PURPOSE: To obtain good fixability without impairing a preservable property even with low heat energy by using a bisphenol F type epoxy resin having a specific repeating unit as the essential component of the above toner.
CONSTITUTION: The bisphenol F type epoxy resin having the repeating unit expressed by formula I is used as the heat fixing type toner essentially consisting of the epoxy resin. In the formula I, X denotes the group expressed by formula II, where n denotes 5 to 25 integer. There is a problem in the preservable property if the repeating unit n is <5 and in fixability if the n is ≥25. The bisphenol F type epoxy resin to be used therein has the characteristics of an extremely low melt viscosity as compared with the A type epoxy resin having the same softening temp. The weight average mol.wt. of the F type epoxy resin is preferably in a 3000 to 40000 range. The problem arises in the preservable property at 3000 and in the fixability at ≥40000, respectively.
ISHIYAMA MASAAKI
TAKAHATA HIROYUKI
