US2931725A - Coloring of photographic images - Google Patents

Description

United States Patent f p 2,931,725 COLORING F PHOTOGRAPHIC IMAGES Roger M. Ferryman, South Euclid, Ohio, assignor to Metalphoto Corporation, Cleveland, Ohio, a corporaton of New Jersey No Drawing. pplication March 25, 1957 Serial No. 647,972

3 Claims. (CI. 96-58) This invention relates to precedures for the coloring of photographic images and to novel products obtained thereby. More particularly, it relates to methods for color-toning photographic images obtained by the development of photosensitive salts carried in the pores of anodizled layers on aluminum or aluminum alloy base materia s.

Photographic materials comprised of an aluminum base impregnated with photosensitive salts are already described in United States Patents 2,115,339, issued April 26, 1 938,, 2,126,017, issued August 9, 1938, and 2,766,119, issued October 6, 1956. These patents describe a process in which an anodized aluminum base is impregnated with an aqueous solution of silver salts which are then converted to silver halides and thereafter exposed and suitably developed and fixed to yield sharp images of excellent contrasts with a high degree of resolution; Unfortunately, the images produced are restricted in color. The'image obtained isdue chiefly to the color of precipitated silver and tends to be brown-black in actual practice. 'As'disclosed in the patents this precipitated silver image may be toned by treatment with a conventional gold toner, such as Ansco No. 231 toner, an aqueous solution comprising gold chloride and ammonium .thiocyanate (NH CNS). The resulting image is an attractive blue-black color not too different from the usual brown-blacks. Those skilled in the art will appreciatc there are many practical advantages to be realized if images of any desired color could be produced at will.

I have now discovered that, by a relatively simple technique, it is possible to obtain a wide range of brilliant colors and tones which possess the desired stability when exposed to corrosive conditions and under Widely variable atmospheric conditions. In accordance with my invention and depending on the extent to which the sensitized substrate is exposed to heat and depending also on whether or not additional chemical treatment is employed, permanent and stable reds, yellows, blues, greens, lavenders, browns, and the like, are obtained. Indeed, by following the teachings of my invention it is possible to obtain the whole spectral range of color in the form of exceptionally stable products, unaffected by extended exposure to light, including ultraviolet light, highly humid atmospheres and widely varying temperatures from 32 F. up to at least 750 F.

In all of the following examples which illustrate the process, a porous coating was first formed on an aluminum or aluminum alloy surface by electrolytic oxidation, preferably DC, in which the bath consisted of a mixture of alkali oxalates and oxalic acid at a pH between 1.0 and 5. The anodization was carried out at temperatures between 40 and 70 C. at current densities of from 0.5 to 5 amperes per square decimeter. Under these conditions, after anodization for A to 1 hour, highly porous oxide coatings having a thickness between 0.0005 and 0.0015 in. were formed. If A.C. was used, a film thickness of 0.002 to 0.0005 in. was obtained. Both techniques are useful. After the anodization, the plate was thoroughly washed in running water, then in a dilute solution of sodium hydroxide, 1 to 2 percent, and finally in running water, and then was dried at a temperature 80 C. or below. Other known anodizing procedures may of course, be employed.

After a suitable porous layer is formed on the surface of the aluminum substrate it is impregnated with a photosensitive silver halide in any known manner, for instance by any of the procedures described in the aforementioned patents. The formation of the sensitized plate and its subsequent exposure and development are all accomplished in accordance with known procedures and form no part of the present invention.

In a first embodiment a batch of aluminum photographic plates were anodized, sensitized, exposed, developed and fixed. These plates were heated to temperatures greater than 600 F. in a darkened furnace. This caused the silver image to bleach out completely and to disappear from the surface of the plates. It was then found that the image could be made to reappear with a different color. by exposing the bleached-out imagecontaining plate to ultraviolet light, or to specific chemicals or combinations of chemicals. The following examples are illustrative of these aspects of my invention.

