Printing inks comprising an oxidation polymerization type resin, at least a part of which sets to gel in a non-polar ink solvent, a color agent, and an ink solvent, at least a part of which being a non-volatile polar solvent. When theoffset printing ink is applied onto an absorbent printing object, the non-volatile polar solvent is easily absorbed by the printing object to gel the oxidation polymerization type resin, thereby to allow the ink to dry quickly, whereas the ink on non-absorbent printing members of a printing machine does not dry easily.

OBJECT AND SUMMARY OF THE INVENTION 

This invention aims at overcoming the aforementioned drawbacks suffered by the conventional offset printing inks. An object of this invention is to provide a printing ink which has sufficient fluidity and dry slowly when being preserved or applied onto the printing component members of a printing machine, so as not to dry and be hardened easily even after the printing machine is put out of operation during the night, and which can dry quickly on an absorbent printing object such as paper so that, when the printed matters onto which the sheetfed offest ink is applied are put on top of each other, the ink applied onto the printed surface does not stick to the other printed object without need to spray anti-sticking powder on the printed surface of the printed object. 

To attain the above object on the invention, there is provided a printing ink comprising an oxidation polymerization type resin, a coloring agent, and an ink solvent, at least a part of the oxidation polymerization type resin being a resin which sets to gel in a non-polar ink solvent, and at least a part of the ink solvent being a non-volatile polar solvent. 

The printing ink according to this invention can maintain sufficient fluidity for a long period of time owing to the non-volatile solvent, when being preserved or applied onto non-absorbent members such as a printing plate in a printing machine, but can dry quickly when being applied onto an absorbent printing object such as paper because the oxidation polymerization type resin contained in the ink sets to gel at once as the non-volatile polar solvent is absorbed by the absorbent object. 

The other objects and characteristics of the present invention will become apparent from the further disclosure to be made in the following description of preferred embodiments.