BLACK PIGMENT FOR TONER COMPRISING MANGANESE OXIDE, METHOD FOR MANUFACTURING MANGANESE OXIDE, AND ELECTROPHOTOGRAPHIC TONER

摘要

PROBLEM TO BE SOLVED: To provide a black pigment for toner having high covering power and insulating property and to provide an electrophotographic toner having high insulating property and giving a high image density.

SOLUTION: The black pigment for a toner comprises manganese oxides MnOx (x ranging from 4/3 to 8/5) mainly expressed by Mn5O8having≥40 m2/g specific surface area and≥3,500 cm2/g covering power. The pigment is obtained by reacting an aqueous solution of manganese salts with an alkali aqueous solution to prepare a manganese hydroxide suspension, oxidizing the manganese ion at a temperature of≤65°C and heat treating at a temperature of 350 to 500°C.

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