Patent ID: 8406668

Claim:
A fixing device comprising: a fixing roller; a heating member; an fixing belt supported around the fixing roller and the heating member with tension, wherein the fixing belt is endless, and; a pressure member facing the fixing roller with the fixing belt interposed therebetween, the heating member being in contact with the fixing belt to heat the fixing belt, and in a fixing nip region formed by the fixing belt and the pressure member, a toner image borne on a recording medium being heated and pressurized to be fixed on the recording medium, wherein a heating section that is in contact with the fixing belt to heat the fixing belt in the heating member is formed with a planar heat generating element that extends along an axial direction of the fixing roller and has a positive resistance temperature characteristic; wherein the planar heat generating element includes a first electrode and a second electrode, where the electrodes are at both ends in a circumferential direction of the planar heat generating element so that current flows only in one direction from the first electrode to the second electrode throughout the planar heat generating element and the one direction is a direction substantially orthogonal to a longitudinal direction which is a direction extending along the axial direction of the fixing roller in the planar heat generating element, and has a heat generating layer that generates heat when current is supplied from the electrode, and the heat generating layer is constituted so that both ends in a longitudinal direction of the heat generating layer have larger thickness than that of a center part thereof; wherein the heating section of the heating member is formed with the planar heat generating element on an outer or inner circumferential surface of a substrate having a substantially semicircular shape made of a material having high thermal conductivity, and has a coat layer capable of reducing a frictional force between the fixing belt and the heating member on a surface in the side in contact with the fixing belt; wherein the planar heat generating element has at least the heat generating layer that generates heat by current supplied from the electrode and an insulating layer; and wherein the heat generating layer is made of a composite material in which heat-resistant polymer of an organic material or an organic and inorganic composite is filled with a conductive filler.