| 摘要 |
PROBLEM TO BE SOLVED: To obtain a microparticulate composite oxide black pigment improved in a degree of blackness, tinting power and image sharpness by firing a microparticulate pigment precursor obtained by oxidizing a coprecipitate obtained by adding an aqueous alkali solution to a solution of a mixture containing a cobalt salt, a divalent manganese salt and an iron salt. SOLUTION: A mixture containing a cobalt salt, a divalent manganese salt and an iron salt in amounts to give a Co:Mn:Fe molar ratio of 1:(1.4-1.8):(0.2-0.6) and a Co/(Mn+Fe) molar ratio of 1/(1.9-2.1) is dissolved in water to obtain an aqueous solution having a concentration of 5-50wt.%. Thus solution mixed with an excess of a precipitant being aqueous alkali solution, and the mixture is aged for 5-20min to obtain a coprecipitate. An oxidizing agent is added to the liquid phase containing the coprecipitate to oxidize the coprecipitate to obtain a microparticulate pigment precursor. This precursor is washed with water, separated by filtration, dried by heating to 100-120 deg.C and fired to obtain a microparticulate composite oxide black pigment having a specific surface area of 30-100m2 /g. |
