Liquid ejection head, liquid ejection method, and printing apparatus employing this ejection head

A printing apparatus comprising:

• a liquid ejection head, which includes
• a bubble generation chamber in which a liquid is to be retained,
• a heating resistor element arranged, facing the bubble generation chamber, so as to be able to heat the liquid retained in the bubble generation chamber,
• an ejection port that is formed open to eject the liquid retained in the bubble generation chamber,
• an ejection portion along which the liquid flows between the ejection port and the bubble generation chamber, and
• a liquid supply port employed to supply the liquid to the bubble generation chamber,
• wherein when the heating resistor element is driven and heats the liquid, a bubble is generated in the liquid retained in the bubble generation chamber, and forces the liquid to be ejected, and thereafter, the bubble becomes smaller and disappears without contacting the atmosphere;
• and
• a mounting unit on which the liquid ejection head is to be mounted,
• wherein ejection of the liquid is performed to print a printing medium,
• wherein when a length of the heating resistor element in a direction in which the liquid is to be supplied is defined by L, the center of gravity of the ejection port is shifted, at a distance of equal to or longer than L/7 toward a location of the liquid supply port, from the center of gravity on a surface of the heating resistor element, viewed in a direction in which the liquid is to be ejected, and
• wherein when a length of the ejection portion in the direction in which the liquid is to be ejected is defined as l and a length of the bubble generation chamber in the direction in which the liquid is to be ejected is defined as h, l/h is equal to or smaller than 2.

An ejection method, for ejecting ink from a liquid ejection head, the liquid ejection head including:

• a bubble generation chamber in which a liquid is to be retained,
• a heating resistor element arranged, facing the bubble generation chamber, so as to be able to heat the liquid retained in the bubble generation chamber,
• an ejection port that is formed open to eject the liquid retained in the bubble generation chamber,
• an ejection portion along which the liquid flows between the ejection port and the bubble generation chamber, and
• a liquid supply port employed to supply the liquid to the bubble generation chamber,
• wherein when the heating resistor element is driven and heats the liquid, a bubble is generated in the liquid retained in the bubble generation chamber, and forces the liquid to be ejected, and thereafter, the bubble becomes smaller and disappears without contacting the atmosphere,
• the ejection method comprising a step of:
• performing a process in which a bubble after expansion becomes smaller until disappearing, while maintaining a state where a height of a portion of the bubble that is at the rear from the center of the bubble in a direction in which the liquid is to be supplied form the liquid supply port to the bubble generation chamber is always greater than a height of the bubble that is in front of the bubble from the center in the direction.