US1954452A - Method of making color photographs - Google Patents

Description

Patented Apr. 10, 1934 UN TED. STATES METHOD OF MAKING COLOR PHOTOGRAPHS Leopold D. Mannes and Leopold Godowsky, Jr.,

. New York, N. Y.

No Drawing. Application March 19, 1930, Serial No. 437,267

4 Claims.

This invention relates to improvements in color photography and particularly to improvements on the processes disclosed in our prior Patents Nos. 1,516,824, granted November 25, 1924, and

5 1,659,148, granted February 14, 1928, and pending application Ser. No. 531,356, filed Jan. 24, 1922.

In theabove mentioned disclosures, colors on the finished negative and positive were obtained by coloring the silver image by processes of metallic toning (conversion to insoluble and colored metallic salts) or dye-toning (converting the silver image to a metallic salt acting as mordant fori an'iline dyes). These methods, while practicable, have certain disadvantages which are in a large measure overcome by the present process.

The main object of the present invention is to substitute, in a process of the type described, a method ofv color development for such colortoning or dye-toning, this method of color-development being applicable for all of the socalled primary colors used, in color photography. It is well known that certain organic photographic developers; i. e. reducing agents, such as dimethylparaphenylenediamine-hydrochloride used in connection with materials hereinafter to be called color-formers for instance, alpha- ,naphthol, have the property of precipitating or forming in situ-with and. in the presence of the I silver reduced from the silver halide a substantially insoluble colored compound such as an indoaniline or an indophenol, which, after the silver image has been removed in solution (potas-. sium cyanide, for instance) remains colloidally dispersed in the gelatine layer giving a substantially transparent colored image in propertion to the extent and depth of the original silver image. This method of obtaining colored images applied to the processes above mentioned disclosed by us not only facilitates clean working because of avoiding mutually deleterious and diverse chemical procedures, but gives purer and more transparent colored images under practical working conditions. It also facilitates the color-development to the point of allowing three successive coatings of differently color-sensitive emulsions on one support, to give a three-color process.

There are two principal ways of applying this" method to the above process, and it is understood that the number oflayers of diflferently sensitized emulsion to be treated is not limited to two or three, though three layers is generally the maximum number desired. The first way is to incorporate in the gelatine of each separate emulsion, before coating, a minimum but sufilcient quantity of the color-former suitable for coloring by development the imagerecord of that emulsion the color desired. These color-formers are sparingly soluble and therefore have a negligible tendency to wander from one layer to another. Treatment after exposure with a single development will cause the image-record in each layer to be colored according to the colorformer which it contains.

The following describes, for the sake of simplicity, a two-color process: Next to the support is coated a red-sensitive emulsion. Over it is coated a green, or blue-green sensitive emulsion containing yellow dye to prevent the blue light from affecting the lower emulsion. In the gelatine of the red-sensitive layer is dispersed or dissolved a small quantity of phenol, of tri-chlornaphthol, or of suitable color-goxrmers. Inthe gelatine of the blue-green sensiti e layer is dissolved or dispersed, a mixture of paranitrobenzylcyanide and ethyl acetoac'etate or other suitable color-formers. After exposure the plate, film, or paper, is developed in diethylparaphenylene-diamine or related compound forming a blue-green image in the lower layer and an orange-red image in the upper. Obviously the choice of colors may be reversed or changed altogether if desired. "A positive plate, film, or paper is coated in the same manner and a print made from the colored negative by direct exposure through contact or projection. The reversal brings the colors of the picture back to normal. The same procedure is applied to three colors, using three coatings. After development the metallic silver, and silver halide left undeveloped may be removed with potassium ferricyanideand sodium thiosulfate. 1

A second method, involving no substantial change in the manufacture of the sensitive material described in the previous patents and application referred to, is to separate the treatment of the developed, fixed and washed film or plate for subsequent coloring by methods of controlled diffusion of chemical solutions employed as disclosed in our prior patents. The coatings may be simultaneously bleached in potassium ferricyanide and the upper one (or two in the case .of triple-coating) alone redeveloped by controlled diffusion of a concentrated developer. The undeveloped lower layer, still containing an image-record in silver ferrocyanide, may be developed by immersionin a color-forming developer as described above which will not affect the redeveloped silver of the upper layer or layers. The plate, or film, may be fixed in sodium thiosulfate, washed, and then dried, and the remaining layer or layers bleached tosilver ferrocyanide, for redevelopment in another color-forming developer, and so on to the third coating in 5 the case ofthree-color photography. After the three steps of coloring, the remaining metallic silver formed in the color developers is removed by solution in sodium thiosulfate and potassium ferrocyanide, or some other solvent of silver. The colored negative is printed on a similarly coated positive which in turn is color-developed substantially as described for the negative.

