Patents by Inventor Yuh-Loo Chang

Yuh-Loo Chang 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).

  • Patent number: 4863827
    Abstract: A process for forming a multi-level positive working photosensitive element. One forms a composition containing an alkali soluble resin, an o-quinonediazide compound and an in-situ generated acid catalyzed crosslinker in a solvent mixture. After coating on a substrate, drying and partially cross-linking the first layer, a second positive working light sensitive layer is applied. Each light sensitive layer is activated by u.v. radiation in different parts of the spectrum. The top layer is imagewise exposed and developed to form a mask. The second layer is flood exposed through this mask and developed. Each development is conducted with an aqueous alkaline solution.
    Type: Grant
    Filed: October 20, 1986
    Date of Patent: September 5, 1989
    Assignee: American Hoechst Corporation
    Inventors: Sangya Jain, Yuh-Loo Chang