Surgical ink, production method for said ink, and surgical pen using said ink

A surgical pen having radiation resistance, comprising:

• a cylindrical shaft body portion having a storage part for a surgical ink;
• and
• a pen tip portion for discharging the ink at a distal end of the shaft body portion,
• wherein the pen tip portion is made of a synthetic resin, and has a bending strength of 1.0 N or more after irradiation with γ-rays of 25 kGy to 70 kGy,
• the surgical ink comprises an activated carbon powder and a water-soluble organic solvent,
• the surgical ink comprises
• 60 to 80 parts by weight of a dispersion liquid containing 8 to 10 wt % of the activated carbon powder, 5 to 7 wt % of a water-soluble polymer, 0.01 to 1.00 wt % of sodium hydroxide, and water as a residue;
• and
• 5 to 25 parts by weight of the water-soluble organic solvent, and
• the surgical ink has a pH of 4 to 11, an average particle diameter of 150 to 310 nm, and a viscosity of 2.0 to 8.0 mPa·s after irradiation with γ-rays of 25 kGy to 70 kGy.