Curl-resistant pressure-sensitive transfer sheets and method

摘要

Compositions used in making pressure-sensitive transfer sheets (see Division D2) comprise: (Example 1) vinyl chloride-acetate copolymer, polystyrene, alkali blue, gas black, milori blue, phthalocyanine blue, castor oil, mineral oil, naphthol and solvents; (Example 2) vinyl chloride-acetate copolymer, collodion cotton, gas black, milori blue, phthalocyanine blue, castor oil, naphthol, and methyl ethyl ketone and methanol; (Examples 3 and 4) similar butadiene-styrene copolymer instead of collodion; (Example 5) vinyl chloride-acetate copolymer, polystyrene, magnetic iron oxide, dehydrated castor oil, mineral oil and methyl ethyl ketone; the two oils of this last composition can be replaced by blown castor oil; and (Example 6) similar to Example 5 but containing also a phthalocyanine pigment and castor oil.ALSO:A curl-resistant pressure-sensitive transfer sheet comprises a flexible foundation and a microporous spongy ink-releasing layer of a solid binder material having dispersed therein a pressure-releasable ink comprising oil and colouring matter. The binder material is a combination of two materials that are not soluble in one another in the proportions used. One is a vinyl resin and the other is another resinous or a cellulosic film-forming binder, and is used in amount sufficient to render the sheet curl-resistant. The vinyl resin may be a copolymer of vinyl chloride and vinyl acetate; the other binder may be polystyrene, collodion cotton, ethylcellulose or a butadiene-styrene copolymer. The flexible foundation may be of paper or foil. The oil may be a mixture of castor oil and mineral oil, castor oil alone, dehydrated castor oil and mineral oil or blown castor oil. The pigment may be a mixture of gas black, milori blue and phthalocyanine blue, with or without alkali blue, or magnetic iron oxide with or without phthalocyanine blue. The coating may also contain a small proportion of naphthol. The oil, pigments and naphthol (if any) may first be pulverized in a mill and then mixed in a stirring apparatus with solutions of the binders. The mixture is then coated on to the foundation sheet.