US2456954A

US2456954A - Photographic reversal processes

Info

Publication number: US2456954A
Application number: US765633A
Authority: US
Inventors: Knott Edward Bowes; Stevens Guy William Willis
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1947-08-01
Filing date: 1947-08-01
Publication date: 1948-12-21
Anticipated expiration: 1965-12-21

Description

Dec. 21, 1948.

Filed Aug. 1, 1947 BLuE A GREEN RED f'mv JENSITIVE B. KNOTT El AL 2,456,954

PHOTOGRAPHIC REVERSAL PROCESSES 2 She'ets-Sheet 1 COLOURED OBJECT LAYER: or EMuwIoN WHICH Fox/w LA TENTIMAGE MOSIZY INSIDE sILvER HAL/DE GRAINS (BLUE sEIvsITIvITr 0F GREEN sENsITIvE AND RED .sENsITIvE L YExs BEING LEss THANZ, THAT or ELuE SENSITIVE LAYER) bLuEsEIvslrlvz RED-SENSITIVE SUPPORT T0 LIGHTED coLouREo, OBJECT AEov TREAT WITH BuEI-AcE'f 'oLoL/R- aRMINa'pEvELoPEIe CONMINING A COLOUR";DUPLEI? GIVING 1A BwE- GREEN IMAGE LAYERs of EMuLsmN CONTAINING NEaATIvE LATENT -"IMAG'E MOSTLY INSIDE THE .sILvL-R HAL IDE GRAINS AND CfAP/IBLE 0F FoRMINa'JLIRFA E LA7ENT IMAGE T0 UNIFORM RED LIGHT ZAYERS 0f EMULSION CONMINING NEGATIVE ZATENT IMAGE MOSTLYINSIDF 7H1. SILVER HAL/DE GRAINS SUPPORT A COL DEVELOP IN Jl/RFACI. COLOUR-IGRMING' DEVELOPER CONM/NING Y OUR Ca/PL'EI? GIVING A BLUE" GREEN IMAGE BZUEG'REE-N Cowl/RED PosITIvE EDWARD B OVVES KNOTT GUYWILLIAM WILLIS S'IEVEHIS INVENTORS JUPI'DRT AI'TER WAS /Na, TREAT WITH .sI RI'AcE COLOUR-FORMING DEVELOPER CUNMINING GIVING A MAGENTA lMGZ 286. I J. LL ATTOR EYS A COLOUR couPLEk Dec.- 21, 1948.

E. B KNOTT El AL PHOTOGRAPHIC REVERSAL PROCESSES Filed Aug, 1, 1947 POSITIVE RECORD OF CdOU/PED OBJECT u REE MAG NA MAGENTA /azuz- ERIEEN I E k \J0PP0RT 2v Sheets-Sheet 2 -LAYER OF EMULSION CONN/NINE NEG'ATIVE LATENT IMAGE MOSTLY INSIDE THE JILVER HAL/DE 67M INS AND O4PABLE OF FORM/N6 JUKFACE LATENT IMAGE SUPPORT EXPOSE TO UNIFORM GREEN LIGHT LA YER OF EMULSION CONN/NINE NEGATIVE LATENT IMAGE MOSTLY INSIDE THE .SILVER HAL/DE GRAINS AND REVERSED LATENT IMAGE MOSTLYON THE SURFACE or THE awn/1v: L-SUPPORT DEVELOP 11v JURFACE 629LOUR- I"OI?MING DEVELOPER cou MINING A coma/v COUPLER GIVING A MAGENTA/M1465 LA YEI? Of EMULSION CONTAINING NEGATIVE L/ITEIVT \MAmvm-cowuksp POSITIVE BLUE GREEN CULOUKED POSITIVE SUPPOK T 717577 WITH SURFACE COLOUR-FORMING DEVELOPER I CONTAIN/N6 A COLOUR COUPLER GIVING YELLOW IMAGE LAYER OI EMULSION CONTAINING NEGATIVE LATENT IMAGE MO-SIZYINJIDE THE SILVER HAL/PE GRAINS AND CAPABLE OF FORMING JULIflCEL/ITEIIT IMAGE EXPOSE 7O UNIFOKM BLUE LIGHT surrmrr LAYER OF EMULSION GOA/MINING NEGATIVE LATENT IMAGE MOSTLY INSIDE THE SILVER HAL/DE GRAINS/1ND REVERSED LATEN T IMAGE MOSIZ YON 511K516? 0f If/t' GMINS UPPORT DEVELOP IN SURFACE COLOUR-FORMING DEVELOPER CONTAIN/N6 A COLOUR COUPLER GIVING A )TLLOW IMAGE mow-(01.0mm I y EDWARD BOWES KNOTT Patented Dec. 21, 1948 UNITED STATES PATENT OFFICE PHOTOGRAPHIC REVERSAL PROCESSES Application August 1, 1947, Serial No. 765,633

8 Claims. (Cl. 95-5) This invention relates to photographic processes especially so-called reversal processes and materials therefor.

As is known the latent photographic image formed by the action of light on a photographic silver halide emulsion is not confined to the surface of the silver halide grains but it appears to be also distributed internally throughout those grains. It is possible to develop only the socalled surface latent image by means of developers which have little or no solvent action for silver halide. One of us has described in the literature given below that after removal of the surface latent image the internal latent image can be developed as simply and conveniently as can an ordinary surface latent image if this is done by employing a developer having a solvent action for silver halide; moreover the image so obtained indicated that the speed of the emulsion as measured by the internal image is often comparable with the speed as measured by the surface developed image. Such a developer is for convenience called an internal developer, and an example of such a developer is given on page 47 of the Pho. J 1942, 82, 42.