An aluminum plate bearing a silver image, produced in the manner previously described, was heated at 700 F. for 15 minutes and the image was found to have been entirely bleached out. The plate was then exposed to a 500 watt ultraviolet lamp at a distance of one foot from the plate. Within 30 seconds a gold bronze image of relatively high contrast appeared. Continued exposure to ultraviolet light did not change the color or contrast. Another similarly prepared aluminum plate bearing a silver image, was heated for 15 minutes at 900 F. and, again, the image disappeared. On exposure to ultraviolet light as described above, a pale yellow-bronze color image developed. Still another sample was heated to 1150v F. for 15 minutes and again the image disappeared. On exposure to ultraviolet light, a pale yellow image of easily legible nature developed. In each case, these images were found to be stable when subjected to weather omcter and corrosion tests.

Instead of treating plates bearing the bleached-out image with ultraviolet light, it has been found that the heat-treated silver image is much more amenable to toning after the bleaching heat treatment than had been the case prior to any heat treatment. The following examples illustrate this procedure.

Samples of silver image plates were heat treated for 15 minutes each at 700, 900, and 1100 F. respectively and, in each case, the silver image was bleached out. These were then immersed in a 5 percent solution of ammonium sulfide at the boiling point, removed from the solution, washed in running water, and then dried. The sample which had been heat treated at 700 F. developed a rich brown color. The sample heated at 900 F. developed a golden yellow color, and the sample heated at 1100 F. developed a pale bronzy yellow color. A similar range of yellows, golds, and browns were obtained by treatment of plates bearing the heat-bleached images with solutions of sodium sulfide, potassium sulfide, and barium sulfide at pHs between 5 and 7. Virtually any soluble sulfide can be substituted for the alkali and alkaline earth sulfides specifically illustrated, provided the pH of the toning solution is suitably adjusted to the range of 5-7. Other chemical agents may be employed in place of the sulfides, or to supplement the toning achieved with the sulfides.

A silver image-bearing sample was bleached by heating in air to 900 F. for 15 minutes and was subsequently Patented Apr. -5, 1960 treated with a percent pH for 5 minutes at the boiling point. After thorough washing, the image was further treated with a 1 percent solution of gold chloride at room temperature for 5 minutes and an image with a bright red color was thereby obtained.

Other plates bearing silver images were bleached by heating for 15 minutes at 900 F. On cooling, the plates were immersed first in a 5 percent water solution of potassium ferricyanide for 15 minutes, washed, and then placed in an aqueous solution of vanadyl sulfate and retained in the solution for minutes. ,After washing and drying, an image having a permanent deep yellow color was obtained. A plate similarly bleached was immersed in a solution containing 5 parts of potassium ferricyanide by weight in 100 parts of water, washed, and then placed in a solution of 5 parts of ferric oxalate in 100 parts of water, and the immersion continued for 10 minutes. After washing and drying, the image was found to be blue. Another group of plates were bleached by heating and then treated as described above with potassium ferricyanide and vanadyl sulfate solutions. After the yellow image had developed completely, the plate was removed from the vanadyl sulfate solution, washed thoroughly, and then immersed in a 5 percent solution of ferric oxalate for a period of 5 minutes. The image turned into a brilliant green. Although toning processes are reasonably common in the field of photography, it is significant to note that the color changes which were obtained were not possible on this type of photosensitive system prior to the heat treatment, but only after the image had been bleached by the heat treatment referred to. Furthermore, these colored images are permanent and stable.

The examples set forth above are to be taken as exemplary only and as indicative of the fact that by judiciously introducing a heat treatment into the image coloring process, permanent images extending over the full range of spectral colors are ultimately obtained, which are stable in a wide variety of environments.

