Patent ID: 7076197

Claim:
A fixing device for fixing a recording sheet carrying a toner image, comprising: 1) a heating roller which rotates and comes into contact with a surface carrying the toner image, of the recording sheet, including, a cored cylinder, an elastic layer which is formed of a rubber on an exterior surface of the cored cylinder, and a toner releasing layer formed of a fluorine resin on a surface of the elastic layer; 2) a pressure roller which comes into contact with the heating roller to nip the recording sheet carrying the toner image, including, a heat source for heating the pressure roller, a cored cylinder for housing the heat source, an elastic layer formed of a rubber on an exterior surface of the cored cylinder of the pressure roller, and a toner releasing layer formed of a fluorine resin on a surface of the elastic layer of the pressure roller; and 3) an exterior heating roller which comes into contact with the heating roller to heat the heating roller, including at least one of, a heat source for heating the exterior heating roller, a cored cylinder for housing the heat source of the exterior heating roller, and a toner releasing layer formed of a fluorine resin on an exterior surface of the cored cylinder of the exterior heating roller; wherein Asker-C hardness of the heating roller is less than Asker-C hardness of the pressure roller, and wherein the heat conductivity of the elastic layer of the heating roller is equal to or less than 0.2 W/m K, and the heat conductivity of the elastic layer of the pressure roller is equal to or greater than 0.4 W/m K.