GB399269A - Improvements in or relating to the formation of relief images for photographic and other purposes - Google Patents

Abstract

The method of forming a colloid relief image described in the parent Specification is modified by employing two supports, one of which may be a film or paper bearing a layer containing a reducible light-sensitive compound, and the other a film, paper, glass, linoleum, metal &c. bearing a layer containing the colloid and an organic acid or a salt thereof, exposing the first layer to light to produce a latent image, bringing it into damp contact with the second layer in order to produce by chemical contact action a latent image in that layer, and heating the second layer for example to 90-130 DEG C., before or after removal of the first layer, to develop in the colloid a relief corresponding to the image. Alternatively the first layer may contain also an organic acid or a salt thereof, and the second layer may contain also a light-sensitive metal compound, in which case both layers are exposed to light to produce a latent image, whereafter they are placed in contact so that the image in the first layer may reinforce, by chemical contact action, that in the second layer. The second layer may contain acid sodium phosphate in addition to the organic acid or salt. As light-sensitive compounds are instanced salts of heavy metals such as ferric ammonium citrate or oxalate, ferric chloride or sulphate, potassium ferricyanide or mercuric or mercurous nitrate, chloride or sulphate, and it is stated that ordinary ferroprussiate paper will serve as the first layer. As organic compounds are instanced soluble carboxylic acids such as oxalic, citric, tartaric, formic, malic or lactic acid, or salts thereof. Reference is made to the addition of borax to the relief-forming layer to increase the hardness of the relief. Three particular examples of compositions and processes are described. It is stated that the relief may be used in any of the ways referred to in the parent Specification, e.g. as printing surfaces, moulds, for making stereo or electro plates, decorative papers, ornamental reliefs by colouring and varnishing, paper for cheques, and for Braille work.