Patent GB-740165-A (GB)
Title: Process for the production of a pigment image upon a receiving surface by means of another surface carrying a light sensitive material and pigment matter, and a pigment sheet for use in this process
IPC: G03C5/20
Filed: 1953-02-19
Abstract: 740,165. Diazotype transfer process. CHEMISCHE FABRIEK L. VAN DER GRINTEN N.V. Feb. 19, 1953 [April 1, 1952], No. 4700/53. Drawings to Specification. Class 98 (2). A process for the production of a pigment image on a receiving support comprises imagewise exposing a pigment sheet containing a light-sensitive diazo compound, azido-styrylketone or azido-styryl-aryl-azide, and pigment matter, said light-sensitive material being such that its adhesive power is altered on exposure to effect a difference in transferability of the pigment between exposed and non-exposed portions, pressing the exposed surface against the receiving surface in the presence of an aqueous liquid so that in the transferable portions pigment is transferred to the receiving surface, whilst in the non-transferable portions the pigment remains on the original sheet, and finally separating the surfaces. The transfer is affected by the presence of binders in the pigment sheet, the nature and amount of the transfer liquid, the receiving support and the temperature and pressure during transfer, and by varying these conditions, either positive or negative transfers can be obtained. Under certain conditions all the transferable pigment transfers and leaves a good remnant image on the original pigment sheet, whilst under other conditions only a portion of the transferable pigment transfers, and the process may be repeated to give a number of transfer images. Not all diazo-type compounds are suitable for the process of the invention and the suitability of a particular compound under given conditions is found by trial. Various constructions of pigment sheet are given. The support, which is preferably light pervious, may carry the light-sensitive layer and then the pigment layer, or it may carry the pigment layer and then the lightsensitive layer. In the latter case an intaglio surface may be provided on the support and the depressions filled with pigment, but in either case the support may first be covered with a sublayer before the pigment is applied. Such a sublayer may itself be light-sensitive so that the sheet may be exposed from either side, even if the pigment is impervious to light. In another form of pigment sheet the light-sensitive compound and pigment are mixed together and coated on a support. The pigment sheets can be double-sided if desired. It is preferred to use a binder in the light-sensitive layer such as gelatine, gum arabic, proteins, fish glue, agaragar, dextrin, casein, gum tragacanth, methyl cellulose, hydrophilic artificial resins and polyvinyl compounds, and such a binder is preferably hydrophilic. When the pigment is not mixed with the light-sensitive material binding agents such as Syrian asphalt, synthetic polymers and cellulose derivatives are preferably added. The pigment is preferably hydrophobic and porous to water. Suitable pigments are Heliogene Blue B, Lithor Echt-Scharlach R.N. Pulver, Crystal Violet, Hansa Yellow 10G, soot, carbon black, graphite, ochre, white lead, baryta, titanium dioxide and iron oxide. It is preferred to apply the pigment layer to a hydrophilic surface (either the support itself or a sublayer) such as partially or completely deacetylated cellulose acetate. The transfer liquid may be pure water or water containing acid, alkali, wetting-agents, alcohols or other liquids. It may be applied to either or both the pigment and receiving sheets, and the application of liquid and pressing the sheets together may be combined in one operation. A suitable apparatus is described for this purpose. The receiving support may be glossy book paper, transparent paper, films, textiles, glass, rubber or metal. Additional adhesives are of use in the transfer and these may be added to the transfer water or located on the transfer side of the pigment sheet or the receiving side of the receiving sheet as a layer which becomes adhesive on moistening. The pigment layer may be composed of two different pigment layers, the one turned towards the support of the pigment sheet contrasting visually with the receiving sheet, and the one turned away from the support of the pigment sheet contrasting visually with that support. The pigment layers are so coherent that on transfer both or neither are transferred to give different coloured transfer and remnant images. The invention may also be used for the production of multi-colour transfer images by transferring pigments of different colours from their respective pigment sheets in register on to one receiving sheet. The invention is illustrated by a large number of examples wherein both positive and negative transfer images are obtained. In one example a sheet of cellulose acetate has applied to one side a solution of diazoaldehyde (the condensation product of p-diazodiphenylamine and formaldehyde according to Example I of Specification 418,011), water and ethyl alcohol. The layer is dried and then overcoated with a composition comprising carbon black, asphalt, xylene and a 10 per cent solution of cellulose acetate butyrate in ethyl acetate and dried again. It was exposed for 30 seconds under an Indian ink line drawing on tracing paper and transferred to a sheet of transparent paper having a layer of gelatine on its receiving surface by immersing both sheets in water for a few seconds and then passing them together at a speed of 2.5 metres per minute through rollers under a lineal pressure of 2 kg. per cm. The transfer image is a transparent positive and the remnant image a transparent negative. The gelatine layer of the receiving support may contain chrome alum. In other examples the pigment layer is applied to paper or cellulose acetate sheet coated with gum arabic and then a layer of diazo aldehyde in gelatine is applied. In further examples the light-sensitive compound is 4-4<SP>1</SP>-diazido-stilbene-disulphonic acid- 2-2<SP>1</SP>, p-aminobenzene diazonium borofluoride, the chlorostannate of 4-4<SP>1</SP>-tetrazodiphenylamine, p - ethylamino benzene diazonium chloride zinc chloride double salt, p-ethyl-#- hydroxyethyl amino benzene diazonium chloride double salt, p-ethyl-#-diethylaminoethyl-amino benzene diazonium chloride zinc chloride double salt, tin chloride double salt of the chloride of 4,4<SP>1</SP> - tetrazo - 2 - 21 - 5 - 51 - tetramethoxy -triphenylmethane, p-cyclohexylamino benzene diazonilun chloride zinc chloride double salt and the sodium salt of 4-azido-#-acetyl styrene sul. phonic acid-2. Specifications 401,898, 510,233, 614,155, 645,211, 655,274, 655,275, 740,166 and U.S.A. Specification 1,618,505 also are referred to.