Patent GB-657764-A (GB)
Title: Production of photographic relief images
Inventor: MARRIAGE ANTHONY
IPC: B22D1/00
Filed: 1948-05-27
Abstract: 657,764. Photographic emulsions. KODAK, Ltd. May 27, 1948, No. 14313. Addition to 581,773. [Class 98 (ii)] A photographic relief image is produced by exposing to an image-forming light a photographic element comprising a layer of an unhardened sensitive silver salt internal-image emulsion, treating the emulsion to render it capable of forming a surface latent image, exposing it through the support to uniform active radiation to which it is sensitive and which is absorbed thereby to a greater extent than the image-forming light, developing the latent image formed by the active radiation, tanning the layer where silver is produced, and removing the untanned colloid of the layer. The first exposure may also be made through the support. The emulsion may be rendered capable of forming a surface latent image by treatment with an ordinary developing solution or a developer of low activity, the developing agent being an organic developer having little or no solvent action on silver halides, and may be a tanning developer used for developing the surface latent image, or, with some emulsions, by treatment with plain water only. The emulsion may have a relatively high silver iodide content and the re-exposure effected with ultra-violet light. A dye or pigment absorbing ultra-violet light may be incorporated in the emulsion during its preparation or by bathing after coating. The emulsion may be dyed with a yellow dye, and the second exposure effected with blue light, or with a red dye and the second exposure effected with green light, or may be dyed with an approximately neutral or brown dye or dye mixture and the second exposure effected with white light. The dye may be incorporated in the bath used for rendering the emulsion capable of forming a surface latent image, and such bath may contain catechol, sodium sulphite, sodium carbonate and dye. A colourless coupling component may be incorporated in the emulsion and a dye formed by treating the emulsion after the first exposure with an alkaline diazonium solution. A proportion of a completely fogged ordinary emulsion (e.g. gelatino-silver chloride emulsion) may be added to the emulsion, the fogged emulsion being developed in the bath for rendering the emulsion capable of forming a surface latent image. Where the first exposure is made through a colour component image, the second exposure may be made through a different colour component image to effect colour correction. The emulsion is finally developed with a tanning developer or with an ordinary developer followed by a bleach-hardening bath, and the unhardened colloid may be finally washed out with hot water. In printing from a colour transparency, the first exposure may be made using a green filter, and the second either using a red filter or and infra-red filter. The second exposure may be unsharp. In example 1, an unhardened internal image type emulsion having a relatively high silver iodide content is dye-sensitized to render it panchromatic and coated on a support, and the resulting material is exposed with red light through the support to a positive colour transparency. The material is treated in a dish with a glass base in an aqueous solution of pyrogallol, metol, and sodium metabisulphite, and is then uniformly exposed through the support to ultra-violet light. The solution is poured off, mixed with aqueous potassium carbonate and bromide, and poured back to effect development. The soluble gelatin is washed out in hot water and the final relief used for imbibition printing. In example 2, material similar to that of example 1 but dye-sensitized to green is exposed with green or blue light to a positive colour transparency, the material is soaked in an aqueous solution of catechol, sodium sulphite, sodium carbonate, and Tartrazine, the material is exposed through the support to violet light, and is developed in a tanning developer, and finally soluble colloid is removed in hot water. In example 3, an internal image type emulsion is mixed with a fogged gelatino-silver chloride emulsion, and after exposure behind a negative is treated in an aqueous solution of catechol, sodium sulphite, and triethanolamine. After exposure through the support, the material is washed, developed in a tanning developer, and soluble colloid removed in hot water. Specifications 581,773 and 635,841 are referred to.