DEVELOPING METHOD IN TWO COLOR ELECTROPHOTOGRAPHIC COPYING SYSTEM

摘要

PURPOSE:To eliminate edge effect in black color images and achieve higher quality by letting the developer used for development of red color images be of two component system and regulating the quantity of charging of the toner in this developer. CONSTITUTION:In copying images of red and black 2 colors by a two color electrophotographic copying system, edge effect appears in the black color images and lowers image quality depending upon the value of the quantity of charging of red color toner. Namely, a red color edging is produced through a white ground part W around the black color images B on the two color copies. Thereupon, when the quantity of charging of the red color toner is changed, the edge effect decreases with an increase in said quantity and at above a certain value, no edge effect is produced at all any more. When it is increased further, the density of the red color visible images gradually decreases. Hence, no edge effect is produced and if such a charging region of the red color toner where the image density of the red color visible images is sufficient is selected and copying is done at the charging quantity of the red color toner within this range, the production of the edge effect may be prevented.