| 摘要 |
<p>Transcriptive sheet material that can produce on an underlying surface a positive copy of writing received on an upper surface comprises a carrier of flexible sheet material having on at least part of one surface a colour layer and a top layer covering the colour layer. The colour layer consists essentially of a mixture of a coloured pigment and a binding agent of high molecular weight and free from waxy, oily and fatty components. The top layer consists essentially of a saturated aliphatic carboxylic acid which has a molecular weight of from 1000 to 20,000 and an acid number of from 10 to 150, and in which the terminal groups of the main chain of carbon atoms are free from carboxyl groups, and the carboxyl groups are bound either directly to the main chain or to aliphatic side chains having from 1 to 4 carbon atoms. The carrier may be of paper, woven or non-woven cellulosic fibrous material or a foil or film of a synthetic polymer. The sheet material may be made by: (a) coating at least a portion of one surface of the carrier with a solution of the mixture of pigment and binding agent, e.g. polyvinyl acetate, in a volatile solvent; (b) drying the layer so formed; (c) applying to the dried layer an aqueous dispersion or solution of the polycarboxylic acid; and (d) drying this last-applied layer at a temperature below the fusion point of the polycarboxylic acid. The polycarboxylic acids may be made by the oxidation of branched polyethylenes or polypropylenes or by the copolymerization of ethylene and propylene with unsaturated mono- or di-carboxylic acids. A proportion of the carboxyl groups may be esterified with an alkanol, a polyalkoxyalkanol, or a hydroxypolyalkoxyalkanol to leave a terminal hydroxyl group on the alcohol moiety of the esterified groups. The polycarboxylic acid may be mixed in the aqueous dispersion with a water-dispersible polymer that may be a copolymer of vinyl chloride and acrylic acid, a copolymer of vinyl chloride, acrylic acid and a vinyl ester, a polymer of an acrylic acid ester, an acrylamide polymer having free carboxyl groups, a polymer of methacrylic acid or of an ester thereof, or a montan wax containing carboxyl groups or esterified carboxyl groups. A plurality of sheets or endless webs according to the invention may be superposed and fastened together or folded zig-zag to form a writing pad. Reference has been directed by the Comptroller to Specification 956,767.</p> |
