PRODUCTION OF FUSED POLYCYCLIC RED PIGMENT AND OPTICAL ELEMENT PREPARED BY USING THIS PIGMENT

摘要

PROBLEM TO BE SOLVED: To produce a fused polycyclic red pigment which is fine, has a uniform particle size distribution, and is improved in clearness and transparency by continuously adding a sulfuric acid solution of a fused polycyclic red pigment to running water. SOLUTION: One (1) pt.wt. fused polycyclic red pigment comprising an anthraquinone red pigment or perylene red pigment is dissolved in 3-50 pts.wt. sulfuric acid having a concentration of 70-100wt.% to obtain a sulfuric acid solution. One (1) pt.wt. this solution is continuously added dropwise to 3-50 pts.wt. running water at 5-25 deg.C to precipitate the fused polycyclic red pigment.