Patent GB-733472-A (GB)
Title: Transfer sheet and method of making same
IPC: B41M5/04
Filed: 1950-01-02
Abstract: 733,472. Hectograph carbon papers. COLUMBIA RIBBON & CARBON MANUFACTURING CO., Inc. Jan. 21, 1950 [March 30, 1949], No. 29707/49. Class 100 (4). A hectograph carbon paper comprises a foundation sheet with a pressureresponsive transfer coating including a soluble dye e.g. crystal violet, methyl violet, brilliant green, magenta and a dye-carrying vehicle predominantly of waxy material, and a protective coating which includes a layer in which wax predominates, the transfer coating having substantially constant colour concentration throughout its thickness. In one form, in order to prevent the commingling of the dye between the waxy transfer coating and a waxy protective layer which would result in decreased colour concentration near the surface of the transfer coating and thus produce poor copies, the material of the layer is first reduced to liquid form either by melting or dissolving in a volatile solvent, and is then sprayed on to the transfer coating under cooling or evaporating conditions, so that the material reaches the transfer coating in the form of minute particles which are cool or free of solvent and thus do not absorb colour from the coating. The layer is subsequently buffed. In another form, Fig. 5, the transfer layer 41 is coated with a very thin barrier layer 43 predominantly of wax or waxy material dissolved in a volatile solvent which is ineffective against the dye, and may include a synthetic resin, e.g. chlorinated rubber, as a toughening agent. Suitable solvents are carbon tetrachloride, solvent naphtha and trichlorethylene. A further coating 42 of waxy material is spread on the layer 43, the latter providing an insulating layer which prevents commingling of the dye between the layers 41, 42. The layers 42, 43 are not more than 0.0002 and 0.0001 inch respectively in thickness, and their combined thickness may not exceed 0.0002 inch. In a modification, the intermediate layer 43 is cast using a resin or a cellulosic material in place of waxy material and may be 0.00005 inch or less in thickness. Examples given are (1) polyvinyl acetate 2 parts by weight, trichlorethylene 143 parts, " Santiciser " (Registered Trade Mark)  part; (2) ethyl cellulose 1 part, carbon tetrachloride 158 parts. In a further form, Fig. 6, the transfer layer 51 is coated with a layer 52 basically of wax or waxy material and containing a high percentage of a dye material which is insoluble in water but soluble in spirit such as alcohol. Commingling of the dyes takes place at the interface A but produces a mixture having substantially the same colour concentration as the original transfer layer ; transfer of colour to an operator's hands does not occur as the dye in the layer 52 is water-insoluble. Dye bases, particularly those of the triphenyl methane-diphenyl methane groups, are suitable for incorporation in the layer 52. An additional coating of waxy material may be placed on the layer 52 which could then be made thinner. Metallic lamelliform particles may be incorporated in the protective coating in a layer other than that in direct contact with the transfer layer. A hectograph carbon sheet made as described may form one leaf of a folded sheet, the other leaf of which is adapted to be used as a master when detached after being inscribed as desired in a typewriter or otherwise. . According to the Specification as open to inspection under Section 91, the protective coating could be applied to transfer papers other than hectograph carbons, and metallic lamelliform particles could be incorporated in the layer adjacent to the transfer layer. This subject-matter does not appear in the Specification as accepted. Reference has been directed by the Comptroller to Specification 669,212.