| 摘要 |
PROBLEM TO BE SOLVED: To provide an ink set, which ensures no blotting at the boundary between a yellow ink and a black ink, by adding a specified ratio of an Ni ion to a black ink in an ink set composed of two or more colors including yellow and black. SOLUTION: An Ni ion is added, in an amount of 0.001 wt.% or above, to a black ink of an ink set, which comprises a colorant, a wetting agent and a surface active agent dispersed or dissolved in water. The Ni ion is added after preparation of the black ink. Especially, a greater effect can be expected when Pro-jet Fast Yellow 2 (commercial name of Zeneca Co., Ltd.) is used as a colorant for yellow ink. In the ink set, it is preferred to adjust the pH of the black ink to 7 to 10 and the pH of the yellow ink to 8 to 11. For a pH adjustor, there is used a substance, which does not adversely influence the inks to be prepared, e.g. an alkali metal hydroxide or the like. |
