A double-sidedly self-adhesive planar element which is intrinsically heatable in a self-regulating way and at the same time has a particularly high flexibility. The planar element has a layer sequence of a posistor heating layer, a contacting layer and an adhesive layer, the contacting layer being a two-dimensional perforate contacting element which within the planar element is therefore present as a contacting element which has not been applied to a backing. Also disclosed is an adhesively bonded assembly of a bonding substrate and a planar element of the aforesaid kind, a method of producing a planar element of the aforesaid kind, and a method of using a planar element of the aforesaid kind for heating an adhesively bonded assembly.

A trimmable heater mat has a plurality of heater mat segments that together comprise a length of the heater mat. Each of the heater mat segments has a segment heater element connected to a power bus for generating heat. One or more of the heater mat segments can be severed from the others and removed from the heater mat to trim the length of the heater mat to a desired length. Heater mat segment boundary indicia on the heater mat indicate locations where one of the heater mat segments can be severed from the other remaining heater mat segments of the heater mat without interfering with the segment heater elements of the remaining heater mat segments or with the connections of the remaining segment heater elements to the power bus.

Aimed at achieving reliable joining between a heat element and an electrode, and high flexibility, provided as a solution is a sheet-like heater having an electrode area in which the electrode, a joining aid, and a porous heat element are stacked in this order, and the electrode area has at least one joined part in which the electrode, the joining aid and the porous heat element are joined.

Aimed at achieving reliable joining between a heat element and an electrode, and high flexibility, provided as a solution is a sheet-like heater having an electrode area in which the electrode, a joining aid, and a porous heat element are stacked in this order, and the electrode area has at least one joined part in which the electrode, the joining aid and the porous heat element are joined.