US2476541A - Process for producing multilayer color negatives containing masking images for colorcorrection purposes - Google Patents

Description

Patented July 19, 1949 GOLOR NEGATIVES CONTAINING MASK ING IMAGESEJFOR COLORZ-CORRECTION PURPOSES Joseph S. Friedman, Johnsonj.City, N; YI, assignor toiGeneral Aniline & Film' Corporation;- New York, NzYi, a corporation ofDelaware No.-Drawing-.-; Application ;November' 18,1947,

Serial No. 786,809

- 4 Claims.

This invention relates to color photography, andrmoreparticularly :to .a process of producing multi layer color. negativescontaining masking images imthe cyanrand magenta layers for color correction purposes::-

In ;the productionof 1- color: prints from' multi layer; color; negatives; the-color negative consists ofeyellow, magenta, and cyan images in the dif ferentglayers: The-cyan image represents thered, the: magenta imagezthe green, and the ye1'-- low image the: blue arecord: of the original subject; Colorrpositi've printsw or transparencies may-be obtained from sucl-icolor negatives by directuprinting: ontoa multi-la'yer color positive film or.paper;or-by-makingeolor separation negatives whichrare used for making the color positive prints. Thesezcolornegatives-do not, as a" rule, completely satisfy the spectral requirements for trichromatic -co1or H reproduction. For instance;- the. magenta; colored image, formed by the imposition of greeniightuponthe green sensi-' tive; layer; records-thegreen .densities- This im age. should' transmit: the. blue and the redpri- 1 maries completely. To: the-extent to which it absorbs blue-"light, it-superimposes a pattern of the-green densitiesuponzthe blu'ey-with consequent color falsification. This color-falsification makes itself: mam'festawhen the color negative is t0,-be printed; That part ofthe exposure which" is due to bluezllght; andiwwhich should formarecord only. of ,the image; in the. -yellow layer of the negative, forms a record of the yellow image admixed witnthe' record" of :the magenta. The image in :they .blueisensitive part -of the copy ma terial, is, therefore, very impure, and serious color degradationres-ultsz.

It is possible to overcomethis defect if procedures are devised to register a pattern of the magenta dye image, equalinvintensity to the degree to' which .themagenta dye-absorbs blue light, but oppositeiin: character, with: the yellow: dye. im-- ages In a similanma-nner, the. cyan dyeimage can be= corrected; .for; its: blue-absorption: Thesemasks or modifying images can 1 be yellowin color, assuggested by the prior art, ortheyycanr be-a neutral gray, composedof fdye or.silver.-

Numerous methods have been proposed for makingcorrections in these dye images. Gen-:1 erally, "these" methods are characterizedv by. the;- factthat'the'mask is on a separate piece. of. film and must be registered with the original.by.man-.-.- ualor'm'echanical means. This creates problems r of registry ari'singfrom the dimensional variations ,of filmraseitiages'zandrprobleins of definition arising-jimmylackaofiopticalsoontact between orig inaleandnmask, Newtomrings; :etc: It is desir 2 able, thereforetohave the mask integral with the original; To accomplish] this, it has been proposed'to place an" auxili'aryemulsion layer" within .the pack in which the mask could" be formed... While" this gives a desirable result, it; introduces complications into the structure and, the preparation of the monopack material. Since the maskingimage isopbosite in'character to the onethatit'is desiredf'tomodify, emulsions. with special properties have to be used;