There is a type of emulsion, which whil known per se, is according to our recent investigations of such a nature that the latent image is formed mostly inside the silver halide grains and there is relatively little surface latent image formed; such emulsions have not found much commercial use, in fact they have for a long time been considered as practically useless. We have now found, however, that after such emulsions have been exposed to form an internal latent image therein, they can subsequently be treated to render them capable of forming surface latent image upon subsequent exposure, and that the extent of the surface latent image forming capability is greatest where the internal latent image was least and vice versa. An example of such type of emulsion is that known as Burton's emulsion given in Walls Photographic Emulsions, 1929, pp. 52-53. Moreover this type of emulsion may be prepared in other known manners, for instance by taking an ordinary silver bromide or silver iodobroniide emulsion containing between 0.5 and 5% silver iodide (based on the total silver halide), and coating it as a layer and then after drying, treating it with the following bath:

Potassium bichromate grams The time of treatment must be sufficient to inhibit surface latent image formation as can easily be ascertained by exposing (after washing) and then treating with developers of Formulae I and III, given below. Such an emulsion layer can then be used as it is or may be remelted and coated again as desired.

In our copending application Serial No. 765,632, filed August 1, 1947, we have applied the aforesaid discovery to give a reversed image in a sensitive layer of a silver salt emulsion.

In the present invention We apply the aforesaid discovery to give a new method or producing reversed photographic images in adjacent emulsions on a single support, as will hereinafter be described.

Various methods are known for producing positive images in adjacent silver halide emulsion layers which have been exposed so as to produce negative latent images therein; such reversal methods are employed in both black and white and in colour photography.

In the present invention such reversal images are obtained by employing for the emulsions the said type of emulsions in which the latent image is formed mostly or entirely internally in the grains; that is to say an emulsion only few or none of whose exposed grains are developable to silver by a developing solution which cannot act as a developer for latent image inside the grains-such a solution is Formula I (below). Whether an emulsion is of this type for the purpose of this invention can be ascertained by treating it (after exposure) in developers of the kind given in Formulae I, II (a) and II (b) and III below. It is of the type defined if it will develop in those of Formula II (a) or (b) but will not develop or will develop only slightly in Formula III and in Formula I.

The developer formulae above referred to are:

FORMULA I SURFACE DEVELOPER p-Hydroxyphenylglycine grams 10 Sodium carbonam (cryst.) do Water to ccs 1000 Development time 4 minutes at 20 C.

FORMULA II (a) INTERNAL DEVELOPER Hydroquinone grams. 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhy. do. 50 Potassium bromide 1 do 10' 3 Sodium hydroxide grams 25 Sodium thiosulphate cryst. do 20 Water to ccs 1000 Development time 3 minutes at 20 C.

FORMULA II (b) INTERNAL. DEVELOPER Hydroquinone "grams" 12 N-methyl-p-aminophenol sulphate do .3 Sodium sulphite (cryst) do 90 Potassium bromide 'd'o -4 Sodium carbonate (cryst.) do --150 Sodium thiosulphate ..do .120 Water to ccs 1000 Development time 4 minutes at 20 C.

FORMULA III COMMERCIAL DEVELOPER This is the, sameas Formula II (b) but omitting the sodium thiosulphate.

Formula'II (a) is a more energetic developer than-Formula II' (b) so that it usually gives a higher effective speed and a higher contrast than Formula II- (b) but is often not so convenient, since it has a higher tendency to aerial oxidation and to give fog.

While in this specification we have described our invention partly in regard to a theory of internal and'surface latent images, the correctness or otherwise of such theory, is not essential to the successful working of the invention, it being only necessary to choose the emulsions according to the tests hereinafter given.

The present invention employs the following types of emulsions:

TYPE .I

These are the emulsions which will develop (after exposure) in internal developers of the kind given in-at least one ofFormulae II (a) and II (b), but will not developor only slightly develop in'jFormula III or in" Formula I.

(1 Normal range of exposure zAsmeasuredaocording to normal-photographic testing technique, 'when'a test layer of .t-heqemulsion :is coated .on a transparent support (e. g. glass) and the layeris exposed to-a light; intensity scalethe whole of which is exposed for some fixedtime between Aooth and'l second andis developed in theinternaldeveloper II (a) the transmitted density obtained at any .point alon the logmE axis over a rangeof 3.0 starting from the-threshold of thecurve (D=0.1 above fog) shouldbe'at least 5'times, and preferably at least times, the transmitted density-obtained when an identical test layer of the emulsion is ,dBVGL- oped with the surface developer of Formula I 01' III, the measurements ofdensity being made at the corresponding (i. e. the same) points on the logioE axis; as indicated, the best (i. e. preferred) emulsions are-thosegiving the-highest density ratios and the very best (i. e. ,most preferred) emulsions can be selected with greater certainty by'substituting Formula II (b) for II (a).

