IE41184L - Sheet material comprising an antistatic agent - Google Patents

Abstract

1456885 Anti-static coatings WIGGINS TEAPE Ltd 16 July 1975 [31 July 1974] 33741/74 Heading B2E Sheet material, having a synthetic polymeric surface, is coated with an antistatic agent comprising a synthetic hectorite clay having a layered structure wherein the layers carry an electric charge. The sheet material may be a paper material or a heat-consolidated web comprising or consisting of fibres of synthetic polymer. The material is coated on one or both surfaces with a layer of synthetic polymer e.g. polyethylene, and is for use as a substrate for receiving a radiation-sensitive coating for photographic purposes. The antistatic agent comprises synthetic hectorite day, being a compound having a magnesium silicate lattice structure containing magnesium ions bound to hydroxyl ions, some of which may be replaced 'by fluoride. Some of the magnesium ions are replaced by lithium ions or are absent from the lattice structure and/or some silicon atoms are replaced by e.g. Al, Sn, Zn or Ti atoms, which causes the formation of an electrically charged layer structure; in the presence of water exchangeable sodium ions disposed between the layers and balancing the charges on the layers, become hydrated, leaving charged layers which repel each other so that the hectorite clay forms a colloidal sol in the water. The antistatic agent may be present in a size coating on the paper base, under the polymeric material layer, or may be a backcoat on the polymer-coated sheet. Alternatively, the antistatic agent may be a coating over the polymeric coating. The antistatic coating may include sodium sulphate, a binder such as carboxymethylcellulose, starch or gelatine, colloidal or particulate silica, and a wetting agent. When applied over the polymer surface, the latter is preferably first subjected to a corona discharge treatment to promote adhesion of the antistatic agent. The antistatic composition is applied as an aqueous colloidal solution, subsequently dried. The polymer layer may be applied by extrusion coating. The treated base may be given a further coat of conventional radiation (light)-sensitive emulsion of gelatine containing selenium sulphide, zinc sulphide or cadmium sulphide (if necessary for adhesion, after application of a suitable sub-coat), to give a sheet material for use in chemical transfer photographic processes. [GB1456885A]