| 摘要 |
PURPOSE:To obtain a copy image of high quality which causes neither variation in the charging amount of toner nor sticking transfer to a vinyl chloride sheet due to the repetition of copying operation by using specific carbon black as the black pigment of the toner. CONSTITUTION:Carbon black which has <=50ml/100g DBP oil absorption, >=40mum mean grain size (primary grain size), and <=6.0pH carbon black is used as the black pigment of the toner. The carbon black is acidic, so less carbon black is absorbed by polyester resin having an acid group during kneading, the carbon black is exposed easily in particle surfaces, and the excessive accumulation of a charge in the toner is evaded, so that there is no decrease in image density due to the repetition of copying operation. Further, the carbon black is made acidic to improve the dispersibility of the polyester resin, and the use of the carbon black having small oil absorption prevents the localization of the toner and defect in fixation, thereby obtaining a copy image of high quality. |
