Patent attributes
An electric heater includes a substrate and a plane heating element disposed on one surface of the substrate. The plane heating element includes a first pattern portion including a start point and an end point, a second pattern portion that surrounds at least a portion of the first pattern portion and includes a start point and an end point, which are located at an innermost side of the second pattern portion, and a third pattern portion that surrounds at least a portion of the second pattern portion and includes a start point and the end point, which are located at an outermost side of the third pattern portion. The first pattern portion includes a plurality of first tracks that are space apart from each other and have an arc shape that is increasing in length from a center to an outermost side of the first pattern portion, the second pattern portion includes a plurality of second tracks spaced apart from each other and having an arc shape that is increasing in length from the innermost side to an outermost side of the second pattern portion, the third pattern portion includes a plurality of third tracks spaced apart from each other and having an arc shape that is increasing in length from an innermost side to the outermost side of the third portion, and a width of a third track is wider than a width of a first track.
