PURPOSE: To obtain the subject particles having small diameters and narrow particle size distribution, excellent in dispersibility, image sharpness and long- term stability, etc., in sensitization of antigen antibody and useful for electrophotographic toners, carriers, etc., for diagnostic reagents.
CONSTITUTION: These particles are obtained by dispersing (A) a pigment containing 0-0.1wt.% of a Ca salt, e.g. a quinacridone derivative containing 0-0.1wt.% of a rosin Ca salt into an aqueous phase and subjecting (B) a monomer component containing a hydrophobic monomer such as methylstyrene to aqueous deposition polymerization using (D) a water-soluble radical polymerization initiator such as potassium persulfate in a concentration of 0.001-0.03(mol/l) and a concentration ratio to the component B of 0.004-0.10. Furthermore, the component A consists preferably of disperse aggregation particles having particle diameter of ≤10 times based on primary diameter of this pigment in water phase.
HAYASHI KENJI
KIKUCHI TOMOE
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