Shigetaka Fujiwara

Study of temperature and melting conditions during flash fusing

Temperature and melting conditions during flash fusing are studied. As a first step to clarify the microscopic behavior of toner, the temperature changes, considering thermal nonlinearity and the local melt viscosity dependence on the temperature changes, are examined. Consideration of the nonlinearity is performed by modification of the thermophysical properties employed in the temperature calculations, on the bases of the qualitative results of experiments. Suitable modification methods are a thermal conduction constant model and increment of the heat capacity model. The modification is necessary for the region from the start to the time the peak temperature appears on the toner surface. The local melt viscosity is analyzed by superposition of the calculated temperature changes and measured melt viscosity of the bulk toners. The melt viscosity varies a little with the kind of toner for the mid region in the toner layer. The melt viscosity calculated for the mid-region is one requirement determining the fixing strength. This means that to get good fixing strength, not only is it necessary to lower the melt viscosity, but also the thermophysical properties of the toner must be raised.

Dominant Factors For Fixing Strength In Toner Images: The Analysis Of Unsteady Temperature Distribution During Fusing

In the fusing process in electrophotographic machines, the temperature field and melting in the toner during fusing are important factors. As a first step leading to quantitative analysis, methods to measure the following conditions are developed: heat flux and unsteady temperature change on the toner surface by flash fusing, thermophysical properties of the toner and the paper, and toner deposit thickness and coverage. The measurement results are applied to the boundary conditions and thermophysical properties in an analysis using the finite element method. A model configuration is constructed with a toner layer and a paper layer. In this way, a one-dimensional unsteady temperature distribution is analysed. As a result of the analysis, the following points are made. During the time when fixing is performed, the maximum difference between the temperature on the toner surface and on the toner-paper interface is more than 200°C, regardless of the kinds of toner; this is attributed to very low thermal properties of the toner powder. At the same magnitude of fixing strength, the toner surface temperature level varies about 100°C with the kinds of toner. However, the toner-paper interface temperature is roughly the same regardless of the kinds of toner. Therefore, the interface temperature level is considered to be the lowest limit for fixing. On the other hand, the melt viscosity superposed on the temperature field varies little with the kinds of toner on the mid-region in the toner layer. It is also considered to be a requirement for fixing.