Patent ID: 7071245

Claim:
An oil-based ink ballpoint pen comprising an ink holding tube, a ballpoint tip provided at an end of said holding tube and an ink follower packed at the back of the ink composition in said ink holding tube for preventing evaporation of the ink from the holding tube, said ink composition comprising a) a colorant; b) two or more main solvents, wherein a first main solvent is 3-methoxy-3-methylbutanol or 3-methoxybutanol and a second main solvent is propyleneglycol monomethyl ether, the first main solvent and the second main solvent together comprise at least 50% of the total weight of all solvents; and c) a resin soluble in said solvents; wherein a proportion of said first main solvents and said second main solvent is in the range of 1/9 to 9/1 by weight, and the ink viscosity is 700–8000 mPa·s at 25° C.