In methods for obtaining images by an electrophotographic printing method and an electrostatic printing method, electrostatic charge images formed on photosensitive materials are fixed after being developed with a toner which has been charged by friction.
Fixing systems include heat roller systems which fix developed toner images using pressurized heated rollers, and non-contact fixing systems in which fixing is accomplished using electric ovens or flash beam light.
For these processes to be performed smoothly, the toner must be able to hold a stable electrostatic charge, and must satisfactorily fix onto a paper.
In recent years, with the advancement of speeding-up, miniaturization, energy saving, and the like of printers, the toner is required to improve toner characteristics such as storage stability, low temperature-fixing property, and hot offset resistance.
A binder resin for toner exerts a significant influence on the above-mentioned toner characteristics. Heretofore, there have been used, as the binder resin, a polyester resin which is excellent in toughness and fixing property at low temperature, and has satisfactory performance balancing.
Meanwhile, from the viewpoint of a reduction in environmental burdens, such as control of global warming, an attempt has been made to replace a conventional plastic derived from a petroleum material by a plastic derived from biomass.
Use of a biomass material is required for the toner, and also use of a biomass material is required for the binder resin composing the toner.
Patent Document 1 discloses, as a polyester resin using a biomass material, for example, a polyester resin for toner in which isosorbide derived from a plant material is used as a polyhydric alcohol.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2010-285555