Patent ID: 8328345

Claim:
A method of forming a dense image in non-aqueous inkjet composite printing wherein a black ink and at least one color ink are ejected in the same printing scan, comprising the step of: using the black ink comprising a pigment, a pigment dispersant, and a solvent, wherein an acid value of the pigment (P A ), a base value of the pigment (P B ), an acid value of the pigment dispersant (D A ), and a base value of the pigment dispersant (D B ), all measured by using a glass electrode as an indicator electrode and a silver/silver chloride electrode as a reference electrode, satisfy the following formula (1): | W P Δ P +W D Δ D |<3.0 (1) wherein Δ P =P A −P B ; Δ D =D A −D B ; W p represents the pigment content in % by mass in the ink; W D represents the pigment dispersant content in % by mass in the ink; and the unit of P A , P B , D A , and D B is meq/g.