Patents by Inventor Stephen Z. D. Cheng

Stephen Z. D. Cheng 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).

  • Negative birefringent polyimide films
    Patent number: 5344916
    Abstract: A negative birefringent film, useful in liquid crystal displays, and a method for controlling the negative birefringence of a polyimide film is disclosed which allows the matching of an application to a targeted amount of birefringence by controlling the degree of in-plane orientation of the polyimide by the selection of functional groups within both the diamine and dianhydride segments of the polyimide which affect the polyimide backbone chain rigidity, linearity, and symmetry. The higher the rigidity, linearity and symmetry of the polyimide backbone, the larger the value of the negative birefringence of the polyimide film.
    Type: Grant
    Filed: June 4, 1993
    Date of Patent: September 6, 1994
    Assignee: The University of Akron
    Inventors: Frank W. Harris, Stephen Z. D. Cheng