| 摘要 |
1324971 Stencils GESTETNER Ltd 4 Jan 1972 [4 Jan 1971] 310/71 Heading B6C A stencil blank, adapted to be cut by an electric stylus comprises two adjacent thermoplastic layers, each having electrically conductive particles dispersed in it, one of the layers being ink-impervious having a higher electrical resistance than the other and having semiconductor particles also dispersed in it. The electrically conductive particles may be of carbon, and the semi-conductor particles of silicon, germanium, cuprous oxide, cadmium sulphide, cadmium selenide or indium oxide. The thermoplastic layers may comprise polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl formal, a vinyl chloride/ vinyl acetate copolymer or a mixture of any of these. The layer of higher resistance may be impregnated into a layer of stencil tissue, and may comprise plasticized nitrocellulose or cellulose acetate propionate (in place of a vinyl resin), the other layer being either coated upon it or upon the face of an adjacent backing paper. The layer of higher resistance may be built up from multiple sub-layers, and its surface may be given a grey colour by addition of titanium dioxide, zinc oxide, zinc sulphide or mixtures thereof. |
