Patent GB-851384-A (GB)
Title: Process and apparatus for making pigment image records and pigment image records thus made
IPC: G03G15/10
Filed: 1958-02-06
Abstract: 851,384. Photographic processes; photomechanical printing surfaces. CHEMISCHE FABRIEK L. VAN DER GRINTEN N. V. Feb. 6, 1958 [Feb. 6, 1957], No. 3867/58. Class 98(2) Pigment images, which may be used in hectography as printing plates, are produced by exposing a photographic sheet containing an organic light-sensitive compound to yield image portions which (if necessary after processing) have mutually different power for accepting pigment (or a compound which can be treated subsequently to give a pigment or dye), and pressing the exposed image sheet against a solid layer of pigment on a support so that pigment transfers selectively only to those image portions with the greatest power of accepting pigment. The mutually different acceptive power may be brought about by a change in adhesive power of the light-sensitive layer on exposure, or it may be obtained by having rough image portions (which accept pigment) alongside smooth complementary image portions. The latter may be brought about by having a smooth light-sensitive layer on a rough base (or vice versa) and removing image portions by washing-off or transfer, or by having both base and light-sensitive layer smooth, removing image portions and roughening the exposed base by etching, sandblasting or embossing. The transfer of pigment may be brought about by wetting one or both surfaces, e.g. with water alcohol, and in some cases the transfer is assisted by pressure and/or heat. If a suitable pigment such as crystal violet is used, the transferred image may be used in a spirit duplicator. If the "pigment" is a diazonium salt, the transferred image also serves as a printing plate and prints may be obtained by wetting the receiving sheet with a coupler and sodium carbonate, or the coupler and an inhibitor may be included in the pigment sheet and transferred imagewise, in which case the receiving sheet is wetted with sodium carbonate solution. The light-sensitive material may comprise a screen which may be formed in the base, filled with pigment and coated with the light-sensitive layer (see Specification 740,166). After exposure the non-exposed image areas may be washed off to leave the screen as a rough surface which accepts pigment, or the light-sensitive layer and underlying screen may be transferred selectively as in Specification 740,166 to leave the rough screen cavities. The light-sensitive compound may be a diazonium salt, diazo aldehyde, p, pl-diazido-stilbene-o,oldisulphonic acid, a cinnamic acid ester of polyvinyl alcohol, cinnamol malonic acid, or anthraquinone-2; 7-disulphonic acid. These may be dispersed in binders such as gelatin, gum arabic, glue, polyvinyl alcohol, polyvinyl acetate, fish glue, casein or a mixture of gelatin and carboxymethyl cellulose. A rough light-sensitive layer is made by adding kaolin. The base for the lightsensitive layer may be smooth paper, black glazed paper, rubber, brass, matted aluminium, superficially hydrolyzed cellulose acetate, transparent paper, paper coated with cellulose acetate, or regenerated cellulose. The pigment sheet may contain carbon black, zinc oxide, graphite, Bordeaux red, Hansa yellow, vermilion red, Heliogene blue or Syrian asphalt. When the latter is used, the transferred image may be given a heat treatment. The pigment may be mixed with cellulose acetate, butyrate, asphalt, gelatin, gum, cellulose derivatives or casein and coated on matted aluminium, superficially hydrolyzed cellulose acetate, transparent paper or glass. Apparatus is described for coating a support with pigment which dries as it passes to a zone where it is pressed against the image sheet. Figs. 2 and 3 show such apparatus wherein the belt 21 or cylinder is coated with pigment suspended in a liquid 26, the coated belt being dried, if necessary with the aid of air or heat (see Fig. 3) and passed to a zone 28 where it is pressed against the image sheet 34. In Fig. 2 the image sheet is wetted on both sides with transfer liquid while in Fig. 3 the dried pigment layer is wetted before transfer. Any remaining pigment may be removed by a brush 43. Fig. 1 shows a transfer apparatus in which the sheets are inserted into guides 6, 7 and wetted on both sides. The belt 5 passes them to the transfer rollers 3, 4 situated above the liquid 2. Specification 699,085 also is referred to.