E.i. Dupont De Nemours and Company

David W Williston

Robert A Covington, Jr

Dale M Hiller

Lewis Clinton Bancroft

Cecil L Long

Process for preparation of conductive circuit utilizing two photohardenable layers on substrate which may contain a conductive circuit, the upper photohardenable layer becoming hardenable and nontacky when exposed to short wavelengths of radiation (ultraviolet) the lower photohardenable layer being tacky and sensitive to long wavelength radiation (visible light). The photohardenable layers are imagewise exposed through a dichromic phototool (black/yellow also having clear areas) and the unhardened image areas are solvent developed revealing tacky areas. The tacky areas are treated with metal or alloy particles or plating catalyst material, and the metallized or catalyzed image is electrolessly plated. Multilayer conductive circuits can be prepared.

Dichromic process for preparation of conductive circuit

Ferromagnetic chromium dioxide is produced in a continuous operation by feeding a preheated paste of hydrated chromium oxides and additives into a twin screw reactor, reacting at elevated temperature and pressure for a short time while venting oxygen and steam, injecting water near the end of the reaction zone to form a viscous chromium dioxide-water mixture, and cooling while passing through a pressure letdown extruder.

Continuous synthesis of chromium dioxide

CrO.sub.2 synthesized by the known hydrothermal reaction of CrO.sub.3 /Cr.sub.2 O.sub.3 /H.sub.2 O mixtures (including minor dopants) by the use of a reaction vessel having a hollow longitudinal core open at both ends. The core may have a cross section of convenient size and shape. This process results in shortened heating and cool/vent/dry cycles resulting in increased overall productivity despite the apparent reduced volume of the reaction vessel.

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Newark, DE, United States of America

David W Williston