GB1400791A - Photographic dye-forming processes and silver halide products - Google Patents

Abstract

1400791 Photographic dye-forming process POLAROID CORP 20 June 1972 [21 June 1971] 28796/72 Heading G2C A photo-sensitive element comprising exposed silver halide, which may be an emulsion layer, is developed with aqueous alkaline processing composition in the presence of a compound that will react imagewise upon development to liberate first or second reagents to form an imagewise distribution of at least one of the first and second reagents, the first reagent containing an aldehyde or ketone group and the second reagent being capable of reacting with the aldehyde or ketone group of the first reagent to form a dye, and the first and second reagents are then reacted to form a dye image. The photo-sensitive element may have a sheet, which may comprise an imagereceiving layer, attached to its support and overlying or capable of overlying the silver halide emulsion. The material may comprise a processing composition or the components thereof capable of being spread as a layer between the silver halide emulsion and the sheet. The composition may be an aqueous alkaline solution containing silver halide solvent and developing agent. The process may involve diffusion of a soluble silver complex imagewise to a layer containing a compound which will liberate the first reagent in the presence of the complex and reaction of this first reagent with the second reagent in the same layer to produce a non-diffusible dye image, see Fig. 1 (not shown). Alternatively, the imagewise distribution of soluble silver complex may diffuse to a material comprising a layer the compound which will liberate the first reagent in the presence of the complex and also contains the second reagent, followed by reaction of the two reagents to form a dye image, see Fig. 2 (not shown and examples). The compound may contain the group -S-X- #N- or -S-X-N= where X is -#C-, -#C=#C-#C-, and may be a thiazolidine or benzothiazoline e.g. 2-(p-dimethylaminophenyl)-3 -propylthiazolidine (Ex 1 to 4) or bis-(N-butylthiazolidin- 2-yl) methane (Ex 5). The second reagent may be be a methylene coupler e.g. malononitrile (Ex 1), N-ethyloxindole (Ex 2), α-cyanoacetanilide (Ex 3), N-methyl-α-picolinium tosylate (Ex 4), 1,3-dimethylthio-barbituric acid (Ex 5) or another methylene coupler selected from a list of 40 disclosed. The second reagent may be another colour former e.g. a hydrazine derivative such as 2,4-dinitrophenylhydrazine.