GB1073999A — Process for forming stable images in photochromic material

USPTO Abstract

1,073,999. Stabilizing photo-chromic images. NATIONAL CASH REGISTER CO. Nov. 12, 1965 [Jan. 29, 1965], No. 48189/65. Heading G2C. Stable photo-chromic images are produced by imagewise exposing a layer containing a spiropyran to produce a temporary image, and before, during or after exposure treating the layer with an acid gas to form an acid complex and converting the complex into an acid-base reaction product by reaction with a basic chromogenic material which is capable of changing colour in the presence of the acid complex to produce a stable image. The photo-chromic layer may contain the chromogenic material or this may be applied in a solution to the layer containing the acid complex. Specified chromogenic materials are N-halophenyl derivatives of leucaurimine, acyl auramines, rhodamine B, lactams, styryl dyes and 4, 4', 4", 4"' (oxydimethylidene)tetrakis (N, N dimethylaniline). Reversed images may be produced by overall exposure to ultraviolet light followed by imagewise exposure to green light when the spiropyran reverts to the uncoloured form followed by treatment with the acid gas (e.g. sulphur dioxide, boron trichloride or iodine) and the chromogenic material. The background areas of the exposed material may be fixed by washing out the spiropyran with a solvent. Reference has been directed by the Comptroller to the Specifications 1, 30, 217 and 1, 030, 219.