Patent ID: 6770688
Filing Date: 2004-08-03
Classification: C09D

Abstract:
A water based ink composition for a ballpoint pen which comprises (i) a thickener which is associative and swells in an alkaline medium, said thickener comprising a polymer having a carboxyl group and a hydrophobic group selected from the group consisting of a linear hydrocarbon, a halogenated alkyl, an organosilicon group, and a fluorinated carbon group, (ii) pigment particles having a diameter of 500 nm or less which have been subjected to surface treatment with a water soluble polymer and a surfactant wherein the water-soluble polymer is selected from the group consisting of stryene-acrylic acid resins, styrene-maleic acid resins, polyvinyl alcohol, polyethylene-polyethylene glycol copolymers, alginic acid, and cellulose, iii) a polar solvent comprising water and other water-miscible solvents and (iv) a pH controlling agent, wherein the pigment particle diameter is stable at room temperature over a 6 month period and the water based ink composition has a viscosity of 100 mPa.s or more.