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Ascorbic Acid Developing Compositions

IP.com Disclosure Number: IPCOM000004576D
Publication Date: 2001-Feb-22

Publishing Venue

The IP.com Prior Art Database


"Black and white silver halide photographic developing compositions are provided, which comprise: (a) a developing agent of the ascorbic acid type; and (b) an auxiliary developing agent of the 3-pyrazolidone type having solubilizing groups. The composition also contains usual componets such as antifoggants, sequestrants, sulfites, buffers. Such compositions can be used for developing silver halide X-ray films or Graphic Arts films."

This text was extracted from a WORD97 document.
This is the abbreviated version, containing approximately 15% of the total text.

Ascorbic Acid Developing Compositions

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 yield a developed photographic image. Many useful developing agents are known in the art, with hydroquinone and similar dihydroxybenzene compounds and ascorbic acid (and derivatives) being some of the most common.

Dihydroxybenzenes (such as hydroquinone) are the most common black-and-white developing agents and are quite active to provide development in various black-and-white photographic elements with or without booster and nucleating compounds. However, they are disadvantageous from several considerations. For example, hydroquinone compositions are not completely stable in air, being prone to aerial oxidation. The by-products from instability are often insoluble, black and tarry materials that contaminate the processing solutions and equipment. The oxidation of hydroquinones also leads to higher pH that in turn leads to increased developer activity. Images can be produced faster so the processing time must be reduced. The net effect is less control of the process, and less desirable sensitometric properties in the processed materials.

Another class of black-and-white developing agents comprise ascorbic acid and its various derivatives, for example as described in US-A-5,236,816 (Purol et al). Developing compositions containing ascorbic acid generally place less oxygen demand on the environment, are more environmentally friendlier.

Most developing solutions are formulated as concentrated liquid solutions, or as a powders or agglomerates. The user must dilute concentrated liquid solutions with water to produce the working strength. Such solutions cannot be concentrated significantly, because of the various components therein, without the use of auxiliary solvents that are preferably to be avoided.

The user must dissove the powder composition in the proper amount of water to provide a developer solution. In practice, the powder composition is preferably readily soluble in water at ambient temperature and does not require heating to effect complete dissolution. The higher temperature increases aerial oxidation of the developing agent and formation of undesirable by-products. Moreover, this is quite time consuming for the heating and subsequent cooling of the solutions. There is a desire to be able to formulate developer compositions in either dry or aqueous form while avoiding the problems noted above. It would also be preferable to minimize packaging, and to improve the solubility characteristics of the individual developer components.

An improved black-and-white photographic developing composition comprises:

a) an ascorbic acid developing agent, and

b) an auxiliary co-developing agent of the 1-phenyl-3-pyrazoli...