Patent ID: 7172648

Claim:
An oil-based ballpoint pen ink composition, comprising at least one solvent selected from 3-methyl-1,3-butanediol, 1,3-butanediol, 3-methyl-3-methoxy-1-butanol and 3-methoxy-1-butanol, said at least one solvent being contained in an amount of at least 50 mass % of all solvents in said ink composition, said ink composition further containing at least one surfactant selected from the group consisting of: a) a polyoxyethylene alkyl ether represented by the following formula: Râ€”Oâ€”(CH 2 â€”CH 2 O) n H wherein R is an alkyl group and n is an integer of three or more, b) a fatty acid polyoxyethylene alkyl ether represented by the following formula; wherein R and R 1 each is an alkyl group and n is an integer of three or more, c) a polyethylene glycol fatty acid ester represented by the following formula: where R is an alkyl group and n is an integer of three or more, d) a polyoxyethylene glycerin fatty acid ester represented by the following formula; wherein R is an alkyl group, and n and in each is an integer of one or more, and the total of n and m is three or more, e) a polyoxyethylene sorbitan fatty acid ester represented by the following formula: wherein R is an alkyl group, and 1, m and n each is an integer of one or more, and f) and a surfactant selected from said surfactants and having an HLB of 7 to 16 and an oily appearance at 25Â° C. wherein the addition molar number of ethylene oxide constituting said surfactant is from 3 to 50, the alkyl group contained in said surfactant is an alkyl group derived from an acid or an alcohol and having from 10 to 30 carbon atoms, and said surfactant is blended in an amount of 0.1 to 20 mass % in total based on the ink composition.