Patent ID: 7445325
Filing Date: 2008-11-04
Classification: B41J

Abstract:
1. An ink tank which comprises an ink storage portion for storing an aqueous ink therein, having fine channels which retain the aqueous ink by capillary force, wherein: the aqueous ink comprises at least water and a water-soluble coloring material; and the aqueous ink further comprises a compound satisfying the following requirements (1) to (4): Requirement (1): a molecular weight of the compound is less than a molecular weight of the water-soluble coloring material; Requirement (2): part of a molecular structure of the compound is similar to part of a molecular structure of the water-soluble coloring material; Requirement (3): the number of carboxyl groups per molecule of the compound is more than the number of carboxyl groups per molecule of the water-soluble coloring material; and Requirement (4): a solubility of the compound in pure water with pH 7 at 25° C. is lower than the solubility of the water-soluble coloring material in pure water with pH 7 at 25° C.