| abstract |
The invention provides an ink containing a self-dispersion pigment in which a phosphonic acid group is bonded directly or through another atomic group to the surface thereof and a polyurethane polymer, wherein the surface charge amount of the self-dispersion pigment is 0.25 mmol/g or more and 0.42 mmol/g or less, and the polyurethane polymer has units respectively derived from a polyisocyanate, a polyether polyol having no acid group and a diol having an acid group. |