Ink-jet printing apparatus and method for varying energy for ink ejection for high and low ejection duties

An ink-jet printing apparatus using a printing head having an ejection port and a thermal energy generating element for generating thermal energy according to an applied energy to eject ink from the ejection port by pressure from a bubble generated in the ink by the thermal energy and capable of performing printing based on image data, the printing head having structure allowing a first ejection mode, in which ink ejection is performed in a state in which the bubble does not communicate with atmosphere, and a second ejection mode, in which ink ejection is performed in a state in which the bubble communicates with the atmosphere, to be switched in accordance with an amount of the energy applied to the thermal energy generating element, said apparatus comprising:

• means for controlling the energy applied to the thermal energy generating element correspondingly to an ejection duty obtained based on the image data, said means controlling the energy applied to the thermal energy generating element to be made relatively small when the ejection duty is high so as to perform ink ejection of the first ejection mode and controlling the energy applied to the thermal energy generating element to be made relatively great when the ejection duty is low so as to perform ink ejection of the second ejection mode.