In the final step of the process above described, the colored image is sealed in the anodized layer in the same manner as described in the US. patents to which reference has already been made.

solution of sodium sulfide at Having now described my invention in the manner prescribed by statute, I claim:

1. In a process in which a silver image is formed in the pores of an anodized surface of a sensitized aluminum plate by impregnating a suitably prepared aluminum substrate with a silver halide salt, exposing the sensitized plate and developing and fixing the exposed plate to produce an imageof silver thereon, the improvement which comprises: heating the plate bearing the said developed and fixed image to a temperature between about 700 F. and 1150 F. in a darkened furnace for a time sufiicient to bleach out the image and thereafter exposing the plate bearing the bleached image to ultraviolet light to cause the image to reappear with a yellowish color.

2. In a process in which a silver image is formed in the pores of an anodized surface of a sensitized aluminum plate by impregnating a suitably prepared aluminum substrate with a silver halide salt, exposing the sensitized plate and developing and fixing the exposed plate to produce an image of silver thereon, the improvement which comprises: heating the plate bearing the said developed and fixed image to a temperature between about 700 F. and 1150 F. in a darkened furnace for a time sufficient to bleach out the image and thereafter causing the image to reappear in a desired color by treating the plate bearing the bleached out image with an aqueous solution of a salt which will tone the bleached-out image.

3. The heat-stable product of the process according to claim 1.

References Cited in the file of this patent UNITED STATES PATENTS 616,706 Hausermann Dec. 27, 1898 809,651 Vathis Jan. 9, 1906 2,732,298 Stookey Jan. 24, 1956 2,766,119 Freedman et al Oct. 9, 1956 I FOREIGN PATENTS 2,580 Great Britain Sept. 13, 1906 407,830 Great Britain Mar. 29, 1934

Claims (2)

1. IN A PROCESS IN WHICH A SILVER IMAGE IS FORMED IN THE PORES OF AN ANODIZED SURFACE OF A SENSITIZED ALUMINUM PLATE BY IMPREGNATING A SUITABLY PREPARED ALUMINUM SUBSTRATE WITH A SILVER HALIDE SALT, EXPOSING THE SENSITIZED PLATE AND DEVELOPING AND FIXING THE EXPOSED PLATE TO PRODUCE AN IMAGE OF SILVER THEREON, THE IMPROVEMENT WHICH COMPRISES: HEATING THE PLATE BEARING THE SAID DEVELOPED AND FIXED IMAGE TO A TEMPERATURE BETWEEN ABOUT 700*F. AND 1150*F. IN A DARKENED FURNACE FOR A TIME SUFFICIENT TO BLEACH OUT THE IMAGE AND THEREAFTER EXPOSING THE PLATE BEARING THE BLEACHED IMAGE TO ULTRAVIOLET LIGHT TO CAUSE THE IMAGE TO REAPPEAR WITH A YELLOWISH COLOR.

2. IN A PROCESS IN WHICH A SILVER IMAGE IS FORMED IN THE PORES OF AN ANODIZED SURFACE OF A SENSITIZED ALUMINUM PLATE BY IMPREGNATING A SUITABLY PREPARED ALUMINUM SUBSTRATE WITH A SILVER HALIDE SALT, EXPOSING THE SENSITIZED PLATE AND DEVELOPING AND FIXING THE EXPOSED PLATE TO PRODUCE AN IMAGE OF SILVER THEREON, THE IMPROVEMENT WHICH COMPRISES: HEATING THE PLATE BEARING THE SAID DEVELOPED AND FIXED IMAGE TO A TEMPERATURE BETWEEN ABOUT 700*F. AND 1150*F. IN A DARKENED FURNACE FOR A TIME SUFFICIENT TO BLEACH OUT THE IMAGE AND THEREAFTER CAUSING THE IMAGE TO REAPPEAR IN A DESIRED COLOR BY TREATING THE PLATE BEARING THE BLEACHED OUT IMAGE WITH AN AQUEOUS SOLUTION OF A SALT WHICH WILL TONE THE BLEACHED-OUT IMAGE.