relationship between initial elongation percentages of the diaphragm and the diameters of ink dot deposited on a sheet substrate using a diaphragm made from a film of polyimide having a thickness of 10 micron millimeters the piezo electric actuator used in the tests was a multi layered having ten layers piezo electric member the ink was successively ejected by the application of a pulse signal between the electrodes having the maximum voltage of 35 volts and a period of 30 micro second the results are illustrated in fig6 which shows that the variation in the diameters of the deposited dots is decreased especially in the range of the initial elongation percentage of 0 15 to 3 of the diaphragm a continuous printing test was performed with use of the same recording head to examine the relationship of between the initial elongation percentages and the lifetimes of the recording head as a result of the test as shown in fig7 there exists a range of the elongation percentage of the diaphragm which allows the lifetime of the head to be extremely extended and it was found that the elongation percentages of the diaphragm exceeding the range cause the lifetime of the head to decrease sharply in the range of the elongation percentage from 0 15.