Functionally seprated type toner for fixing with heated rolls

DETAILED DESCRIPTION OF THE INVENTION The mixing weight ratio of the low-molecular weight and high-molecular weight components is preferably from 75:25 to 55:45.
In the present invention, the weight ratio (A) of styrene to acrylic monomer in the low-molecular weight polymer component of a binder resin is varied from the weight ratio (B) of styrene to acrylic monomer in the high-molecular weight polymer component in such a way that A/B is greater than 1.
3.
At the same time, the ratio of the weight-average molecular weights (Mw) to number-average molecular weight (Mn) of the low-molecular weight polymer component is adjusted to be no higher than 3.
0, preferably no higher than 2.
5.
By satisfying these two requirements, the miscibility between the low-molecular weight and high-molecular weight polymer components can be significantly lowered to provide a structure that is microscopically separated in phase.
This is effective in solving one of the major problems of the prior art and enables anti-offsetting properties and low-temperature fixability to be controlled independently of each other.
In other words, low-temperature fixability is controlled by the low-molecular weight polymer component whereas anti-offsetting properties are controlled by the high-molecular weight polymer component.
As a further advantage, the tendency to form a microscopically phase-separated structure helps produce a fixed image having a surface layer that is rich in the high-molecular weight polymer component.
Thus, the surface layer is rich with the acrylic monomer of the high molecular weight polymer component, by virtue of the ratio A/B.
Because of this richness in the acrylic component, the miscibility with the plasticizer in a PVC sheet is sufficiently reduced to solve the problem of fouling of that sheet.
The reduced miscibility between the low-molecular weight and high-molecular weight polymer components offers the added advantage of greatly improving the efficiency of toner production because the low-molecular weight polymer component is friable and can be readily ground into particles