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

Abstract

The invention provides an oil-based ink composition for ink jet recording, which is best suited for printing onto polyvinyl chloride substrates, and improved in terms of both the stabilities of ink on storage and jetting, and a method for inspecting the same. The oil-based ink composition for ink jet recording comprises as a main solvent at least a specific polyalkylene glycol dialkyl ether and containing at least a specific quinacridone pigment component. That composition should be such that when a measuring sample comprising it is analyzed by means of high speed liquid chromatography under specific measuring conditions, the concentration of a component having a peak at the holding time of 10.3 minutes is 0.4 ppm or less.

1 . 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:
   R 11 —(OR 13 ) n —OR 1   General Formula (1)
 
   where R 11  and R 12  that may be identical with or different from one another, are each an alkyl group having 1 to 3 carbon atoms, R 13  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. 
 
       
     
     
         2 . The process for producing an oil-based ink composition for ink jet recording according to  claim 1 , characterized by further containing a binder resin, and a dispersant. 
     
     
         3 . (canceled)