Gleitschicht für Thermodruck

摘要

This invention relates to thermal printing, and, in particular, to a coating for preventing sticking of thermal printing materials to a thermal printhead of a thermal printer. In one form of direct thermal printing, colorless forms of heat-activatable dyes are incorporated into a polymeric binder borne on a suitable carrier. Upon application of heat in an imagewide manner, these dyes are converted to their colored forms to form an image in the dye-containing material. Because commonly used polymeric binders are thermoplastic, there is a tendency for them to soften in the heated areas and stick to the thermal printhead, thereby causing malfunctioning of the printing apparatus and reduction in image quality. In thermal transfer printing, the printing process occurs by heat-activated transfer of image-forming material from a donor to a receptor such that the receptor bears the formed image. The construction of the donor requires that the image-forming material be carried upon a thin, flexible backing. The image-forming material may take several forms, such as, for example, a meltable colored wax. Many of the most suitable backing materials are thermoplastic, and therefore have a tendency to soften and stick to the printhead during the thermal imaging process, thereby causing poor print quality and malfunctioning of the printing machine. This invention provides a layer for preventing sticking of thermal image-forming materials to thermal printheads during thermal printing. The layer comprises polymeric material having a non-cyclic, substantially completely saturated hydrocarbon backbone, said backbone having substantially only hydrogen atoms and methyl groups attached to randomly positioned carbon atoms thereon, with no more than one methyl group attached to any one backbone carbon atom. Solubility of the polymeric material in commonly used organic solvents allows very thin layers of the coating to be applied in the form of dilute solutions.