Polygram Gmbh

Adelbert Zielasek

Hermann Koop

Hermann Grobecker

Frederik B Nusselder

Erhard Schrode

Dieter Bartholdsten

Werner Heher

High storage density information carriers, particularly optically readable video discs and digital records, can only be read error-free by a playback device when the high requirements made of freedom from warping also remain guaranteed over long storage times. A cassette is provided to support and fix an information carrier only within its central portion which is free of information tracks and, by a sufficient spacing of the information carrier in the support-free area between a bottom portion and a cover portion contact with the information carrier in this area is avoided, even given consideration of maximally-admissible warping tolerances of the storage cassette and of the information carrier.

Storage cassette for high storage density, disc-shaped information

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.

Method for manufacturing disk-shaped information carriers

Growing community of inventors

Burgwedel, Germany

Adelbert Zielasek