PIGMENT DISPERSION AND OFFSET PRINTING INK COMPOSITION CONTAINING THE SAME

摘要

PROBLEM TO BE SOLVED: To provide a pigment dispersion containing a specified pigment dispersant and suitable for an offset printing ink, wherein the pigment of even a high concn. is finely dispersed in a stable state. SOLUTION: This pigment dispersion contains at least 0.2 pts.wt. modified novolak resin (A) and/or graft copolymer (B) as the dispersant for the pigment per 100 pts.wt. pigment. The resin (A) has at least one group of the formula I (Wherein 0 at the left end is derived from the novolak resin; w<1> and x<1> each represent a 1-19C divalent hydrocarbon group; (i) is 1 to 30; (j) is 0 to 30; and R<1> represents H or methyl) in the molecule. The copolymer (B) has a wt.- average molecular wt. of 3,000 to 100,000 and contains at least 100 molar % structural unit of the formula (II) (wherein w<2> and x<2> each represents a 1-19C divalent hydrocarbon group; (p) is 1 to 30; (q) is 0 to 30; and R<2> and R<3> each represents H or methyl) and a least 10 molar % structural unit of the formula III or IV (wherein R<4> is the same as R<2> ; R<5> represents H or a halogen; R<6> and R<7> each represents H or a 1-5C hydrocarbon group, a 1-5C alkoxy group, a 6-10C aryloxy group or a halogen; R<8> is the same as R<2> ; and R<9> represents a direct bond or a methylene group).