Abstract: A process of forming a composite toner image, for example, a two color image, includes steps of charging and exposing an image member to create a first electrostatic image and developing the image to form a first toner image. The process is repeated to form two toner images on the same area or frame of an image member. To reduce the tendency of the first toner image to spread into the second electrostatic image and also to reduce scavenging of the first toner image by the second toning step, the image member is exposed, immediately after the formation of the first toner image, to uniform activating radiation to form charges of a polarity opposite the electrostatic image, which charges tend to hold the first toner image to the image member. The uniform exposure can be effected through a transparent support to the image member.

Abstract: A two component development system includes developer with charged toner particles and oppositely charged carrier particles having high coercivity and permanent magnetism. The developer is moved through a development zone on a shell and into contact with an image member carrying an electrostatic image by rapidly rotating a magnetic core within the shell. The core has alternating magnetic poles around its periphery. To prevent carryout of carrier on the image member, an AC bias is impressed across the development zone.

Abstract: An electrostatic latent image on a photoconductor of an electrophotographic device is developed by a gray scale monocomponent nonmagnetic development system using a combination of AC and DC bias voltages applied to a developer roller and a monocomponent nonmagnetic developer applied to the developer roller by an adder roller. The developer comprises a mixture of toner particles charged to one polarity and transparent beads charged to the opposite polarity, by triboelectric charging in bulk in an alternating field between the two rollers, rather than by friction contact with apparatus surfaces. The adder roller applies the charged mixture to the developer roller for developing the latent image in an electric field to an image density determined by the magnitude of the DC bias. A DC bias may be applied to the adder roller, especially to provide a gradient relative to the DC component of the developer roller bias for driving the bulk charged mixture onto the developer roller.

Abstract: In a single-component developer system, the charge of the developer is controlled despite changes in relative humidity by determining or predicting the relative humidity and adjusting the bias on a device for charging said toner, such as, a toner-adder roller or doctor blade.