NEGATIVELY CHARGEABLE DRY BINARY SYSTEM DEVELOPER

摘要

PURPOSE:To prevent the stain of a carrier and a photosensitive body with a toner and base fog and to improve durability by mixing a toner contg. at least a binding resin and a colorant and supporting hydrophobic silica having a specified hydrophobic degree on the surface with a silicone resin coated carrier. CONSTITUTION:A toner contg. at least a colorant and a binding resin and holding hydrophobic silica having 10-40 hydrophobic degree stuck to the surface is mixed with a silicone resin coated carrier to obtain the developer. The hydrophobic silica is obtd. as follows: silicon tetrachloride is hydrolyzed in an oxyhydrogen flame or precipitation is caused in an aq. sodium silicate soln. to form fine silicon dioxide powder, that is, hydrophilic silica and this silica is made hydrophobic by substituting an organosilicon compd. for silanol groups on the surface of the silica. The stain of the carrier and a photosensitive body with the toner and base fog are prevented and durability is improved.