Photographic film having enhanced herschel effect susceptibility and the process using the same

Claim 1

A PHOTOGRAPHIC FILM COMPRISING A BASE AND A LIGHT SENSITIVE SILVER HALIDE EMULSION OF THE TYPE SUITABLE FOR HALF-TONE REPRODUCTION, SAID EMULSION BEING ESSENTIALLY FREE FROM FOG, INSENSITIVE TO LIGHT OF A WAVELENGTH EXCEEDING 600 MU, AND HAVING A GAMMA HIGHER THAN 3.5, SAID SILVER HALIDE BEING SELECTED FROM THE GROUP CONSISTING OF SILVER CHLORIDE, SILVER BROMIDE AND SILVER CHLOROBROMIDE BUT SUBSTANTIALLY FREE OF SILVER IODIDE, AND CONTAINING LESS THAN 1.5 PERCENT OF IODINE BASED ON THE AMOUNT OF SILVER NITRATE USED IN THE PREPARATION OF THE EMULSION, SAID FILM HAVING COATED IN DIRECT CONTACT WITH SAID EMULSION LAYER, A SEPARATE WATER PERMEABLE COLLOIDAL LAYER HAVING UNIFORMLY DISPERSED THEREIN, A DYE WHICH IS KNOWN TO ENHANCE THE HERSCHEL EFFECT IN A CONCENTRATION RANGING FROM 0.15 TO 2.0 MILLIGRAMS PER GRAM OF SILVER NITRATE USED IN THE PREPARATION OF THE CONTACTED EMULSION, AND FROM 10 TO 200 MILLIGRAMS PER LITER OF 0.5 PERCENT OT 10.0 PERCENT AQUEOUS DISPERSION OF THE WATER SOLUBLE COLLOID, SAID DYE BEING SELECTED FROM THE GROUP CONSISTING OF AURAMINE, MALACHITE GREEN, BRILLIANT GREEN, FUCHSINE, IODINE GREEN, NEUTRAL RED, PHENOSAFRANINE, SARANINE, ROSOLANE B, ANILINE VIOLET, DIPHENE BLUE, METHYLENE VIOLET; PINAKRYPTOL GREEN AND PINAKRYPTOL YELLOW.