(2),.Small range of exposures For this purpose the emulsion need not conform to such a rigidrequirement, for instance for making a tonecorrecting mask, but it is sufiicient if in thealoove test the upper limit of 3.1 is substituted by an upper limit of 1.0. 1

Y "Since Formula III contains sodium sulphite and Formula I1s free from sulphite,.;and sulphite :is

The reversal process of the present invention depends upon the fact that the type of emulsion :zdefined above, namely one which upon exposure in the ordinary dry state forms the latent image mostly inside the grains, can be treated so as to render it capableofforming surface latent image ,on exposure. .The'treatment depends to some extent upon:thezparticular emulsion. Examples of such treatment are as follows:

(1) All. or nearly all emulsions of the type defined can be treated by soaking in any ordinary developing solution such as Formula I or III employing an organic developing agent and which has .littleor no solvent action on the silver halide.

(2) vIn the case of some emulsions of the type defined which are colour sensitised, the treatment can .be with plain water alone.

The .effect'of any such treatment or any similar treatment for the same purpose canbeascer- .tained by takingan unexposed layer of the emulsion and merely giving it the treatment and then subjecting it to an image-Wise exposure and .if this image can be developed in a developer or Formula I or III, the treatment can be employed in performing the present invention.

:Hence, according to the present invention there is provided the method of producing reversed photographic images comprising .exposing to a lighted object or image a photographicmaterial comprising on a single support .a plurality of photographic silver salt emulsions of the type herein-defined, then without developing up the latent images so formed in said emulsions, treating at least one of said exposed emulsions to render it capable of formin surface latent image, i. .e. latent "image .developable by the developer of, Formulae I or III, and then while continuing the treatment or after the treatment, uniformly exposing to vlightthe so-treated emulsion to produce'latent image some. of which is developable bythe aforesaid developer I or III, developing the uniformly fogged emulsion in a developer which develops the latent image which is developable bydeveloper I or III and gives no more than :a negligible development of the negative latent image formed by the original exposure compared with the -positive'image which is developed, then uniformly exposing to light another of said eX- posed emulsions which has also been treated (simultaneously with the first-mentionedemuL sion or by a separate treatment) to-render it capable of forming latent image developable by the aforesaid developer I'or III to produce latent image some of which is developable by the aforesaid developer I or III, and developing the second uniformly fogged emulsion in a developer which develops the latent image which is developable bydeveloper I or III and gives no more than a negligible development of the negative latent image formed by the original exposure compared with thepositive image which'is developed in said second emulsion. The unused silver salt may then be dissolved'out in the usual way. Of course, where it is desired to reverse two emulsions consecutively, they must be selectively re-exposed to a uniform exposure.

In one form of the invention there is provided the-method of producing reversed photographic images wherein a material comprising on a single support a plurality of silver salt emulsions of the type hereindefined, is exposed to an object or image, then without developing up the latent images so formed in such emulsions to visible images the exposed material is soaked in a photographic developing solution which is capable of developing a surface latent image but is incapable or only slightly capable of developing the internal latent images formed by the first exposure, and then the material is subjected to a uniform exposure which affects one of the emulsions and is of sufiicient intensity and time to cause a reversed image to develop in the emulsion so exposed on continuing the treatment in the same or another surface developer, and subsequently the material is subjected to a further exposure which affects a further emulsion and is of sufficient intensity and time to cause a reversed image to develop in such further emulsion in continuing the treatment in the same or another surface developer. Such uniform exposures are of course each by light to which the emulsion to be reversed is sensitive and it is preferably of low intensity. The highest contrast in the reversed I of the latent image in a developer such as For- A mula II (a) or II (b) which gives an unreversed image.

In another form of the invention at least-one of the emulsions is a colour sensitised emulsion and the treatment to render it capable of forming surface latent image consists in treatin it with plain water.

The invention includes a sensitive photographic material comprising on a single support at least two sensitive silver salt emulsions both of which are of the type hereindefined, such emulsions being of such character or so arranged in the material that they can be selectively exposed.

When the uniform exposures of the material are made after immersion in a developer such exposures may be adjusted by making tests, so as to give the desired strength of reversed images and to some extent errors in the first image forming exposure can be compensated by so adjusting the uniform second exposure.

To obtain the best results when a reversal exposure is made during treatment of the emulsion after the first exposure, in a developing solution, it is very important that no appreciable development of the reversed image should occur before the completion of the reversal exposure since such development would cause screening of the emulsion grains where it occures and wouldv lead to a reversal effect or to a reduction of the higher densities. To avoid this, one may employ, for instance, a developing solution which is very dilute or whose pH is so low that the surface de-' veloping activity is very small.

Examples of developing solutions having such a low pH are as follows:

A. N-methyl-p-aminophenol sulphate grams 6 It should be noted that for satisfactory results in performing the present invention the emulsion layer, after receiving the first image-forming exposure, must be well soaked with the developing solution before being given the uniform second exposure to produce the reversed image.

An example of a sensitising dye for use in an emulsion with which may be employed, the plain water treatment given above is 5-[2-ethyl- 1 (2) benzoxazolylidene) ethylidene] 3-n heptyl- 1-phenyl-2-thiohydantoin. This is the dye described in Example 3 of United States Patent No. 2,282,116. This dye was used'at the rate of 0.05 gram of dye for each amount of silver halide equivalent to 200 grams of silver nitrate. The dye was added during ripening (i. e. before washing); if the dye is added after washing then a greater quantity should be used."

An advantage of the method of the present invention of producing reversed images is that such type of emulsion can be made to have ahigher effective speed combined with a lower graininess in the image than that of any known to us which is made for giving a reversed image upon direct development (such material is exemplified by that described and claimed in British Patent No. 524,087).

