![]() ![]() The screen making process utilizes a flood curing process where the screen and exposure lamp remain static or stationary. It is easier to achieve proper cure with UV inks because they use a linear curing process where the surface is passed under lamps that extend across the entire surface, providing uniformity of UV exposure in that dimension, while the motion of the substrate provides uniformity of exposure along the direction of travel. Just as screen printers using UV curable inks must make sure UV travels through the inks entire coating thickness to achieve proper cure, so must they make sure UV travels through the emulsions entire coating thickness to achieve proper cure. If, after exposure, an emulsion formulation fails to meet ALL the minimum requirements of acceptability, then it is not cured, or an incorrect emulsion formulation was selected. Minimal performance specifications for emulsions involve chemical and mechanical resistance, as well as copying properties required to reproduce the intended image. ![]() These requirements typically include a minimal performance specification such as a specific hardness target for a hardcoat or shear strength for an adhesive. In general, the reactive resin and photoinitiator in screen printing emulsions are made up of polyvinyl alcohol, acrylic resin, and sensitizer (usually diazo or SBQ) formulated in a base of water and various proprietary additives used to enhance the products performance and stability.Ī UV curable formulation, whether it is an emulsion, ink, or adhesive, is considered cured when it meets the requirements of its intended application. The energy required lies in the UV region of the electromagnetic spectrum and can come from a natural source such as the sun or an artificial source such as metal halide lamps.
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