Patent ID: 7883185

Claim:
An ink cartridge and its ink comprising a thermal ink-jet head provided with a heat resistor element that generates thermal energy for ejecting ink from an ejection opening, and storing the ink, wherein the ejection opening and the heat resistor element are directly oppositely disposed; and further comprising a protective layer on the heat resistor element, wherein the protective layer is arranged to protect the heat resistor element from the ink and is in contact with the ink, and wherein the protective layer contains at least one selected from the group consisting of a silicon nitride and a silicon carbide; and wherein the ink contains at least one of a polyvalent carboxylic acid and a salt thereof, and a total content of the polyvalent carboxylic acid and the salt thereof is in a range of from 0.001 mmol/l or more to 0.5 mmol/l or less.