The injection mould serves for the injection moulding of base plates for use as an information storage medium, for instance as a photoelectromagnetic plate or the like. Each moulding cycle comprises the following steps: filling a cylindrical mould cavity with molten resin, forming a central opening in the base-plate moulding and recompressing the base-plate moulding with the mould cavity closed. During recompressing, the base-plate moulding is pressed with high internal pressure against the walls of the mould cavity and against the outer wall of a cutting sleeve, with the result that the finished base-plate moulding has a high density and exhibits a smooth surface at the central opening. <IMAGE>
