Double exposure method of photoprinting with liquid photopolymers

The method of producting polymerized patterns in photopolymer layers disposed on a substrate by photoexposure with actinic radiation, comprising the steps of:

• disposing on a substrate with an outer surface disposed for photoexposure a layer of photopolymer having the property of polymerizing in the presence of actinic radiation energy with different radiation energy quantities required to polymerize the layer when the surface is contacted with different media,
• radiating the layer through an off-contact phototool image pattern with a controlled amount of radiation energy to polymerize the layer through only a portion of its thickness with a first polymerization step in the presence of a gaseous medium on the layer surface that reduces oxygen inhibition of polymerization in contact with the outer surface of the layer, thereby to produce two patterned areas of polymer defined by the image pattern respectively with polymerized polymer through only a surface stratum part of the layer thickness and unpolymerized polymer through the entire layer thickness,
• replacing the first medium with air as a second gaseous medium in contact with the layer surface to inhibit the polymerization throughout the layer thickness in the presence of radiation where the surface is unpolymerized, and
• then radiating the layer with a predetermined amount of unpatterned radiation energy thereby to polymerize the photopolymer layer in the surface stratum polymerized areas through the thickness of the layer and to prevent substantial polymerization in the area of unpolymerized polymer through the entire thickness, whereby the polymerized surface stratum area serves as a surrogate in-situ phototool for this radiating step.