An advantage of the method according to the present invention over known methods in which reversed images are obtained by developing the first formed image to silver and then removing such silver followed by exposure and redevelopment or fogging redevelopment is that only one development is necessary for each image and for black and white work no silver removal bath is required.

In performing the present invention the sensitive material may consist of a plurality of silver salt emulsions of the type hereindefined ona single support which emulsions are of such character or are so arranged that they can be selectively exposed; then it is a simple matter to develop only one of them to give a reversed image in a first developer which is not possible in the known methods where there are employed only emulsions of the type where upon exposure surface latent images are formed on the grains. Further the other emulsion or emulsions can be successively treated in similar manner. The character or arrangement of the emulsions so that they can be selectively exposed can be deter: mined in known manner, for example: I

1. A not specially colour sensitised emulsion having a high blue sensitivity mixed with or superimposed on a green or red sensitised emulsion of relatively low blue sensitivity. 7

2. A green sensitised emulsion mixed with or superimposed on a red sensitised emulsion.

3. Two emulsions between which or in one of which is a material which filters out light to which on of them is sensitive, for instance two not specially colour sensitised emulsions with a blue absorbing filter layer between them or in one of them.

4. Two emulsions coated side by side (i. e. on different areas of the support).

It is obviously of great advantage to be able to develop a reversal image in a first developer since this very materially decreases the number of processing steps and gives a simpler process, especially in colour photography employin three of the kind of emulsion in question. This advan= tage can be seen by considering the case of two superimposed emulsion layers one being for example red sensitive and the other being for ex-v anemone image's if both emulsions are -'f the same typeiareas' follows: "UimINXRY"SU'RFACE'LATENT. "IMAGE-FORMING TYPE Ai red"-sensitised emulsion of this type coated o'ver a' greensensitised emulsion'of the same ty'pe.

After-exposure the. processing normally Deve1op-both layers. ='='2.= =Wash. V

Expose the one-layer uniformly to red light. :Z' LQCoIour develop the re-exposed layer. 5. Wash.

Expose the other layer light.

7. Colour develop this lastre-exposed-layer. --8. ;,-Wash. #9. Remove all silver.

LINTERNAL LATENT IMAGE FORMING TYPE uniformly toggreen SA r'ed sensitised emulsion f this type. coated ever a green sensitised emulsion of the same'type.

' n-fter exposure thepro'cessing can be:

.1 1. While'immersed .in one surface colour-developer exposed uniformly to red light and allow the red record layer to develop.

"2. Wash.

"While immersed inanother surfacecolour 3o developer exposeuniformlyto green lightthrough the ba'ck and allow the-green record layer-to develop.

4. -Wash.

5. Remove all silver.

6. Wash.

Thus, whensuch emulsions are-employed for example as mixed emulsions or superimposed emulsion layers in colour photography, the method of the'prese'n't invention'enables coloured positives to be obtained more expeditiously ona material containing a negative latent image of-a coloured obj ect or colour positive.

"The present invention may be applied to "a three-colour material consisting of three superimposed 'or'mixed emulsions each of the said type sensitised 'to record respectively blue, green and red, in which the red and green'sensitised emulsions have blue sensitivities which are very low, such'a's less than one tenth of the blue sensitivity er the blue-sensitive emulsion (see British Patent No. 540,444) the following procedure may be adopted'to process suonanexposed material. First immersethe material ina surface colour= forming developer containing a colour coupler giving a bluegreen image and thenexpose' the material to a uniform red light; thenegative latent image in the lowest red sensitive layer will then 'develop as a, blue-green coloured positive.

