| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an aqueous ink in which permeability to plain paper and image density of a recorded image obtained are high, and dispersion stability is excellent. <P>SOLUTION: The aqueous ink has a surface tension of 34 mN/m or less including a self-dispersion pigment and water. In the aqueous ink, the self-dispersion pigment has a plurality of pKa values that are 8.0 or less. Assuming that the lowest pKa value among the plurality of pKa values is pKa<SB>1</SB>and the highest pKa value among the plurality of pKa values is pKa<SB>2</SB>, pKa<SB>1</SB>and pKa<SB>2</SB>satisfy Mathematical formula (1), and the pH value of the aqueous ink satisfies Mathematical formula (2).Mathematical formula (1): 2.0≤pKa2-pKa1.Mathematical formula (2): pKa2-1.5≤pH≤pKa2+0.5. <P>COPYRIGHT: (C)2011,JPO&INPIT |
