Abstract: An oil-based ink composition for a ball-point pen that enables suppression of a blobbing phenomenon by controlling the internal cohesion force of an ink is provided; An oil-based ink composition for a ball-point pen at least comprising a colorant, a resin, and from 0.01 to 1.5 % by weight of a high polymerization degree polybutyl vinylal with a polymerization degree of 900 (theoretical molecular weight of 60,000) or more and comprising, as a main solvent, a solvent selected from alcohols, polyhydric alcohols, and glycol ethers with a vapor pressure at 25° C. of 0.001 mmHg or higher by 50% or more for the entire solvent.

Abstract: Oil-based ink composition for a ballpoint pen, involving at least a coloring material, a resin and a solvent selected from the group consisting of an alcohol, a polyhydric alcohol and a glycol ether each having a vapor pressure of 0.001 mmHg or more at 25° C. as a main solvent and further involving a phosphoric acid ester neutralized material; in order to provide an ink composition for a ballpoint pen which suppresses blobbing of a written letter at the start of writing and is capable of being excellent in a soft smooth feeling on writing.

Abstract: In order to provide an ink composition for a ballpoint pen which suppresses blobbing of a written letter at the start of writing and is capable of being excellent in a soft smooth feeling on writing and an oil-based ballpoint pen using the ink composition, there is provided an oil-based ink composition for a ballpoint pen, involving at least a coloring material, a resin and a solvent selected from the group consisting of an alcohol, a polyhydric alcohol and a glycol ether each having a vapor pressure of 0.001 mmHg or more at 25° C.

Abstract: An oil-based ink composition for a ball-point pen that enables suppression of a blobbing phenomenon by controlling the internal cohesion force of an ink is provided; An oil-based ink composition for a ball-point pen at least comprising a colorant, a resin, and from 0.01 to 1.5% by weight of a high polymerization degree polybutyl vinylal with a polymerization degree of 900 (theoretical molecular weight of 60,000) or more and comprising, as a main solvent, a solvent selected from alcohols, polyhydric alcohols, and glycol ethers with a vapor pressure at 25° C. of 0.001 mmHg or higher by 50% or more for the entire solvent.