Manufacturing method of piezoelectric vibrator unit, manufacturing method of liquid jet head, piezoelectric vibrator unit, and liquid jet head

A manufacturing method of manufacturing a piezoelectric vibrator unit comprising a plurality of piezoelectric vibrators, the plurality of piezoelectric vibrators to which a drive signal is to be applied so that the plurality of piezoelectric vibrators are displaced in a direction, the plurality of piezoelectric vibrators including a first piezoelectric vibrator and a second piezoelectric vibrator each of which includes a piezoelectric material, the manufacturing method comprising:

• supplying a polarization drive signal, which is different from the drive signal, for charging and discharging the piezoelectric material alternately, to the plurality of piezoelectric vibrators so as to generate self-heating;
• after supplying the polarization drive signal, supplying a polarization voltage in the direction to the plurality of piezoelectric vibrators in which the self-heating is generated so as to polarize the plurality of piezoelectric vibrators;
• measuring a displacement amount of each of the plurality of piezoelectric vibrators after supplying the polarization voltage;
• setting a target displacement amount based on the measuring result, wherein the displacement amount of the first piezoelectric vibrator is less than the displacement amount of the second piezoelectric vibrator, and the target displacement amount is the displacement amount of the first piezoelectric vibrator;
• calculating a difference between the displacement amount of the second piezoelectric vibrator and the target displacement amount;
• setting a condition of a spot heating for the second piezoelectric vibrator based on the difference, the condition including a heating area, a heating time and a heating temperature at which the piezoelectric material of the second piezoelectric vibrator is depolarized and which is equal to or higher than Curie temperature;
• and
• performing the spot heating by applying a laser beam to a portion of the piezoelectric material of the second piezoelectric vibrator based on the condition so that the portion of the piezoelectric material of the second piezoelectric vibrator is depolarized and the displacement amount of the second piezoelectric vibrator is decreased.