Patent ID: 7641316

Claim:
An ink jet head circuit board having a heating portion to generate thermal energy for ejecting ink as the heating portion is energized, the ink jet head circuit board compnsing: a substrate; a first electrode and a second electrode as a counterpart thereof, the first electrode having a first taper portion in which the thickness of an end portion of the first electrode near an area on the substrate between the first and second electrodes is gradually reduced toward the area, and the second electrode having a second taper portion in which the thickness of an end portion of the second electrode near the area is gradually reduced toward the area; a resistor layer continuously formed so as to extend on the area, a part of the first electrode including the first taper portion and a part of the second electrode including the second taper portion, the resistor layer on the area being used as the heating portion; a first insulating layer formed on the resistor layer except at least portions above the area, above the first taper portion and above the second taper portion; and a second insulating layer continuously formed so as to extend on the resistor layer and the first insulating layer, the second insulating layer being smaller in thickness than the first insulating layer.