Patent ID: 7681988

Claim:
An ink jet recording head using pigment ink as discharged ink, comprising: a nozzle member having a nozzle for discharging ink, the nozzle member having an ink-repellent layer forming a discharge port face having a discharge port that is an open end of the nozzle; and a projection portion positioned around the discharge port and protruding along a central axis direction of the nozzle with respect to the discharge port face, wherein the nozzle, in a cross section passing through the central axis of the nozzle, has an outline shape provided with a curved line having a changing radius of curvature, wherein an angle defined by tangent lines at points at which the curvature radius of the curved line is maximum and which are nearest to a boundary point at which the curvature radius of the curved line is minimum inside and outside the nozzle with respect to the boundary point is equal to or greater than 40° and equal to or less than 75°, and wherein a height of the projection portion from the discharge port face along the central axis direction of the nozzle is equal to or greater than 0.05 μm and less than 0.5 μm.