US3523793A - Developers containing silver halide solvents - Google Patents

Description

United States Patent 3,523,793 DEVELOPERS CONTAINING SILVER HALIDE SOLVENTS Vincent J. Miceli, Conklin, N.Y., assignor to GAF Corporation, New York, N .Y., a corporation of Delaware No Drawing. Filed July 3, 1967, Ser. No. 650,603 Int. Cl. G03c 5/30, 5/50, 7/00 U.S. CI. 96-59 2 Claims ABSTRACT OF THE DISCLOSURE First developers for reversal process color development containing high concentration of an alkali metal chlorlde.

This invention relates to photographic developers and particularly to an improved first developer for reversal color processing.

It is known that sulfites are usually added to photo graphic developing solutions for the purpose of preventing oxidation of the developing agent. In addition, it has been observed that the sulfites also have a slight solvent effect on the silver halides and as the development progresses they actually dissolve a small quantity of each silver halide grain thereby minimizing the tendency for clump formation which would increase graininess. This solvent action has been recognized as essential in reversal processes for acceleration of development and the like. In fact, it has been found that a silver halide solvent, in addition to sulfites, is necessary otherwise the development will be so slow that the reversal highlights are not cleaned out and are heavy or dense in the final image.

With the advent of the use of silver halide solvents many problems arose as to the properties of said solvents in satisfying the requirements in negative developers. To be suitable for use, the solvent should accomplish the primary purpose of cleaning out the reversal highlights without dissolving the unexposed silver halide and without the development of fog in the unexposed area of the film. This means that in the ordinary negative development, the silver halide should be completely reduced in the fully exposed areas and the silver halide solvent helps to accomplish this purpose. These solvents should not produce an unusually great amount of latent image growth, that is, they should not develop silver halide to any great extent in the regions surrounding the exposed portions.

Still another characteristic which a silver halide solvent should possess is its ability to promote resolving power and definition and in a color process it should improve the color saturation and brightness of the final image.

Still other elfects which the silver halide solvent should produce are an increase in penetration of the developing agent which is important in the development of multilayer materials, a reduction in grain size, an improvement in resolution at the edges of the image and an increase in the effective reversal speed of the material.

Thus, it is an object of the invention to provide a novel silver halide solvent for photographic developers.

Another object of the invention is the provision of a novel silver halide solvent which effectively restrains fog formation without loss of development speed.

A still further object of this invention is the provision of a novel first developing solution suitable for use in reversal color processing and which provides an increase a in effective reversal speed of the material.

I have discovered that these and other objects of the invention can be readily accomplished by incorporating into photographic developing solutions high concentrations of an alkali metal chloride.

While the mechanism of acceleration is not completely 'ice understood, it is believed that such large amounts of alkali metal chloride in the developing solution increase the solubility of silver halide in the developing solution and thus promotes the physical development of the halide. It also reduces the quantity of silver halide remaining to be developed and consequently increases the effective reversal speed of the material. This acceleration is accomplished without excessive fog formation which is accompanied with the use of most silver halide solvents.

Water to make 1.0 liter.

The following example will serve to illustrate the practice of the invention:

EXAMPLE A reversal color film commercially available under the name GAF Anscochrome film was used for this example. This multilayer color reversible film containing color formers is prepared according to the methods described in U.S. Pats. 2,179,228, 2,179,239, 2,186,849 and 2,220,- 187, and consists of an integral tripack emulsion coated on the usual clear cellulose acetate or nitrate film base. Each of the emulsions is sensitized to one of the primary colors of light, namely, blue, green, and red. The top layer is blue sensitive. A filter layer, yellow in color and blue absorbing, lies under the top layer. Below this filter lies a green sensitive emulsion layer and below this is a red sensitive emulsion layer. Each of the three silver halide emulsion layers contains dye forming compounds which unite during the development of the silver image in an aromatic amino developing agent to form a dye with the oxidation product of the developing agent. This film was imagewise exposed and then developed for 23 minutes at 68 F. with a developer of the following composition:

Ethylenediamine tetra-acetic acid ..grams 0.8 Sodium sulfite do 20.0 Metol (p-methylaminophenol sulfate) do 3.0 Hydroquinone ..do.. 6.0 Sodium bromide do 2.0 Sodium carbonate do 45.0 Potassium iodide milligrams 10.0 Sodium chloride grams 100.00 Water to make 1.0 liter.

The film was washed for five minutes, hardened in an aqueous solution containing an inorganic hardener, e.g., alum, chrome alum, washed, given a second exposure and then developed with N,N -diethyl-p-phenylenediamine color developer. The film is subsequently washed, bleached if necessary, washed and then fixed, washed and dried.

The finished transparency had excellent pictorial qualities and the image was superior to conventionally processed films by showing higher maximum densities in all layers, thus giving the impression of deeper colors in cluding black. This improvement was made possible by reducing the amount of fog produced during the first, negative development, thus leaving more silver halide available in the unexposed areas available for color formation during the second, color-forming development.

Various modifications of the invention will occur to persons skilled in the art. Therefore, it is not intended that the invention be limited in the patent granted except as necessitated by the appended claims.

What is claimed is:

1. In the process of developing a color film of the reversal type which includes the steps of imagewise exposing a film, developing it with a first developing bath for silver halide, re-exposing to light, color developing the same, the improvement comprising employing as the first developing bath an aqueous developing solution comprising:

Water to make 1.0 liter.

4 2. A photographic developer solution according to claim 1 which comprises:

Ethylenediamine tetra-acetic acid "grams" 0.8 Sodium sulfite do 20.0 Metol do 3.0 Hydroquinone d0 6.0 Sodium bromide do 2.0 Sodium carbonate do 45.0 Potassium iodide "milligrams" 10.0 Sodium chloride "grams..- 100.0

Water to make 1.0 liter.

References Cited UNITED STATES PATENTS 2,979,406 4/1961 Taylor et al. 96-66 NORMAN G. TORCHIN, Primary Examiner E. C. KIMLIN, Assistant Examiner US. Cl. X.R. 96-50, 55, 66