ES360749A1 - Method of reproducing an image using a diazotype film - Google Patents

Abstract

A photographic process comprises imagewise exposing a diazotype material having a linear latitude greater than 0.7 (linear latitude being defined as the extent of the linear portion of the H and D curve on the log E scale, the linear portion being that portion at which there is no more than a 20% deviation from the average slope of the linear portion) and developing using an alkaline gas at a pressure greater than atmospheric the diazotype material comprising a support and a layer containing a diazonium compound and two couplers with different coupling rates, the ratio C, of the molar concentration of the faster coupler to the molar concentration of the diazonium compound(s) being less than 1:1 and more than 0 2:1 and the ratio of C 1 K 1 to C 2 K 2 being at least 5:1, where K 1 and K 2 are the coupling rates of the faster and slower couplers respectively and C 2 is the ratio of the molar concentration of the slower coupler to that of the diazonium compound(s). Specified faster couplers are dihydroxynaphthalenes, pyronones and 2-hydroxy-3-naphthoic acid amides. Specified slower couplers are phenols, and resorcinol ethers. In the examples, the light-sensitive solutions are applied to a cellulose ester support with ratio C, being greater than 1:1 as the diazonium compound is more slowly imbibed than the coupler because of its greater size. Thus the dried materials have the correct ratio C, and give linear latitudes of 0À82 to 1.55 on development. The light-sensitive solution preferably contains two diazonium compounds and optionally contains benzamide or an ultraviolet absorber such as thienyl-2-vinyl thienyl sulphone. Alternatively, a cellulose ester may be added to the light-sensitive solution and the solution then coated on a polyester support the ratio C, for this solution being within the specified limits.