Water based ink compositions for ballpoint pen

摘要

A water based ink composition for a ballpoint pen containing ι-carrageenan in addition to a dye, water and a water-soluble organic solvent. When used in the ball point pen, the ink composition satisfies an ink drooling prevention and a drying resistance which are mutually incompatible functions and is excellent in writing performance regardless of containing a dye as a coloring agent. The ink composition (c) is used, for example, by accommodating a refill (12) whose ink accommodating tube (18) is filled with the ink composition and which is further loaded with an ink backflow-preventing member (20) in the ballpoint pen (10) whose writing edge is retracted and extruded from a front end opening of a barrel (21).

主权项

1. A water based ink composition for a ballpoint pen containing ι-carrageenan as an essential component of a viscous property controlling agent, in addition to a dye, a naphthalene-based dye intermediate, water and a water-soluble organic solvent, wherein a shear thinning index (n; 20° C.) of the ink composition obtained from the following experimental formula:
Experimental formula T=Kjn [T: shear stress (dyne/cm2), K: constant, j: shear rate (s−1), n: shear thinning index] is approximately 0.4 to 0.9 at a viscosity [cone and plate rotary viscometer (EL type: 20° C.)] of 1 or more and less than 20 mPa·s.