Fuser rolls

For the above reasons, processes that involve combinations of heat and pressure are the most widely used. This is normally accomplished by hot-roll pressure devices in which at least one roll is heated with a quartz lamp (Lee, 1975 Prime. 1983 Kuo. 1984 Hiraoka et al.. 1993). Offset of the toner to the fuser roll can be avoided by the use of special oils wicked onto the surface of the roll. Most roller fusing devices use heated rolls coated with silicone or fluorocarbon elastomers. Composite layer structures with multiple layers for improved process lifetime are becoming more common. Figure 17 shows a cross-section of a typical fuser roller and Fig. 18 shows a typical fusing process. For a review of fusing materials, see Gruber et al. (1989). For a discussion of the effects of paper properties on fusing, see Sanders et al. (1996). 

During fuser-roll resist lamination processes, the copper-clad FR- substrate surface temperature was found to be inversely proportional to the substrate thickness. This temperature fluctuation has resulted in changes of adhesive forces in the copper/resist interface which in turn can affect the yield in the printed circuit manufacturing processes. By using infrared preheat... 

Ripsom and Wopschall suggested a linear relationship between logarithmic Riston 3600 resist viscosity and temperature. At 25 C, the resist viscosity was reported to be 10 poises. At 100 C, the viscosity would decrease to 10 poises. Hence, there is over 3 orders of magnitude drop in resin viscosity as the temperature is raised from room temperature to 100 C, which is 5 degrees below the typical fuser roll lamination... 

Dry Film Lamination The resist lamination was performed using a Model 712 Hot Roll Laminator supplied by MacDermid, Inc., Waterbury, Connecticut. The heart of the lamination system is an aluminum-cored fuser roll which is about 2.3 inches in diameter and is coated by 0.1 inch thick additives-filled silicon rubber. Figure 3 shows a schematic of the fuser roll. All dry film lamination experiments were performed using a conveyor speed of 20 inches per minute an air-assisted pressure of 0 PSIg and a fuser roll temperature of 103 C. The hold time between surfece treatment and resist lamination was kept constant at 60 minutes. 

Finally, Wilson (90) has pointed out a subtle but significant mechanical interface between the paper and the two rolls through which it must pass. As Figure 19 shows, paper tends to wrap itself around a hard fuser roll backed by a soft back-up roll, whereas it strips more reliably from a compliant fuser sleeve opposed by a hard backing roll. 

PVB is also used in toner formulations as a binder (19,120). PVB is added to the formulations to increase viscosity, to improve film integrity over the fuser roll, and to prevent blocking. The overall toughness of PVB enhances the integrity of the toner during the milling process and extended machine operation. This minimizes the level of fines without detracting from the flow properties. 

Silicone elastomers are encountered in a variety of applications, such as sealants used for baths and showers as well as other applications where gaps are to be filled with a water impervious flexible material, mouldings used in medical applications, fuser rolls in printers, etc. SiUcone elastomers are usually based on polydimethylsiloxane (PDMS). Linear PDMS is normally a hquid at ambient temperatures. Even the very high molar mass materials show viscoelastic rather than solid behaviour.The polymer is a simple flnear chain with terminal hydroxyl groups at each end. The of the backbone is about —90°C. 

Step 6 Fixing or fusing. The toner image is permanently fixed to the paper using either a heat-and-pressure mechanism (hot-roll fuser) or a radiant fusing technology (oven fuser) to melt and bond the toner particles into the medium (usually paper) being printed on. 

At the end of the process, the loose toner image is melted to fix it to the paper. We shall illustrate the interfaces involved for hot roll fusing, a process of choice for modern high volume duplicators. Radiant heaters, flash lamps, and cold pressure roll systems have all been incorporated in low volume copiers, whose intermittent mode favors instant start-up and low standby power. In continuous use, on the other hand, hot roll fusers have an approximately threefold advantage over their competitors in terms of power economy (.98) The toner comes into contact with more toner, with paper, and with the fusing roll. The first important interaction is one which must be avoided, and which therefore sets a temperature threshold for the materials and process it is a premature sintering ("blocking") of... 

Figure 19. Paper stripping from fuser is more reliable if the heated roll is deformable and the backup roll hard, than vice versa. (Reproduced, with permission, from Ref. 98. Copyright, 1979, Society of Photographic Scientists and Engineers.)...

---