Oil-Based Ink Composition for Ink Jet Recording and Method for Inspecting It

A process of producing an oil-based ink composition for ink jet recording, in which at least a pigment component represented by the following general formula (2) is dispersed in a mixed solvent comprising a polyalkylene glycol dialkyl ether represented by the following general formula (1) and a lactone solvent in an amount of 0.02 to 4 parts by mass per 1 part by mass of said ether into an oil-based ink composition,

• characterized in that when a measuring sample prepared by adding 2 ml of N-methyl-2-pyrrolidone and 8 ml of acetonitrile to 100 mg of said d-based ink composition is analyzed by means of high speed liquid chromatography under the following measuring conditions, the concentration of a component having a peak at a holding time of 10.3 minutes is set at 0.4 ppm or less:
• R11—(OR13)n—OR1 General Formula (1)
• where R11 and R12 that may be identical with or different from one another, are each an alkyl group having 1 to 3 carbon atoms, R13 is an ethylene or propylene group, and n is an integer of 2 to 4;
• where R stands for a hydrogen atom, a methyl group or a chlorine atom;
• and
• Measuring Conditions for High Speed Liquid Chromatography
• an ODS column of 4.6 mm in inner diameter and 25 cm in length is used;
• water (liquid A)/acetonitrile {liquid B) is used as an eluting solution at a flow rate of 1.0 ml/min and at such a mixing ratio that there is linear gradient elution occurring, wherein the eluting solution flows at a constant 50% by volume/50% by volume (A/B) from the start of elution (0 minute) to the elapse of 1 minute, and at a rate varying from 50% by volume/50% by volume (A/B) to 0% by volume to 100% by volume (A/B) from the elapse of 1 minute after the start of elution to the elapse of 25 minutes;
• the column temperature is at 40° C.;
• and the detection wavelength is at 254 nm±4 nm.