Polygram Gmbh

Erhard Schrode

Hermann Koop

Adelbert Zielasek

Dieter Bartholdsten

A method for manufacturing high information density storage disks, suitable for optical reading, out of transparent synthetics having a high glass temperature and high dimensional stability. The present injection molding method avoids potential double diffraction disruptive effects created by frictional or shearing forces. The synthetic material which is to be pressed is injected into one of the mold halves at a temperature that significantly exceeds the pressing temperature of the compression form and is injected so as to form a lump of the material. The pressing step wherein the compression form is closed down to a squeezing gap width is initiated prior to the termination of the injection operation. Likewise the cooling operation is initiated prior to the termination of the pressing step and both the cooling and pressing operations chronologically proceed at approximately an exponential rate.

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Lehrte, Germany

Erhard Schrode