Method for heating multiple piles of a laminate

A method for heat-sealing multiple plies of a laminate in a sealing region, wherein the laminate comprises a carrier layer of electrically nonconductive material and a sealing layer of thermoplastic material on at least one surface of the laminate, comprising the following steps:

• pressing the plies of the laminate together in the sealing region;
• and
• generating a high-frequency alternating electric field in the sealing region of the pressed-together plies of the laminate, so that the sealing layer is heated to a molten, fluid state,
• wherein the alternating electric field is generated at a first power level in a first subregion of the sealing region and at a second power level different from the first power level in at least one second subregion of the sealing region, thereby obtaining a differentiated heat distribution over the first subregion and second subregion due to a difference between the first power level and the second power level.