GB883557A - Improvements in or relating to methods of making hectographic copies - Google Patents

Abstract

883,557. Hectographic transfer paper &c. RITZERFELD, W., and RITZERFELD, G. April 8, 1959 [April 19, 1958; Sept 24, 1958 (3); Nov. 6, 1958], No. 11866/59. Class 96. [Also in Group XVI] A method of making hectographic copies from a printing master sheet prepared photomechanically or by inscribing and having printing image areas which comprise a non- staining or only slightly staining leuco dye compound, comprises, prior to the printing process, converting the leuco compound into its alcohol or water-soluble heavily coloured dye salt by the action of an acid, subjecting it to an oxidization process before, with or after the acid treatment and duplicating on to copy sheets moistened with a neutral-reacting copying liquid forming a solvent for the dye salt. Leuco compounds of a triphenyl-methane dye may be used. On photo-mechanically prepared master sheets, the leuco compound and optionally the oxidation medium are contained in a gelatin layer containing a silver halide. An example of a developing liquid is: water 1000 c.c., pyrochatecol 15 gms., sodium sulphite 1.5 gms., potassium carbonate 60 gms., further diluted 1 to 3 in water. In the case of inscribed master sheets, parts of a layer of fat, waxes, leuco compound and oxidation medium is transferred by hand or typewriter pressure to the master sheet from a transfer sheet in contact therewith. The transfer layer may comprise leuco base of methyl violet 50 parts, barium peroxide, potassium dichromate or sodium peroxide 5 parts; petroleum jelly 35 parts; carnauba wax 10 parts. The leuco base of malachite green may be used. The acid, e.g. formic acid may be applied as a vapour, or as a liquid, such as a 20% aqueous solution of hydroxy carbolic acid (glycolic acid or lactic acid) with 4% of formic acid, a 50% solution of acetic acid with 4% of formic acid, a 5% solution of formic acid, or acid-reacting substances, such as saturated aqueous solution of substituted phenols, aromatic carboxyl acid or naphthols, e.g. p-nitrophenol, picric acid, salicylic acid, or α-nitronaphthol, to which substances may be added, e.g. formic acid, acetic acid, salicyclic acid, lactic acid, hydrochloric acid, phosphoric acid, nitric acid, sulphuric acid or glycolic acid; or as a solid, in a watersoluble binder in a colloid or methyl cellulose as a layer on a contact sheet, e.g. amino acid and manganese dioxide or lead dioxide suspended in gum arabic, polyvinyl alcohols or methyl cellulose, the oxidizing substance in this case being contained in the same layer. Otherwise the oxidizing substances may be applied in a bath, e.g. water 1,000 c.c., permanganate 30 gm., potassium dichromate 30 gm. ; oxidizing substances which avoid discolouring the master sheet are, e.g. benzoyl peroxide. The copying liquid is alcohol, water or a mixture thereof, to which a higher valency alcohol may be added to increase the dissolving power.