After washing, immerse the 'materialin a "colour-forming surface developer containing a colour-"coupler giving a magenta image andthen expose the material to a green light the negative latent image in the green sensitive emulsionv'vill then develop as a magenta-coloured *positi-ve. Finally, immerse the material in a-"c'olour forming' surface developer containing a colour coupler giving "a. yellow image and then e'xpose the matei'i'al t-o blue light; the negativelatent image in the -=b111e sensitive layer Will then dev'elo'p 'a's a yellow 'coloured positive. Colourforming velopers 'given "such blue-green lmagenta d yellowv images (respectively) suitable for this purposee'arethose of the kin'd coinmonly employed mccelour 'iph'otography which have .1 little or one tendencyi to dissolve 'silver halide such as' 'those-in -gram which depictsigraphically the application of our invention to a three colour m'aterial as desci'ibed above. In the first she'et'of drawings-at 'B is shown a' three-colour sensitive material com prising 5 (308176121 On a support three superimposed silver halid'e emulsion layers which-are red, green and blue sensitive reading from the-support. The blue se'n'sit-ivityii or the red and green sensitive layers is very'low compared to'the' bl'u'e'sensitivity of the blue'sensitive la'y'er,vviz.- less than t; the n's'itive layer. Upon TEX-DQ511132 OT he thl'ecblolir finsltive 'Il'l-Bjte'lil shown at B t e lig ht eolo'uredobjeot shown at A5 negative ateiitimage of the red "'pa'rt' orthe coloured obie s foriiied' mostl inside the silver halide g rains of-the red'sensitivelayer'; a negative latent' iniage of' 'the"gree'n pa'r-t of the coloured object sfoi iiied mostly inside the silverhalide grains fthe'gre'e'n "s'nsitive'layer; :and a'negative latentimage'of the blue 'part of the coloured obje "is iorme'd mostly inside the silver halide grains the elue sensitive layer, as shown at C. Upon tre'atm'ent "of this exposed three-colour materialtorenderit capable of forming surface latent -im age' by immersing it in a surface 'col-o'ur-ierming developer containing a colour coupler g ivi ng a bl-ue green image, the red sensitive layer still 'contain's the aforesaid negative latent image mostly inside the silver halide grains, Uut-is' -now'ca'pableof forming surface latent image as-shevvn'a't D. 'Upon exposing the material to a uniform redlightyareversed '(or positive) latent iinag'e'is'rormed mostly'on the surface of the silver halide grains as shown at E. I Upon development ot theremse'nsitive emulsion layer in the aforesaid sur-iac'e" colour-forming developer containing a--*colo'ur coupler giving a blue-green image,ablife greencoloured positive develops in the r'ed- 'sens'it'iv'e layer as shown at F. After washin'g the "material and upon immersing the washedmaterialdn a surface colour-forming deveiopercontamin a colour coupler giving a magenta'i'mage, the "green sensitive layer still contains -the -'-a"-fo'r'esaid negative latent image mostly i-ri'side tlre"silver halide grains, but is now eapable of formmg surface latent image as shown at G (second sheet of drawings). Upon exposing the material'to un'iform'green light, a reversed or po 's'it'ive'f'la'jtentimage is-formed mostly on the silver halide grains "as shown at H. Upon de velo'pment er the green-sensitivelayer in the aforesaid surface? colour-forming developer containing "a colour coupler giving a magenta image, a' magentacolollred positive develops in the green-sensitive layer as shown at 1. Upon immersing the material in a surface colourformin'g developer containing a colour coupler giving a yel'low image, the blue-sensitive layer still contains the aforesaid negative latent image mostly inside the .silverl'halide grains, but is now capable of "forming surface latent image as shown at J. Upon exposing the material to uniform blue light, a reversed (or positive) latent image is formed mostlyon the surface of the silver halide grains as shown at K. Upon development of the blue-sensitive layer in the aforesaid surface colour-forming developer containing a colour coupler giving a yellowi'inage, a yellow coloured positive "develops in the 'blue-sensitivedayer as shownat L,=and a positive recorder the'colou'red objectis complete. u -An alternativamethodof processing such a three-colour material is illustrated by considering the case where the layers are inthe following order:

Blue sensitive layer Green sensitive layer Red sensitive layer Support.

For example, to process this material after exposure to a coloured object or image, first place it in an ordinary surface, developer (e. g. Formula III) and then uniformly expose to red light-whereupon a reversed image develops (in black silver only) in the red sensitive emulsion; then convert such silver to silver ferrocyanide by treatment with a solution of 2% potassium ferricyanide and then develop with a colourforming developer containing a colour coupler giving a blue-green coloured image. The red sensitive layer is nearest the support then contains a reversed image in red dye plus silver. Next place the material again in an ordinary surface developer (e. Formula III) and then uniformly expose to green light whereupon a reversed image develops (in black silver only) in the green sensitive emulsion; then by means of controlled diffusion convert such silver to silver ferrocyanide without converting the silver in the red sensitive layerj then develop such silver ferrocyanide with a magenta forming colour developer. The top layer isthen treated similarly to the treatment just described for the green sensitive layer except that the uniform exposure must be by blue light and the colour developer should give a yellow image. Finally, all silver and unused silver salt is removed in the usual way. This example illustrates the processing of superimposed layers in sequence so that the reversed image formed in any one layer does not screen the subsequent reexposure of another layer in which a reversed image is to be formed. I

In performing the present invention, it is sometimes found that in the development of one of the reversed images there may be a tendency for some development of the first formed latent images-therein to occur and this gives veiled whites. For instance, this is particularly likely to occur when the emulsion is dye-sensitised; to test for this in any particular case, one should first expose the emulsion layer behind a step wedge and develop in an internal developer (Formula II (a) or II (b) then ascertain therefrom the exposure which gave the maximum density, next over-expose another portion of the emulsion layer (say, four times the amount which gave said maximum density) and now on development in a surface developer (Formula I) the density obtained should desirably be not above 0.05 above the fog density.

This undesirable tendency can be prevented by treating the emulsion (or the whole material) after the first image exposure (but before immersion in the developing solution) in a mild silveroxidising bath such as for 1 minute at C. in

Potassium ferricyanide grams 1 Potassium bromide do 0.5 Water ccs 1000 Such a bath does not seriously affect most sensitising dyes (if present in the emulsion) nor the internal latent image.

Thisapplication is a continuation-in-part of our copending application Serial No. 589,094, filed April 18, 1945.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. The method of producing reversed photographic images comprising exposing to a lighted object or image a photographic material comprising inseparably combined and extending over the same area on a single support a plurality of photographic silver'halide emulsions a test layer of any one of which emulsions coated on a trans- Z parent glass support upon exposure to a light intensity scale for a fixed time between 1/100th and 1 second and development, for 3 minutes at 20 C. in the following developer (IIa):

gives a transmitted density at any point along the logmE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, atleast 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4-.

minutes at 20 C. in the following developer (I) p-I-Iydroxyphenylglycine grams Sodium carbonate, crystals do Water to ccs 1000 the measurements of density being made at the same points on the logmE axis, then without developing up the latent images so formed in said? emulsions to visible images treating an exposed} emulsion to render it capable of forming latent image developable by the following developer (III) Hydroquinone grams N-methyl-p-aminophenol sulphate do Sodium sulphite, crystals do 90. Potassium bromide do 4 4 Sodium carbonate, crystals do Water to ccs 1000 uniformly exposing to light the so-treated emulsion to produce latent image some of which is developable by the aforesaid developer (III), de veloping the uniformly fogged emulsion in a developer which develops the latent image which is developable by developer (III) and gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is de veloped, then uniformly exposing to light another of said exposed emulsions which has also been treated to render it capable of forming latent image developable by the aforesaid developer III to produce latent image some of which is developable by the aforesaid developer (III), and

developing the second uniformly fogged emulsion in a developer which develops the latent image which is developable by developer (III) and gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is developed in said second emulsion.

