HYDROQUINONE FREE DEVELOPERS
Publication Date: 2002-May-17
The IP.com Prior Art Database
Aqueous black-and-white photographic developing solutions are provided, which comprise: (a) an hydroquinone monosulfonic acid or salt thereof (b) one or more auxiliary developing agent of the 3-pyrazolidone type. The black-and-white developing compositions also contain usual components such as inorganic and organic antifoggants, preservatives or antioxidants, buffers, sequestering agents. The B&W compositions can further comprise a silver halide solvent such as a thiocyanante, hardeners such as glutaraldehyde, development restrainers, development accelerators, swelling control agents, sludge control agents and stabilizing agents. The B&W developers can be used for processing industrial radiographic materials.
This disclosure relates to an aqueous photographic developing solution for processing industrial radiographic materials.
The disclosed developers are suitable for processing a film assortment such as described in US 5,965,337. The films described in US 5,965,337 are radiographic films which comprise a support covered on at least one face with a silver halide tabular grain emulsion layer in which tabular grains account for at least 50 percent of total grain projected area and exhibit an aspect ratio of at least 2, preferably between 5 and 25. The volume of the tabular grains is greater than 0.02 mm3, and, advantageously, the grain volume is greater than 0.03 mm3. The tabular grains have a mean grain thickness below 0.5 mm and preferably below 0.2 mm. The tabular grains of the emulsion may be monodisperse or polydisperse, while preferably they are monodisperse. The preferred monodisperse emulsions have a COV less than or equal to 25% and preferably between 10 and 25%. Preferably the tabular silver halide grains are comprised of at least 90 mole % bromide, based on total silver. In preferred forms, these grains contain less than 5 mole % chloride or iodide, based on silver. Iodide can be uniformly or non-uniformly placed in the grains.
Photographic black-and-white developing compositions containing a silver halide black-and-white developing agent are well known in the photographic art for reducing silver halide grains containing a latent image to a developed visible silver photographic image. Many developing agents are known in the art, with hydroquinone being one of the most often in use today. Such compositions can generally contain other components such as auxiliary developing agents, sulfites, buffers, antifoggants, halides and hardeners, etc.
Hydroquinone developing agents are quite active to provide development in various black-and-white elements with or without booster and nucleating compounds. However, they suffer from several restrictions because of technical and environmental considerations. For example, hydroquinone compositions are not completely stable in air, being prone to aerial oxidation. The by-products caused by instability are often insoluble, black and tarry materials that contaminate the processing solutions and equipment. In addition, hydroquinone has become an increasing concern from the point of view of potential toxicity and environmental pollution.
Another class of black-and-white developing agents described in many publications are hydroquinone monosulphonic acid, potassium or sodium hydroquinone monosulphonate. The superadditive effect of hydroquinone monosulphonate with 1-phenyl-3-pyrazolidone (also known as Phenidone) has been reported to be quite large (Mason, Photographic Processing Chemistry, Focal Press, London, 1975, p. 136). Hydroquinone monosulphonate is used in commercial developers today.
The majority of processing machines in common use for industrial radiography are roller tr...