting element layer, said common electrode layer and said individual electrode layer;
• wherein a thickness of a portion of said protective layer covering said plurality of heat generating sections is smaller than that of a portion of said protective layer covering said individual electrode layer.

An ink jet printing head comprising:

• a liquid ejection member having a plurality of liquid flowing paths, each having a liquid ejection opening at one end thereof for ejecting liquid used for a printing,
• an electrothermal converting element board comprising a common electrode layer formed via a first insulating layer beneath an electrothermal converting element layer having a plurality of heat generating sections arranged on one straight line in correspondence to a plurality of liquid flowing paths, each having a liquid ejection opening for ejecting liquid used for the printing at one end thereof;
• said common electrode layer being electrically connected to the plurality of heat generating sections;
• an individual electrode layer electrically connected to at least one of the heat generating sections in the plurality of heat generating sections and formed via a second insulating layer beneath said common electrode layer and said electrothermal converting element layer, a board section provided with said electrothermal converting element layer, said common electrode layer and said individual electrode layer and
• a wiring board electrically connected to said electrothermal converting element board for supplying electric power to said common electrode layer of said electrothermal converting element board.