2. The method of producing reversed photographic images comprising exposing to a lighted object or image a photographic material comprising inseparably combined and extending over the same area on a single support a plurality of photographic silver halide emulsions a test layer of any one of which emulsions coated on a trans parentglass support uponexposure toa lightintensity scale for a fixed time between 1 100th and:v

1 se'eond and development for 3 minutes at 20 C. in the following developer (Ila) Hydrohui'none 'gr ams l5 Nfi'ne'thyl-p-amiriophehol Sulphate; Jibsodium sul'phite, anhydrous do 50 Potassium bromide; do' 10' Sodium hydroxide do 25 sodium tmosulph'ate, crystals do Water to 'ccs 1000 gives a transmitted density at any point along the.

logmE axis, over a range of 3.0 starting from the thresholdof the characteristic curve beginning atia density of'oirabove fogatleast 10 times the trahsmittedfde'r'isity"obtained when an identical test layerpr the emulsion is developsd for '4 minutes "at 20"C1intne' following developer (I) p'-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do 100 water-ts; c'cs 1000 the measurements of density being made at the same points on the. logmE axis, then without developing. up the latent images so formed in said emulsions to visible images treating an exposed emulsion to render it capable of forming latent image developable by the following developer (III):

Hydroquinone grams '12 N-methyl-p-aminophenol sulphate do 3 Sodium sul'phite, crystals do 90 Potassium br0inide ...v 'do- 4 sodium carbdnate, crystals do 150 Waterto 'ccs 1000 uniformly exposing. to light these-treated emulsion to produce latent image some of which'is developable by the aforesaid developer (III), developing' the uniformly fogged emulsion in -a developer whichdeve'lops the latent image which isdevelopable-by developer ('III') and-gives no more than a negligibledevelopment of the negative latent image "formed-by the original exposure compared with-the-positive-image which'isdeveloped, thenuniformly exposing to light-another of. said exposed emulsions which has also been:

treated to render 'it ca'pable of forming latent imagedevelopable by the aforesaid developer III graphic images comprising exposing to 'a lighted" object or image a photographic material comprising insep'arably" combined and extending over the same area on a single support a plurality of photographic silver halide emulsions a test layer ofany' one "of which emulsions coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /1m) and 1 second and development for 4 minutes 'at' 20 C. in the following'developer(IIb) Hydroquinone grams..- 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide -I do 4 Sodium hydroxide do 150 Sodium thiosulphate, crystal's ssrngranisw gives a transmitted density at any point alongthe logmE axis, over a range of 3.0starting frem'z.

the threshold of the characteristiccurvei=be m=- ning at a density of 0.1 above fog; at least fi timesi the transmitted density obtained when an idem tical test layer of the emulsion is developed f o'r 4 minutes at 20 C. in the following deve16p'er .(I)':

p-Hydroxyphenylglycine grams-- '10: Sodium carbonate, crystals deems... I00" Water to ccsa... 100105 the measurements of"density being made at the; same points on the l'ogioE axis, then without". developing up the latent images "so formedin'a said emulsions to visible images, treatingan'em posed emulsion to render it"capable orfiforminga latent image developable by the aforesaid"devel oper (I), uniformly exposingft'o light theiso treated emulsion'to form latent image'soine/of;

which is developable by the aforesaid developer" (I), developing the uniformly fogged em'ulsion'ir'r a developer which develops the latent image which is developable by the aforesaid'developer I')."a'n'd' gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is developed, then uniformly exposing to light another of said exposedemulsions hichhasalso been treated to render it capable of forming latent" image developable by the aforesaid developerfl) to produce latent image some of which is developable by the aforesaid developer (I), and develop-- ing the second uniformly fogged emulsion in a developer which develops the latent image which is developable by the aforesaid developer (1') and" gives no more than a negligible develb'pmentof the negative latentimage formed by the original eX-posure compared with the positive image'which is developed in said second emulsion.

4. The method of producing reversed photographic images comprising'exposing to alighted object or image a photographic material 'com'pri'sing inseparably combinedand extendingoverthe same area on a single support a plurality "of photographic silver halide emulsions a test layer of" any one of which emulsions coatedon a trans parent glass support upon exposure to alight intensity scale for a fixed time between /1m and 1 second and developmentzfor'4"minutesat 20C. in the following developer (IIb) Hydroquinone grams l2 N-methyl-p-aminophenol sulphate do 3. Sodium sulphite, crystals do 90 Potassium bromide I do 4 Sodium hydroxide .dov 1'50 Sodium thiosulphate, crystals do-.. 20 Water to I ccs-.. 1000 gives a transmitted density at'any point along the.

logmE axis, over a range of 3:0 startingifrom the.

