Image development toner transfer

A transfer material has been developed for transferring monochrome and full-color images produced by a xerographic process or a dry toner printing onto a substrate. The process requires the use of a film from TPX as the transfer material. This material is used to transfer the xerographic or dry toner image onto the substrate with the application of heat and pressure (27). 

Figure 8 shows the xerographic process from the viewpoint of the toner. The material is fed into the development chamber, charged (usually by triboelectri-fication), and applied to the photoconductor surface. Powder which adheres to charged areas of the latent image is then transferred and fused to a sheet of paper or film the residue is cleaned off. Let us now consider these steps in greater detail. 

The final step in the development process involves the transfer of the toner particles from the carrier beads to the photoreceptor surface. The forces that bind the toner to the beads are electrostatic and van der Waals dispersion forces. Development thus requires that the forces due to the fields associated with the latent image exceed the forces that holds the toner to the carrier. For a discussion of processes by which toner particles are transferred from carrier beads to photoreceptor surfaces, see Schein (1975), Hays (1977, 1978), and Schein and Fowler (1985). For a discussion of the roles of van der Waals and electrostatic forces, see Gady et al. (1996). 

Now that the surface of the drum holds an electrical representation of the image being printed, its discrete electrical charges need to be converted into something that can be transferred to a piece of paper. The EP process step that accomplishes this is the developing step (Figure 7.12). In this step, toner is transferred to the areas that were exposed in the writing step. 

The photosensitive drum now has toner stuck to it where the laser has written. The photosensitive drum continues to rotate until the developed image is ready to be transferred to paper in the next step, the transferring step. 

A computer-controlled laser beam forms an image on a charged photosensitive drum. A carbon toner is applied and adheres to the charged areas, developing the image which is then transferred to the substrate and fixed with heat and pressure. Text, graphics and bar codes can all be produced this way. 

Ion deposition printers are used in similar circumstances, but their method of operation is different. A latent image is formed on a dielectric cylinder which is directly imaged by a projection of ions. Development is by a toner adhering to the charged areas and simultaneously transferred and fixed to the substrate under pressure. 

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