| 摘要 |
PROBLEM TO BE SOLVED: To cope with a high-resolution and high-speed ink-jet system, by adding particles of a dry polymer which swells with water to be hydrogel and has a specific dry average particle size. SOLUTION: An average particle size of hydrogel particles in a state when dried is 0.05-3 μm, most preferably 0.2-1 μm. For producing the hydrogel particles, crushing, a hydrogel formation method, or a method of precipitating and polymerizing a watersoluble unsaturated monomer in an organic solvent is carried out. In the precipitation polymerization method, a water-soluble unsaturated monomer selected from quaternary compounds such as acrylic acid, etc., or a crosslinking water-soluble monomer having two or more polymerizable unsaturated bonds in a molecule, e.g. methylene bisacrylamide, bisacrylamide acetate or the like is polymerized with the use of an initiator which is dissolved in an organic solvent decomposing monomers, but not decomposing polymers. Then particles generated through the precipitation are separated from the solvent and swollen with water. |