threshold of the characteristic curve beginning :at;'

a density of 0.1 above fog; at least -10 times. the transmitted density obtained when an identicalv test layer of the emulsion is developed fo'r'4I1'ni-h utes at 20 C. in the following developer (I):

p-Hydroxyphenylglycine gramsm 10. Sodium carbonate,.crystals .do Water to ccs ..v 1000- the measurements of density being made at the same points on the logmE axis, then without developing up the latent images so formed in saidemulsions to visible image's, treating' an expo'setl Water 'tou ccs t I000 answer 13-: emulsion to render. it capable of forming latent image developable by the aforesaid developer (I) uniformly exposing to light the so-treated emulsion to form latent image some of which is developable by-the aforesaid developer (I), developing the uniformly fogged emulsion in a developer which develops the latent image which is developable by the aforesaid developer (I) and gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is developed, then uniformly exposing to light another of said exposed emulsions which has also been treated to render it capable of forming latent image developable by the aforesaid developer (I) to produce latent image some of which is developable .by the aforesaid developer (1), and developing v the second uniformly foggedemulsion in a developer which develops the latent image which is developable by the aforesaid developer (I) and gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is developed in said second emulsion.

5. The method of producing reversed photographic images comprising exposing to a lighted object or image a photographic material comprising inseparably combined and extending over the same area on a single support a plurality of photographic silver halide emulsions a test layer of any one of which emulsions coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between and 1 second and development for 3 minutes at 20 C. in the following developer (IIa):

I-Iydroquinone ..grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 50' Potassium bromide ;do. 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do; 20 Water to ccs. 1000 gives a transmitted density at any point along the logioE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals -do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Water to ccs 1000 the measurements of density being made at the same points on the logioE axis, then without developing up the latent images so formed in said exposed emulsions, treating an exposed emulsion to render it capable of forming latent image developable by the following developer (I):

p-Hydroxyphenylglycine "grams" Sodium carbonate, crystals do 100 Water to ccs 1000 uniformly exposing to light the so-treated emulsion to form latent image some of which is developable by the aforesaid developer (1), developing the uniformly fogged emulsion in a developer which develops the latent image which is developable,by-the-aforesaiddeveloper (I) and gives no more mane negligible development'ofi the negative latent image formed by the original exposure compared with the positive image which is developed, then uniformly exposing to light another of said exposed emulsions which has also been treated to render it capable of forming 1atent image developable by the aforesaid developer.(I) to produce latent image some of which is developable by the aforesaid developer (I), anddeveloping the second uniformly exposed emulsion in a developer which develops the latent image which is developable by the aforesaid developer (I) and gives no more than a negligible development of the negative latent image formed by the original exposure compared with the positive image which is developed in said second emulsion.

6. The method of producing reversed photographic images comprising exposing to a lighted object or image a photographic material comprising inseparably combined and extending over the same area on a single support a plurality of photographic silver halide emulsions a test layer of any one of which emulsions coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /100 and 1 second and development for 3 minutes at 20 C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do .50 Potassium bromide do 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do.... 20 Water to ccs 1000 gives a transmitted density at any point along the logiuE axis, over a range of 3.0 starting from the threshold of the characteristic curve begin-- ning at a density of 0.1 above fog, at least 10 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate'crystals do 150 Water'to ccs 1000,

the measurements of density being made at the same points on the logioE axis, then without developing upthe latent images so formed in said i exposed emulsions, treating an exposed emulsion to render it capable of forming latent image developable by the following developer (I) p-Hydroxyphenylglycine I "grams" 10 Sodium carbonate, crystals do Water to ccs 1000 uniformly exposing to light the so-treated emulsion to form latent image some of which is de-' velopable by the aforesaid developer (I), developing the uniformly fogged emulsion in a de-- oper (I) toproducelatent image some of which,

tographic silverhalideremulsionsea.testirlayerr oil any; one of which. emulsions? coated m transe parent glass support upon exposure toi-- a,..l-ig'ht;v intensity scale for: asfixedi time: between" vmah and: second and development; for "4 minutesxatzi 20 :6. the .followingidevel'oper. (1 b) Hydroquinone' "grams" 12; N-jinethylx-p-aminophenol"sulphate 410.... 3' Sodium'suip'hite, crystals; "60;--- '90 Potassium bromide 'do; 7 4' Sodium "carbonate; "crystals d'o' 1'50 Sodium thiosulphate, crystals do 20.v Water to 'ccs' T600.

gives a transmitted density at any point along the logmE axis; over-a range'of 3:0 starting from" the threshold of the characteristic"curve'beginning atadensity-cf-d rabove fog; atleast 5 times the transmitted density obtained when an identi ola-l test layer-of the-emulsion isd'evelopedfor 4" minutes a-t -C. in't'h-e foilowing'developjer"(III') 2 Hydroquinone grams 1 N inethyl--p-arninopheno1 sulphate ..do 3" sodium sulphi'te, crystals d'o 90 Potassium bromide do; 4

