Liquid ejection head and driving method thereof

摘要

A liquid ejection head includes a passage unit (4) and an actuator (21). A nozzle (8) for ejecting liquid and a common liquid chamber are formed in the passage unit. An individual liquid passage (32) formed in the passage unit includes a first passage, a pressure chamber (10), a second passage, and a restricted passage (12). The first passage communicates between the nozzle and the pressure chamber. The second passage communicates between the pressure chamber and the restricted passage. The restricted passage is smaller than the second passage in the sectional area perpendicular to the flow of the liquid. The actuator can selectively take a first state in which the volume of the pressure chamber is V1 and a second state in which the volume of the pressure chamber is V2 larger than V1. The actuator changes from the first state into the second state and then returns to the first state to eject the liquid from the nozzle. The individual liquid passage is designed so that Tc1 and Tc2 defined by predetermined expressions showing characteristics of the individual liquid passage satisfy a condition that Tc1/Tc2 is substantially not less than 4.7 and not more than 5.5.