adjacent projecting points of the scallop pattern of 1 0 5 u03bcm 2 1 0 u03bcm 3 3 0 u03bcm and 4 5 0 u03bcm samples were prepared by combining the dimensions a with each dimension b then an sio film was formed by plasma cvd from the rear surface side of the substrate with a thickness of about 0 5 u03bcm on the lateral wall of the ink supply aperture and an orifice plate bearing a liquid flow path and a discharge port was adhered to obtain an ink jet recording head which was then subjected to a discharge durability test results are shown in tables 1 to 4 the discharge durability test was conducted under following conditions the test employed an ink having a composition of ethylene glycol urea isopropyl alcohol black dye water 5 3 2 3 87 parts the ink was discharged from the discharge port in response to a signal of a rectangular voltage of 30 v by 30 u03bcs and a frequency of 3 khz applied to the electrothermal converting member heater of the prepared ink jet recording head the aforementioned ink contained urea as a humidifying component for reducing ink evaporation and thus avoiding an ink clogging and the urea shows a weak alkalinity upon hydrolysis in case the lateral wall of the ink supply aperture is not protected sufficiently repeated droplet discharges with such alkaline ink induces a silicon dissolution into the ink resulting in a cogation scorched substance on the heater and eventually leading to a clogging of the liquid flow path.