Self-dispersing polymer, an aqueous dispersion, an aqueous ink composition, and an ink set, and an image forming method

PROBLEM TO BE SOLVED: To provide an ink composition having stable delivering properties and good fixity, conventionally unavailable. SOLUTION: A water-based ink composition comprising a colorant-containing water-insoluble colored particle (A) and a self-dispersible polymer (B) is provided, wherein the self-dispersible polymer comprises a hydrophilic constituent unit and a constituent unit derived from an aromatic group-containing monomer, the content of the constituent unit derived from the aromatic group-containing monomer is ≥10 mass% but ≤95 mass% and the content of the water-soluble component exhibiting water-solubility in dispersed state is ≤10 mass%. COPYRIGHT: (C)2009,JPO&INPIT