Sodium carbonate, crystals 'do "20 Water to ccs' *IQG'Of the measurements of density being made: at -the--. same points on the logioE axis, then without developing up the latent images so formed in said exposedemulsions,- treating anexposedemul'sion to render' it capableof-"forming' latent it'n'afge developable bythe follow in'g developer D- y iQ yDhenylglyeine s .grams L0 Sodium carbonate, crystals do .d- 100; Water to ccs 1000 uniformly" exposing to'lig'ht th'e 'so-treated ,e'mul sion toiorm latentimage-someiof which is dever. opa'bieby the aforesaiddeveloper (I), developing;

which developsthe latent 'iIIIfagBLWhitEh is d'lf'l'biD- able by the aforesaid developer (1) 'an'd'gives' nomore than a negligible-development of the negatiye latent image: formed by -the-. original:- exposure compared with the positive image which is developed, then uniformly exposing to light another of 'saidexposed emulsionswhiohhas also been treated' to :render 'itcapablebf forming latent imagerdeve'lopable by-the aforesaid-developer (1) to produce latent v image -some of fwh'ioh is"develop-" able by the aforesaid developer (13; arid-develop: ing the second uniiformlyi exp'osed emulsion in: a

developer-iwhich developsthe latent :imagewhich:

isr'deveiopa'ble by the aforesaid developer" (2B and gives. no. more? than; aJnegIigi'bI-e. development- "of: ther regaitive latent image iformed by theiori'g inal' exposure compared withith'e :positive'iimage2wni'eh is developed int-said'isecon'd emulsion.

- 8. The: method ofvproduc'ingiiteversed i photm graphic images: comprising exposmgitdta lighted: 7515 objeetForrhi raw:1a;photmgraphicnmarteria1 comprise: in'g inseparabiy 'combinedand iextendingroveit thev same larea oni arsingle support aapiuraflity:ofiplriotograp'hic :si-iver halide =emulsionseaitestalayeri of: anyone-10f whioh 'emulsionsrrc'oated' on a" trans parent glass 1 support 'up'orr exposures. :to. "a.- light intensity scalie foriafixedatime between th and? 112sec'ondvandlldevelopmentrm-:4 minutes at 20 'C. inzthernfoliowing:developer' (IIbi) Hydroquinone "grams" I2 N methyhp 'aminophenoi sulphate d'o '3'; Sodium sul'phi'te; crystals 'd'o '90 Potassium bromide -do. 4: sofdiu'mmarbonate crystals.' do I50; Sod'ium 'th'iosulphat'e; crystals do 201" Water'to' 'cos 10'0'0 givesa-t-ransmitted :densitywat'any. point aiongs the: 10gifoE-./axis,= over a range of Btu-starting: from the; threshold-of thencharacteristiccurve be'g'in-ning: at. a..;c,le nsityv of 0.1 abovefog, at lea'stam times the: transmitted density obtained when: an-aidenticals test layer (lithe-emulsion isz'developed for-min,

utes at 20 C. in-t'heofollowingdeveloper:(my:

Hydr'oquinone "grams". '12 N methyl 'p aminopn'enols ulphate do; 8* Sodium suiphiteporyst'als' ;do 9U Potassium"-bromide id'o- '4 Sodium carbonate; crystals do 20 Water to ='ccs 1091):

the measurements of dens'ity being-ymadeaatzthe. same points o'mthe llogiioE axis, then" without;

devel'opingiup the'l'atentimages so formed in said exposed emulsions; treating an: exposed emulsion to rendri'tcapable of forming latentimagedevel opabie by the following developerKI) uniformly exposing to lig httheiso -treaited eimi'l sion toformllatentiimazgei'some of which is :dvelopable by the. aforesaiddevelopen -(I)v,-developing' the uniformly. fogged emuisiorrnin..avdeveloper.

which develops the :1 atom image. whichli's develope abie 'byth'e aforesaid-developer.(1). andgjives not more-than a inegl'igibie. development dfl the mega. ti've latent'image' formed-"by the originalrexposure A compare'dLwith the positive imagewhic'h is-deveb oped' then uniformly 'exposingitoll igfit.another oft said exposed emulsions which has also been; treated to render it capable of forming latent image developablebytha aforesaid c ieweloper (1) r to produceiiatentrimage some ofw hioh i'sdeVlbp able by. theraforesaid developer: (I7 'an'd deyelop-' ing the. seconduuniformly exposedxemulsion in 'a' developer. .which develops itheslatent'iim'a'ge *W ch isrdevelopahlenby theaforesaid developer- 61) and gives no morethan anegligibledevelopment ofthejn egatiye '1 aterit image formed by "the original exposure-'compared-'withthe positivezimage whiz-iii is d'e'vloped' in said seoon'd emulsion;

' {EDWARD BO'WES KNOT'IY."

A GUYW'I'LLIAM WIIJJSLSTEVENS;

BEFERENCES GIT:ED

:The following references are of recordinwher file" 'of'this patent:

UNITED sTATEstPATENrs Number Name I Date" t omemerei-eneewnwnmniaz man Kodak 00., Rochester, New York, 1927; pages OTHER REFERENCES 15, 20, 22, 2s, 30, 31, 4'1, 48, 50, 52, 72, 73, 80-85. Mees, The Theory of the Photographic Proc- (Copy in Div. 67.) ess, published by the Macmillan Co., New York, Wall, Photographic Emulsions, published by 1942, Pages 294-297 and 5 American Phot. Publ. Co., Boston, 1929; pages 52, (Copy in Div. 67.) 53 and 135-137. (Copy in Div. 67.)

Bullock, Chemical Reactions of The Photographic Latena Image, vol. I; published by East- Certificate of Correction Patent No. 2,456,954. December 21, 1948,

EDWARD BOWES KNOTT ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 61, claim 3, for the Words which on read which one; column 7, line- 26, for exposed reed expose; line 72, for given read giving; column 11, line 18, for 20 C. read 20 0.;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 26th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.