To" eliminate "this complication, it was proposed; in'B'ritishlPatent 5 41',266,'t'outi1ize the re sidual silver-halides. in-the. emulsion after the latent image had been-processedto a dye image, and to convert the residual halides, after a proper exposure, into a .bla'ckiand white silver mask... Theprocedure disclosedjto accomplish'the formationof a mask, involved the treatment of the... after. negative color. development in a bleach; bath to'convert'the silverto silver chloride, re-. moyal of the silver chloride by treatment with ammonia or, ammonium sulfit'e; exposure of the. untouched residual silver bromide to white light,,. and'development' in an,.M., Q; developer that... yields a silver, image. Whenprocessed in thismanner; there are formed silver. images in each; ofthe layers of .the color film. This may be de-, sirable'. under certain conditions, butfor certain purposes the presence of a mask representing an image .of the yellow dye pattern is harmfuland, undesirable. This' was recognized by the British. patentee and hespecifically, states in his specifiecations that'the bleach, to be used to effect a con--, version of'the silver. to' silver. chloride, be ofsuch. a mildnature that-.itidoes notdestroythecolor sensitivities. ofthe reen. andred sensitive layers; After treatment withjsuch a mild bleach solution itbecomes possible to'selectively expose the red; and/or green sensitive layers, so that masking. images are formedjionly in these. parts,

The restriction that a .bleachbe used that is. so mild .that' it does. not. destroy the color sensitivity of.'the green andredlayers, severely limits the operator using themat'erial andthe manufacturerwho makes it. The patentee cites a.

number of sensitizing agents that could :be used which willnot be destroyedby the extremelymilcr.

agents he mentions... But,:genera1ly, subjecting;

that, materiallalmost. .to the vanish-ing=point.- To

effect a selective exposure in the green and red}; sensitive layers-.would-require such long durations as a makeqtheiprocedure impractical unless special sensitizers be used which are. not so affected.

Another method, recently proposed, consists of forming masking images in the original green and red sensitive layers by a reversal processing. The procedure proposed, to accomplish the formation of a mask, is to color develop the exposed multi-layer color film and then subject it to the action of a special fixing bath whose penetration into the depth of the emulsion layer can be controlled and the fixing action thereof limited to the upper-most blue sensitive layer. By this procedure, the residual silver-halides in the blue sensitive layer are removed and can no longer be used to form a masking image, whereas the residual silver-halides in the green and red sensitive layers are substantially unafiected and masking images are formed in these layers upon subsequent exposure and development.

The use of a controlled fixing bath, whose action is limited only to a green layer, presents a complex problem. For instance, it is extremely diificult to prepare such a bath which will have no efiect whatsoever upon the residual silverhalides in the other two layers, due to the complication of maintaining a sharp line of penetration as the bath solution becomes absorbed or diffuses through the gelatin.

It is, therefore, an object of the present invention to provide a method for obtaining, in subtractively colored multi-layer photographic color negative materials, masking images composed of silver which correct for the color deficiencies of the cyan and magenta dye images thereof.

A further object is to provide a method for obtaining color corrected color negative materials wherein the color correction is integrally bound with the cyan and magenta dye images.

Other objects and advantages of this invention will be apparent by reference to the following specification, in which its preferred details and embodiments are described.

The foregoing objects are accomplished by developing an exposed, color-developed, bleached, and re-exposed color negative film in the usual black and white developer containing a small quantity of a reagent which will govern the depth at which development will start. These reagents, such as l-mercapto-benzimidazol, l-mercapto-benzimidazol-4-sulfonic acid, phenyl-mercaptotetrazol and Z-mercapto-benzthiazol, do

not function as developers, or fog-inhibiting agents. Their function is to control the extent below the top surface of the emulsion layer at which development is initiated. During this controlled depth development, the reagents desensitize the upper strata of the emulsion grain layers. The developing solution probably diffuses much faster than the control reagent. Hence,' in the deeper sections of the emulsion layers, i. e., the magenta and cyan layers, the developing solution acts normally as though the reagent were absent, since by the time the development action starts, said reagent will have not penetrated to the deeper sections of the emulsion layers. In short, all developing action is stopped in the yellow or uppermost layer, but not in the cyan and magenta layers. As a result of such development, silver images will be produced in the latter two layers but not in the uppermost, yellow, layer. By this controlled depth development, there is achieved the formation of colorcorrecting silver images in the magenta and cyan layers.

In practicing the present invention, the process involved comprises the following steps:

1. Exposure of the color negative film.

'Diethyl amino aniline grams 2. Development of the latent images with a color developer.

