| 摘要 |
PROBLEM TO BE SOLVED: To obtain the subject pigment ink composition not making ink leakage from a pen point, even when a ballpoint pen is allowed to stand in a quiet condition, not generating a blot, even when used for writing at a high temperature, and having a stable writing performance not changed with the lapse of time, by compounding a specified polymeric compound. SOLUTION: This pigment ink composition is obtained by adding (E) a reversibly and heat-sensitively gelling polymeric compound having a gelation-starting temperature of 30-50 deg.C [for example, poly(N-isopropylethylacrylamide), poly(N- isopropylmethacrylamide), poly(N-cyclopropylacrylamide) and poly(N,N- diethylacrylamide)] in an amount of, preferably, 0.05-15 wt.%, more preferably, 0.1-10 wt.% to an aqueous ballpoint pen pigment ink composition containing (A) a pigment (an ordinary inorganic or organic pigment), (B) a pigment dispersing agent (for example, a polyacrylate-styrene copolymer), (C) a water-soluble solvent (for example, propylene glycol), and (D) a water-soluble polymeric resin (for example, tragacanth gum) as main components. |
