Aqueous pigment ink

摘要

According to one embodiment, an aqueous pigment ink includes water, a pigment, and a water-soluble polymeric compound. The pigment is contained in the aqueous pigment ink in an amount of less than 5 wt%. The aqueous pigment ink has viscosities (mPa·s) measured at 25°C using a cone-plate type viscometer and satisfying the following relationships: 0 ‰¤ V B - V A / V B < 0.05 V C / V A ‰¥ 1.5 3 mPa ‹ s ‰¤ V A ‰¤ 15 mPa ‹ s wherein V A represents a viscosity measured at a rotation speed of 50 rpm, V B represents a viscosity measured at a rotation speed of 2.5 rpm, and V C represents a viscosity measured at a rotation speed of 50 rpm after adding calcium chloride in an amount of 0.5 wt% of the aqueous pigment ink.