Patent GB-996594-A (GB)
Title: Improvements in or relating to thermographically reproducible hectograph copies and transfer sheets therefor
IPC: B41M5/04
Filed: 1961-07-28
Abstract: Compositions used in making pressure-sensitive transfer sheets (see Division D2) comprise a synthetic resinous or cellulosic film-forming binder, a non-volatile liquid or semi-solid material which does not dissolve nor dissolve in the binder material, a complex azine dyestuff, a volatile liquid that is a solvent for the binder and preferably also for the liquid or semi-solid material, and optionally a conventional spirit-duplicating dye. The compositions used in the Examples are:  (I) ethylcellulose, lard oil, oleic acid, mineral oil, nigrosine, crystal violet, brilliant green and toluene; (II) polyvinyl acetate, mineral oil, lanolin, nigrosine, crystal violet and toluene; (III) chlorinated diphenyl resin, beeswax, induline, Victoria green and carbon tetrachloride; (IV) hydrocarbon polymer, beeswax, methyl violet, aniline black and petroleum naphtha; and (V) rosin-modified alkyd resin, solid polyethylene glycol, crystal violet, nigrocine and petroleum naphtha.  Reference has been directed by the Comptroller to Specification 833,631.ALSO:A pressure-sensitive transfer sheet for use in the spirit-duplicating process comprises a foundation having thereon a frangible layer that is transferable under imaging pressure to a master sheet, and comprises a synthetic resinous or cellulosic films-forming binder which is at least partly soluble in the spirit-duplicating fluids, a non-volatile liquid or semi-solid material which does not dissolve or dissolve in the binder material and a complex azine dyestuff.  The frangible layer may be applied in a volatile liquid that is a solvent for the binder material and preferably also for the liquid or semi-solid material but not for the dyestuff, and is then allowed to evaporate.  The azine dyestuffs absorb infra-red radiation and convert it to heat, so that when the transfer sheet is used to prepare a hectographic master and hectographic copies of this are made, they can in turn be used as "originals" in a thermographic copying process. Azine dyestuffs referred to are rigrosines, indulines, aniline black, N-phenyl-p-phenylene-diamine black, p-aminophenol black and p-phenylenediamine black.  The foundation may be of paper, cellulose acetate or polyethylene terephathalate.  The binder material may be cellulose acetate, cellulose nitrate, ethyl-cellulose, polyacrylamide, polymethacrylamide, polyvinyl acetate, polyvinyl alcohol (partly or completely hydrolysed), polyvinyl methyl ether, polyvinyl ethyl ether, a resin-modified alkyl resin, hydrocarbon copolymers, chlorinated diphenyl, or alcohol-soluble nylon.  The liquid or semi-solid material may be an animal, vegetable or mineral oil, butyl stearate, oleic acid, lanolin, petrolatum, hydro-genated vegetable oil, beesewax or solid polyethylene glycol.  A conventional spirit-duplicating dye may also be present, examples are crystal violet, methyl violet, ethyl violet, chrysoidine, basic or acridine orange, croceine orange, brilliant green, malachite or Victoria green, rhodamine, magenta and safranine.  Reference has been directed by the Comptroller to Specification 833,631.