Patent ID: 8263913

Claim:
A device comprising a planar heater, the planar heater including: an insulating substrate; an electric conductive film disposed on the substrate, an entirety of the electric conductive film having a planar sheet-like form, the electric conductive film having a substantially rectangular shape with four sides; a plurality of electrodes attached to one of the four sides of the electric conductive film while no electrodes are attached to the other three of the four sides; and an insulating film covering the electric conductive film, wherein the electric conductive film is formed of material having a resistance temperature coefficient of 420 ppm/° C. or higher at normal temperature, and wherein, upon turning on the planar heater, a portion of the electric conductive film proximate the one side heats up due to electric current flow between the plurality of electrodes, the heating up causing an electrical resistance of the portion to increase which subsequently causes the electric current flow to progressively flow through and heat up other portions of the electric conductive film which are continuously more remote from the one side.