Patent GB-740166-A (GB)
Title: Photographic process for the production of a pigment image on a receiving surface and light-sensitive sheets for use therein
IPC: G03F7/115
Filed: 1953-02-19
Abstract: 740,166. Photographic transfer process. CHEMISCHE FABRIEK L. VAN DER GRINTEN N.V. Feb. 19, 1953 [April 1, 1952], No. 4701/53. Drawings to Specification. Class 98 (2). A pigment image is formed on a receiving support by exposing in the manner of screen reflectography a light-sensitive sheet comprising a light-pervious support having distributed over one side a light-sensitive material the adhesive power of which is changeable -by light and a reflectographic light screen, the lightimpervious parts of which comprise pigment matter; pressing the image side of the exposed sheet against the receiving surface under conditions selectively rendering portions of the sheet in the exposed or unexposed areas more adhesive to the receiving surface than the remaining part of said sheet, and separating the surfaces whereby the more adhesive portions of the light-sensitive sheet together with pigment matter of the corresponding screen areas are transferred to the receiving surface. The transfer is preferably carried out in the presence of a liquid which may be applied to either or both the image and receiving surfaces. The light-sensitive sheet may comprise a lightpervious support one side of which carries the light-sensitive layer over which the screen is formed, or the screen may be applied direct to the support and then covered with the lightsensitive layer. Methods of making such sheets are described in which the screen parts are taken over by the support (with or without lightsensitive layer) from a screen matrix. Both types may be combined to give a sheet comprising a support, light-sensitive layer, screen, and a second light-sensitive layer in that order. Any of the above arrangements can be used with a support or light-sensitive coating having cavities impressed in it in which the screen parts are located. The light-sensitive layer may be first applied and then the cavities filled with pigment matter, or the cavities in the support first filled with pigment and then the whole coated over with a light-sensitive layer. The light-sensitive material may also be mixed with the pigment in the screen parts, which again may be located. in cavities in the support. The screen parts may take the form of circular islands of opaque pigment surrounded by lightpervious areas, or of light-pervious areas in the form of circular islands surrounded by opaque pigment matter. The light-sensitive material may be one whose adhesive properties and/or power of swelling in water are affected directly by light or by the action of light followed by some after-treatment as in the bichromatecolloid system of Specification 296,008, [Class 98 (ii)]. Suitable light-sensitive materials are bichromates in general, a mixture of a ferric compound, tartaric acid and gum arabic, auramin, erythrosin, diazo-compounds, azidostyryl-ketones and azido-styryl azides. The light-sensitive material may be applied by impregnation from a suitable solution but it is preferred to apply them as a layer, using a lyophilic binding agent such as gelatine, gum arabic, proteins, fish-glue, agar-agar, dextrin, casein, gum-tragacanth, methyl cellulose, shellac, colophony, asphalt, synthetic resins and polyvinyl alcohol. The screen parts are preferably hydrophobic and porous. Suitable pigments are soot, graphite, carbon black, ochre, white-lead, baryta, titanium dioxide, ironoxide, Hansa Gelb 10G, and Lithol echtscharlach R.N. pulver. They are preferably mixed with a binder such as asphalt, gelatine, gum, synthetic polymers, cellulose or its derivatives such as the acetate-butyrate, proteins, casein, and drying oils, and dispersed in solvents such as xylene, propylene glycol, glycerol and ethyl acetate. The support for the light-sensitive sheet is preferably hydrophilic and may be tracing paper, polyvinyl acetate, celluloid, " Cellophane " (Registered Trade Mark), cellulose acetate or partially or completely deacylated cellulose esters. The receiving sheet may be paper, transparent paper, artificial resins, metal, glass or a ceramic surface. The transfer is aided by the use of adhesives either on the surface of the receiving sheet or in the transfer liquid. Thus the receiving surface may be coated with gelatine, polyvinyl alcohol, casein or an artificial resin emulsion, or the transfer liquid may contain gum arabic, polyvinyl alcohol, dextrin or fish glue. The transfer liquid may be ethyl acetate, acetone, pure water, or water containing alcohol, or wetting- agents. The transfer is assisted by pressure, and the wetting of the surfaces and' pressing together of the sheets may be carried out in one operation, a suitable apparatus being described. Heat may also assist the transfer, and to this end the rollers between which the sheets are pressed may be heated. Depending on the lightsensitive sheet, the receiving surface and the conditions of transfer, a positive or negative transfer image may be obtained. Under certain conditions all the transferable areas may be transferred to leave a good remnant image, while under other conditions only part of the transferable areas may be transferred, in which case further transfers may be obtained until the transferable pigment is exhausted. Multicolour images may be obtained by transferring images from sheets having different pigments on to one receiving surface in register. The exposure of the light-sensitive sheet is by the reflex process, and the order of the layers in the direction of the incident light is always screen, light-sensitive material and original. In the examples, the light-sensitive material is generally " diazo aldehyde " which is the condensation product of p-diazo diphenylamine and formaldehyde, as described in example I of Specification 418,011. In other examples, the light-sensitive material is ammonium bichromate, 4,4<SP>1</SP> - diazidostilbene - 2,2<SP>1</SP> - disoditun sulphonate, p - aminobenzene diazonium borofluoride, p - N - ethyl - N - # - hydroxyethylamino benzene diazonium chloride zinc chloride double salt, and the corresponding N-ethyl- and N-N-diethyl-compounds. In example I a cellulose acetate sheet is coated with a solution of gum arabic, gelatine, diazo-aldehyde and water and then moistened with a solution of diazoaldehyde, ethyl alcohol and water in order to make it adhesive. It is then pressed against the surface of a cylinder which comprises deacylated cellulose acetate formed with an intaglio screen relief the depressions of which have been filled with a composition comprising carbon black, asphalt and xylene. The screen parts are thus taken over from the cylinder by the sensitized sheet. The sheet is exposed to an original in the manner of screen reflectography and transfer is effected on to a sheet of transparent paper having its receiving side coated with gelatine, by dipping both sheets in. water and pressing them together at room temperatures by means of rollers under a lineal pressure of 2 kg./cm. The transfer image is a transparent positive and the remnant image a transparent negative, transfer being almost complete. Many other examples are given. Specifications 401,898, 425,126, 510,233, 544,882, 614,155, 626,501, 630,874, 645,211, 655,274, 655,275, 740,165, U.S.A. Specification 1,618,505 and Dutch Specification 59,407 also are referred to.