3. Short-stopping with an acid bath and washing in running water.

. Bleaching, i. e., converting, of all the silver negative images and any other silver, such as the colloidal silver that may be present in the yellow filter and anti-halation layer, into silver bromide by any bleach bath which does not impair the dye images already present. 4

5. Exposure of the film to a controlled quantity of white light.

6. Development of the masking images by means of a black and white developer, containing from 0.02 to 0.4 gram of the depth controlling reagent per liter of developer for a period of time ranging from 2 to 10 minutes.

'7. Fixation of the unused silver bromide.

8. Washing and drying in the usual manner.

It is to be noted that, during. the bleaching of the exposed and color-developed film, the bleach bath reconverts the negative silver images to silver bromide, and these newly formed silver bromide grains are light-sensitive, so that upon re-exposure and development with a developing agent containing these depth controlling reagents, the latent images of silver bromide grains form silver images. The sensitivity of the reformed silver bromidegrains is very much less than the sensitivity of the residual silver bromide left after color-development. Hence. ample sensitivity differential exists between the silver bromide formed by the rehalogenation of the negative silver image and the residual silver bromide to allow the formation of latent images only in the residual silver bromide.

It should be pointed out that some of the reagents, hereinbefore described, which control the depth at which development begins, have been utilized in the past as anti-fogging agents in developing baths. All of such reagents which have been used for the latter purpose, however, are not operable in the process of the present invention. Although any black and white developer to which such a reagent has been added may be employed, I prefer those developers which contain hydroquinone, or p-aminophenol as the reducing agent, because they have the least effect upon the dye images formed in the three layers.

The foregoing description of my invention will be more apparent from the following examples which are set forth merely to illustrate and should not be construed as a limitation thereof.

Example I A multi-layer photographic color film, such as prepared according to U. S. Patents 2,179,228; 2,179,239; 2,186,849; 2,220,187 and 2,357,388, was exposed to a colored object and then developed for 15 minutes in a color developer of the following composition: a

2-amino-5-diethylaminotoluene mono HCl grams 1.0 Sodium sulfite do 0.5 Sodium carbonate do 67.5 Potassium. bromide do 2.5 I-Iydroxylamine HCl .-do 0.5 Water to make liter 1 This development resulted in the formation of negative silver and color images 'at the exposed portions of the multi-layer film. The color-des m an iota'ssi'ummromide do 15.0 Disodium phosphate d 40.0 Sodium sulfate r do 22.5 Water to make liter 1 depth developer of the following composition:

p-Aminophenol grams 5.0 Sodium sulfite do 40.0 Sodium metaborate d0 40.0 Potassium bromide do 8.0 l-mercapto-benzimidazol-4-sulfonic acid do 0.4 Water to make liter 1 The developed film was then Washed, fixed, and dried in the usual manner.

During the masking development, the exposed silver-halides present in the cyan and magenta layers were reduced to metallic silver thereby forming in each such layer a masking image composed of metallic silver to provide for color correction in printing. No development took place in the yellow (uppermost) layer.

Example II Example I was repeated with the exception that after the bleaching treatment and re-exposure, the film was further developed in a depth developer of the following composition:

Hydroquinone grams 5.0 Sodium sulfite do 30.0 Sodium carbonate do 50.0 Potassium bromide do 5.0 2-mercapto-benzthiazo1 do 0.1 Water to make liter 1 This development was carried out for 3 minutes so that all exposed silver-halide grains Were developed to metallic silver so as to provide masking images in the cyan and magenta layers for color correction and printing.

The developed film was washed, fixed and dried in the usual manner.

Example III Example I was repeated up to and including a bleaching treatment and re-exposure of the bleached film. The re-exposed film was then developed in a depth developer of the following composition:

Hydroquinone grams 50.0 Sodium sulfite do 30.0 Sodium carbonate do 25.0 Potassium bromide do 2.0 Phenyl-mercaptotetrazol do 0.2

Water to make liter 1 l -lie devlbped film was then washed, fixed-arid un a 'm-theusual mariner. v The' proced-ure "of 'tlie rom-going examples 'the advantage 1 over other masking methods in that it ciits 'down th'e" umb'er'of processing steps and rdiices' "the ti-ri-ie i'dl. processing. 7 Obviously, the practice of the present' inve'nti'on -is 'not to b'limitedto theprocessing'of 'multilayer photographic colorfilm of thetype set forth in -the examples. li/Idlti-layer photographic film "such a prepared according to United :Stats 'P-atiits- 22692158 66, 44 3; 2,272 ,191 2,284,877; 2,289f803; 253'04940; 2,3l1 ,020; 2,350,380; 2,397;- '864'-*5 6---and 7, -and the' like can also be processed into color negatives-"containing masking images in a'c'cordance with 'tl'ie present invention. Various other modifications will occurto those-skilled iri the art whichfihowever, donot depart fromthe spirieerrd n ature df 'this 1 invention and I do not intend to be limited in the patent granted except as required in the following claims.

I claim:

1. In the production of subtractively colored negatives with correction printing masks, integrally bound therein, for multi-layer film comprising an impermeable support bearing superimposed silver-halide emulsion layers containing color-formers and being respectively sensitized to the blue, green, and red regions of the spectrum, the blue sensitive layer being outermost, by exposing said multi-layer film to a 'colored object, color developing whereby yellow, magenta, and cyan images are formed in the respective layers, bleaching, and re-exposing the same, the improvement which comprises developing the re-exposed silver-halide layers to positive silver images only in the magenta and cyan layers in a black and white developer containing from 0.02 to 0.4 gram per liter of developer of a depth controlling reagent selected from the class consisting of l-mercapto-benzimidazol, 1- mercapto-benzimidazol-i-sulfonic acid, phenylmercaptotetrazol and 2-mercapto-benzthiazol.

2. In the production of subtractively colored negatives with correction printing masks, integrally bound therein, for multi-layer film comprising an impermeable support bearing superimposed silver-halide emulsion layers containing color-formers and being respectively sensitized to the blue, green, and red regions of the spectrum, the blue sensitive layer being outermost, by exposing said multi-layer film to a colored object, color developing whereby yellow, magenta, and cyan images are formed in the respective layers, bleaching, and re-exposing the same, the improvement which comprises developing the reexposed silver-halide layers to positive silver images only in the magenta and cyan layers in a black and white developer containing from 0.02

to 0.4 gram per liter of developer of a depth controlling reagent consisting of l-mercapto-benzimidazo1-4-sulfonic acid.

8. In the production of subtractively colored negatives with correction printing masks, integrally bound therein, for multi-layer film comprising an impermeable support bearing superimposed silver-halide emulsion layers containing color-formers and being respectively sensitized to the blue, green, and red regions of the spectrum, the blue sensitive layer being outermost, by exposing said multi-layer film to a colored object, color developing whereby yellow, magenta, and cyan images are formed in the respective layers, bleaching, and i e-exposing the same, the

improvement which comprises developing thereexposed silver-halide layers to positive silver images only in the magenta and cyan layers in a black and white developer containing from 0.02 to 0.4 gram per liter of developer of a, depth controlling reagent consisting of Z-mercapto-benzthiazol.

4. In the production of subtractively colored negatives with correction printing masks, integrally bound therein, for multi-layer film comprising an impermeable support bearing superimposed silver-halide emulsion layers containing color-formers and being respectively sensitized to the blue, green, and red regions of the spectrum, the blue sensitive layer being outermost, by exposing said multi-layer film to a, colored object, color developing whereby yellow, magenta, and cyan images are formed in the respective layers, bleaching, and re-exposing the same, the

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,159,600 Murray et al May 23, 1939 2,192,891 Borst Mar. 12, 1940 2,203,653 Evans June 4, 1940 2,431,996

Duerr et a1 Dec. 2, 1947