Importance

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Abstract

In a printing system a first endless imaging member, such as a belt or drum, moves past an imaging station where it receives a dry toner image, and contacts a second endless imaging member to transfer the toner image to the second member. The first and the second imaging members are each operated isothermally with at least the second member at a temperature T2 higher than the softening temperature of the toner which, in turn, is above the temperature T1 of the first member. The first member has a hard abrasion-resistant and preferably smooth surface with a surface energy under about 20 dynes per centimeter, while the second member is both softer and has a higher surface energy, but still below that of the ultimate imaging substrate, e.g., paper, and has a thickness and compressibility that allow it to conform. In a preferred system, a charge-deposition cartridge deposits a latent charge image on a dielectric layer to attract and hold toner particles. A five micrometer thick surface layer of Teflon PFA simultaneously provides a suitable capacitance and low surface energy for the first member which is then developed with hard toner particles formed with a polymer having a softening temperature somewhat below the operating temperature T2 of the second imaging member. The second imaging member may be a belt having a woven Nomex carcass and an overlayer of silicone or fluorosilicone rubber elastomer having a Shore A hardness of approximately 50 to 80 durometer, to effect essentially complete image transfer between the first and second belts. In a multicolor system, separate imaging members for each color are successively brought into contact with and transfer their powder toner images in a softened state to a common transfer belt which applies the composite multicolor image to a final print.

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First Claim