Instead of this method of separation by controlled diffusion of concentrated redeveloper, the negative may be treated as follows:

The plate or film is developed, fixed and dried. The top layer is converted to silver ferrocyanide by controlled diffusion of potassium ferricyanide in solution. Treatment with a color developer will then affect this bleached layer only. The silver may be removed from this top image-record by controlled diffusion of any suitable silver-solvent. The. lower layers .are successively treated in this manner using a different color developer for each, until only pure color records remain.

Obviously-this method depends on controlled diifusion of the potassium ferricyanide employed.

"In the case of triple-coating for three-color photography it-is often desirable for reasons of balance, to coat the red-sensitive layer between the green-sensitive layer which is next to the support and the blue-sensitive layer on top containing the yellow dye. It is also practicable to coat twice only, having the lower layer red-sensitive and the upper green-sensitized, and then before exposure removing the color sensitizer near the surface, using, for instance, an alcoholic or partially alcoholic solution of yellow dye and dis place the green sensitizer. This gives a sensitive element substantially blue-sensitive at the surface, green-sensitive below, and red-sensitive near the support. As the layer of the blue record is somewhat thin and allows of separate treatment by controlled diffusion, a master positive may be made by reflected light exposure, 1. e., rephotographing, to beused later, for example, in preparing an imbibition matrix for applying the yellow color to the finished print. After refiece tion printing the surface record may be dissolved and removed after drying and the remaining lower layers treated for the two colors only. This method of treatment of the exposed plate may also be applied to triple coatings.

The term "color-former here used refers to organic compounds acting as couplers-in connection with certain developers in photographed processes, thus forming colored compounds, usually insoluble in water, in the presence of the finely divided silver being reduced by the developing agent. This, in general, distinguishes them from leuco-bases and rather classifies them as intermediate couplers in a dye-forming process.

Phenols, naphthols, cresols, nitrophenylacetonitriles, ethyl acetoacetate, and their halogenated or sulphonic acid compounds are typical members of this type of color-former.

Paraphenylenediamines and paramidophenols are typical developers used in conjunction with the color-formers.

The color compounds so formed belong to the class, for instance, of indophenols, indoanilines, and indamines.

We claim:

1. The process of forming two-color component images in registry on a 00111111011 photographic-element that comprises forming two latent images, transforming said images by development into silver images by a process which includes the formation also of a color image corresponding to one of said original latent images, transforming the other developed image into a developable image, and then developing this into a silver-and-color image, the color being different from'that of the first-named color image, and removing the silver from both images, leaving two differently-colored images. 2. The process of forming two-color component images in registry in two superposed sensitized layers that comprises forming a colorcomponent latent image in each layer, transforming each of said images into a silver image by a process which involves also the formation by development of a colored image in the lower layer, transforming the developed image in the upper layer into a developable image, and developing said image in a color forming develop er yielding a color different from that in the lower layer, whereby differentially colored images are formed in the two layers.

3. The process of forming two-color compo nent images in registry in different strata of a single photographic element that comprises forming a colorcomponent latent image in each of two strata, transforming each latent image into a silver image by a process which includes also the development of a color image in one stratum, and transforming the developed image in the other stratum into a color different from that in the first stratum.

4. The process of forming two-color component images in registry on a common photographic sensitive element that comprises forming two latent images in registration in difl'erent strata of said element, developing in a single bath both images into' black, undyed silver images, fixing the element, transforming the silver images into developable silver salt images and transforming them differentially at difierent times and by different development baths into developed images of silver and of different colors, and then removing the silver only, leaving two images of different colors in the two strata;

LEOPOLD GODOWSKY, JR.

LEOPOLD D. MANNES.