Fine grain silver halide emulsions with polyheteronuclear sensitizing dyes

Claim 1

In a process for increasing the spectral sensitivity of a fine grain silver halide emulsion to monochromatic light emitted from a neon-helium laser, the numerical average grain size of the silver halide of said fine grain silver halide emulsion being not greater than 0.18 micron in diameter or at least 95% by number of the silver halide particles having particle sizes not greater than 0.2 micron in diameter, the improvement comprising adding to said emulsion a sufficient amount of at least one sensitizing dye represented by the following formula (I) ##SPC3## wherein Z 1 represents the group of atoms necessary to form a heterocyclic nucleus selected from the group consisting of a 4,5- diphenyl thiazole nucleus, a benzothiazole nucleus, benzoselenazole nucleus, a naphtho[2,1-d]thiazole nucleus, and a 2-quinoline nucleus, said benzothiazole or benzoselenazole nucleus being substituted by at least one alkoxy group; R and R 1 each represents a lower alkyl group, a hydroxyalkyl group, an alkoxyalkyl group, an acetoxyalkyl group, a carboxyalkyl group, a sulfoalkyl group, an aralkyl group, or an allyl group; R 2 represents an alkyl group, a carboxyalkyl group, a sulfoalkyl group or an aryl group; R 3 represents a hydrogen atom, a lower alkyl group or a carboxyaryl group; X represents an anion; and p represents 0 or 1, p being 0 when the compound forms an inner salt; or represented by the following formula: