Patent ID: 8733901

Claim:
A liquid discharge head substrate comprising: a substrate; a heating resistance layer provided on the substrate; a pair of electrode layers connected to the heating resistance layer; and a protection film configured to cover and protect at least a part of the heating resistance layer, wherein a part of the heating resistance layer positioned between the pair of the electrode layers is used as a heating portion for generating heat used for discharging liquid and a plurality of the heating portions is arranged to form an array of elements, wherein the substrate is provided with a supply port for supplying liquid to the heating portion, wherein the array is provided on both sides of the supply port along a direction in which the supply port extends, wherein a first region and a second region in which the protection film is thicker than that in the first region and which is provided surrounding the first region are provided over each of the heating portions, and wherein an area of the first region corresponding to the heating portion positioned at an end portion of the array in the direction in which the supply port extends is greater than an area of the first region corresponding to the heating portion positioned at a center portion of the array in the direction in which the supply port extends.