Abstract: Process for forming a vesicular image utilizing a vesicular recording material having an imaging layer which includes a defined sulphone and/or sulphonamide additive in an amount of 1 to 100% by weight based upon the weight of a polymeric component of the plastics vehicle. The additive provides improved image density and a back-appearing image.

Abstract: Light-sensitive vesicular imaging materials, suitable for the production of colored labels, etc., comprise a light-sensitive vesicular imaging layer applied to one surface of a transparent self-supporting plastics sheet or film such as a linear polyester, e.g. polyethylene terephthalate film, said light-sensitive vesicular imaging layer comprising a polymeric vehicle having uniformly dispersed therein a sensitizing agent which releases a vesicle-forming gas, preferably nitrogen, upon exposure to light and optionally including a pigment or dye, said polymeric vehicle comprising a thermoplastic polymer having a nitrogen permeability constant in the range 1.times.10.sup.-15 to 1.times.10.sup.