In recent years, the electrophotography (xerography) technology adopted in multi-function machines and laser printers commonly used in the office is approaching the level of technology used in printing newspapers, brochures, and other paper media in terms of speed and image quality, because colorization was realized with rapid improvements made in speed and image quality. Since xerography technology enables, so is called, “on-demand printing” where different items are printed on each sheet, application of this technology is expected in various services, such as publishing personalized newspaper edited based on preferred interests, and the creation of customized direct mails according to an individual’s purchase history. Applying xerography technology to publishing machines poses certain challenges to overcome, however, such as realizing higher printing speed and supporting various types of paper.
Fuji Xerox therefore developed a flash fusing system. Figure 1 compares the differences between the flash fusing system and the heat roll fusing system applied in conventional laser printers. (For details of the mechanism of xerography, click here)
While the heat roll fusing system fuses toner images on paper by applying heat and pressure from the rolls (see Figure 1), the flash fusing system fuses toner images on paper in the following way: 1) the flash lamp applies intense light to the toner, 2) the toner converts absorbed light to heat, and then 3) the toner melts and is fused on the paper. Since the fuser does not directly contact the toner, the flash fusing system has the following characteristics appropriate for ultrahigh-volume printers.
1. Images are not deformed and sharp print quality is realized.
2. Various types of paper are supported, and paper jams and wrinkles are unlikely to occur.
3. No need for warm-up time or standby power.
4. Maintenance is easier because there are fewer mechanically operating parts (such as rolls) than in the heat roll fusing system.
The flash fusing system currently enables the high-speed color printing of 400 pages (A4 cut sheets) per minute.
Figure 1. Comparison between the Flash Fusing System and the Heat Roll Fusing System
Since flash fusing is a method in which toner absorbs light and converts it to heat, the toner must efficiently absorb light emitted from the xenon lamp (flash lamp). Although black toner has high absorption efficiency, that of color toner is low within the wavelength range where xenon lamp emissions are strong, making it difficult to fuse color toner on paper (Figure 2). Adding infrared absorber into the color toner can improve absorption efficiency, but can also change toner color because major infrared absorbers are not colorless and absorb light in the visible light range (Figure 3). Therefore, the flash fusing system was considered too difficult to apply in color printing.
Fuji Xerox optimized the relation between the spectrum attributes and fusing capability of the flash lamp and infrared absorbers through simulation, and developed a new color toner that maintains color without change and can be fused on paper using the flash fusing system. Fuji Xerox also optimized the flash lamp’s light emission method and successfully developed a fusing system appropriate for color-on-demand printing. This fusing system is now being introduced in ultrahigh-volume printers.
Figure 2. Toner Absorption Spectrum and Flash Lamp Emission Spectrum
Figure 3. Light Absorption Spectrum of Major Infrared Absorbers
Toner color changes because infrared absorbers are not colorless and absorb light in the visible light range (400-700 nm).
GLOBAL | Overseas
