Patents by Inventor Rudolf Groh

Rudolf Groh has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Thermoplastics sheets or composite sheets with optical inhomogeneities
    Patent number: 4098940
    Abstract: The present invention is related to a sheet or a composite sheet made of transparent thermoplastics with optical inhomogeneities according to a desired and reproducible pattern, which are not discernible with an unaided eye, and which produce polarization-optical patterns when placed in a polarization-optical arrangement. The invention is further related to a process for the manufacture of such a sheet or composite sheet and to their use for the manufacture of counterfeit-proof official documents.
    Type: Grant
    Filed: August 31, 1976
    Date of Patent: July 4, 1978
    Assignee: Hoechst Aktiengesellschaft
    Inventors: Rudolf Groh, Gustav Meinel