| 摘要 |
PROBLEM TO BE SOLVED: To obtain a sharp toner image and to improve image density by incorporating fine particles specified in pH into a surface layer. SOLUTION: This developing roller consists of a conductive shaft as a center axis and a single layer or plural layers successively and concentrically formed around the shaft. The surface layer contains fine particles of <=5 in pH. The surface layer is a conductive elastic layer or an outermost layer covering the conductive elastic layer. The particle size of the fine particles to be incorporated is <=30μm, and especially preferably 20μm. Further, fine particles of <=3.5 in pH are preferable considering the efficiency to electrify the toner into negative charges. Especially a colloidal silica or carbon black subject to acid surface treatment are preferably used. If the amt. of the fine particles incorporated into the surface layer is too large, the surface layer is made too hard. Therefore, the amt. of the particles is preferably controlled to <=20 pts.wt. based on 100 pts.wt. of a resin. |
