Black=and=white silver halide photographic prod. - contg. ballasted reducing agent and developable with basic activator

摘要

An Ag halide photographic prod. which can be developed by a basic activator contains (1) an Ag halide developer, in its free form or as its precursor, in an amt. which is significantly lower than reqd. to reduce the developable Ag halides, and (2) a ballasted reducing agent which is non-diffusible from the layer in which it is incorporated and which partakes in a crossed oxidation reaction with the oxidised developer formed during reduction of the Ag halide to Ag., to thus regenerate the developer in its reduced form; amt. of the ballasted reducing agent is such as to ensure regeneration of the developer to give the reqd. Ag density. The photographic prod. includes radiographic, direct positive and reversal Ag halide emulsion based prods. used in black and white photography. Use of the ballasted reducing agent enables a lower concn. of the developer to be used efficiently. The basic activator does not become rapidly polluted by developers which are released from the photographic prods. Since the developer is incorporated in the photographic prod. itself and not in the basic activator, the latter can be stored for a long time without alteration.