Patent ID: 7354960

Claim:
A water-based ink comprising colored microparticles containing a dye and a polymer dispersed in water, wherein each of the colored microparticles has a core/shell structure, the core comprising a polymer having an acetal group, a carbonic acid ester group, a hydroxyl group or an ester group in the molecule, the shell comprising a polymer made from a hydroxyethylmethacrylate monomer and a monomer having an unsaturated double bond in the molecule, wherein a total amount of monomer remaining in the colored microparticles is less than or equal to 5000 ppm based on the total weight of the water-based ink, and wherein the total amount of monomer remaining in the colored microparticles having a homopolymer converted solubility parameter (SF value) of not more than 20 (J/cm 3 ) 1/2 is less than or equal to 1,000 ppm.