A layer structure for producing a planar insulation laminate, including the following sequence of planar individual layers arranged one on the other: a B-stage resin, a glass fabric, a core layer made of polyester film, a glass fabric, and a B-stage resin. In the hardened state, an insulation material produced therefrom is suitable, for example, to be used as an insulation barrier between a low-voltage winding and a high-voltage winding of a transformer winding.