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Abstract

Several techniques may be used for forming a colored interference filter coating on a substrate such as polyester film. The interference filter has two metal reflective films, at least one of which is semi-transparent. A layer of transparent acrylate polymer dielectric between the metal layers completes the interference filter, which may be sandwiched between protective layers. The dielectric is formed by evaporating an acrylate monomer having a molecular weight in the range of from 150 to 600. Preferably the acrylate monomer has a molecular weight to acrylate group ratio in the range of from 150 to 400. The acrylate condenses on the substrate and is polymerized in situ for forming a monolithic film with a sufficient thickness to produce an interference color. In several embodiments different areas of the film have different thicknesses for producing different interference colors. The thickness of the dielectric can be controlled by the amount of monomer condensed, by either controlling the temperature of the condensation surface or controlling the amount of monomer evaporated adjacent a predetermined area of the substrate. Thickness may also be controlled by condensing a uniform layer of monomer and polymerizing the monomer to different degrees for varying the shrinkage of the film and hence the thickness of the film and color.

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