BALLPOINT PEN REFILL AND RETRACTABLE BALLPOINT PEN USING THE SAME

PROBLEM TO BE SOLVED: To provide a ballpoint pen refill with which handwriting showing good thermal discoloration function can be formed without causing discoloration of initial handwriting obtained by removing a resin film formed on a ballpoint pen tip pointed end portion, and to provide a retractable ballpoint pen using the ballpoint pen refill.SOLUTION: A ballpoint pen refill 1 and a retractable ballpoint pen using the same are provided. The ballpoint pen refill 1 includes an ink housing tube 5 with a ballpoint pen tip 2 attached thereto. The ink housing tube 5 houses an ink composition 6 including microcapsule pigments containing a reversible thermochromic composition. The reversible thermochromic composition has such a coloring state that the reversible thermochromic composition starts color fading when temperature reaches a color fading start temperature tduring temperature rise from a colored state, comes into a completely colorless state in a temperature range at or higher than a complete color fading temperature t, starts coloring when the temperature reaches a coloring start temperature tduring a temperature fall, comes into a completely colored state in a temperature range at or lower than a complete coloring temperature t, and is selectively held at the colored state or the colorless state in a temperature range between tand t. The ballpoint pen refill 1 has a resin film 7 bonded at a ballpoint pen tip pointed portion for preventing drying of a pen tip, the resin film 7 being made of two-part curable resin composition.