Patent ID: 6536891
Filing Date: 2003-03-25
Classification: C09D

Abstract:
An ink set comprising at least two aqueous ink compositions each containing a dispersed pigment and a surfactant, said ink compositions including an ink composition having the lowest lightness and an ink composition having the highest lightness;wherein (1) said ink composition having the lowest lightness has a higher surface tension than those of other ink compositions; wherein (2) said ink composition having the highest lightness has a lower surface tension than those of other ink compositions; and wherein (3) the dispersed pigment contained in said ink composition having the lowest lightness and the dispersed pigment contained in said ink composition having the highest lightness are (3a) both anionic dispersed pigments or (3b) both cationic dispersed pigments, when condition (3a) is satisfied, (3a-i) said ink composition having the lowest lightness contains an anionic surfactant, and said ink composition having the highest lightness contains an amphoteric surfactant, or (3a-ii) said ink composition having the lowest lightness contains an amphoteric surfactant, and said ink composition having the highest lightness contains an anionic surfactant, and when condition (3b) is satisfied, (3b-i) said ink composition having the lowest lightness contains a cationic surfactant, and said ink composition having the highest lightness contains an amphoteric surfactant, or (3b-ii) said ink composition having the lowest lightness contains an amphoteric surfactant, and said ink composition having the highest lightness contains a cationic surfactant.