US2456956A - Photographic processes and lightsensitive elements therefor - Google Patents

Description

Dec. 21, 1948. KNOTT r AL 2,456,956

' PHOTOGRAPHIG PROCESSES AND LIGHT-SENSITIVE ELEMENTS THEREFOR Filed Aug. 1, 1947 OBJECT Q4) LA YEK OF HIGH GRAD/1 TION EMULSION I wH/c'H FORMS LATENT [241,465 MOSTLY INS/DETHE SILVER A IDE GRA/NS \M/LAYER oFLow GRADATION EMULSION WHICH FORMS SURFACE LATENT IMAGE,

THE EMULSION HAVING A THRESHOLD SPEED EQUAL T0 ORLOWEK THAN THAT OF THE ABOVE EMULSION SUPPORT EXPOSE TOIJG'HTED OBJECT LA YEI? OF HIGH G'KADAT/ON EMULSION -CONT4ININ6 NEGATIVE LATENT IMAGE MOSTLY INSIDE THE J/L v51? HAL IDE elm/Ms LAYER OFLOW GRADATION EMULSION com/1 IN/NG NEGATIVE LATENT IMAGE o/v SURFACE OF .SIL vck HAL/DE GRAINS DEVELOP IN DEVELOPER WHICH DEVELOP IN DEVELOPER DEVELOPS INTZ'RNAL LATENT IMAGE WHICH DEVELOPJ JUBSTANTIALLY ONLY LAYER or HIGH GRAD/lT/ON EMULSION CONTAINING NEGATIVE LATENT IMAGE M05727 INSIDE SILVER HAL/DE GR'A IN5 NEGATIVE IMAGE OF HIGH CONTRHST SUPPORT JUPPORT DEVELOP IN DEVELOPER WHICH DEVELOPJ /NTERNAL LATENT [MAGE NEGATIVE IMAGE'OF HIGH CONTRAST EDWARD BOWES KNOTT GUY WILLMM .WILLIS STEVENS INVENTORS SUPPORT fiMVJJ J ATTOR EYS it has a higher tendency to aerial oxidation and to give fog.

Whilein this specification we have described our invention partly in regard to a theory of in ternal 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 fpresent invention employs the following types of emulsions:

TYPE I These are the emulsions which will develop,

(afterexposure) in internal developers of the kind given in atleast one of the Formulae II(a.) and II(b), but will not develop in Formula III or in Forula I.

(1) Normal Range of Exposures veloped in the internal developer Formula II(a) the transmitted density obtained at any point a density range of 3.0

along the IOgroE axis over starting from the threshold of the curve (D=0.1 above fog), should be at least 5 times, and preferably at least times the transmitted density obtained when an identical test layer of the emulsion is developed with the surface developer of Formula I or preferably III, the measurements being made at the corresponding (is. same) points on the logioEaxis; as indicated, the best (i.e. preferred) emulsions are those giving 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 rigid requirement, for instance for making a tone correcting mask, but'it is sufficient if in the above test the upper limit of 3.1 is substituted by an upper limit of 1.0.

TYPE II These are the emulsions which when exposed to a light intensity scale, the whole of which is exposed for some fixed time betweeen /100 and 1 second, will develop normally in Formulae I and III as well as in Formulae II(a) and II (b) As measured according to normal photographic testing technique, when a test layer of the emulsion is coated on a transparent support (e. g. glass) and the layer is exposed to a light intensity scale the whole of which is exposed for some fixed time between /100 and 1 second and is developed in the internal developer 11th), the transmitted density obtained at any point along the logmE axis of the curve between the density range of 0 to 3.0, preferably 0 to 2.0, does not exceed the transmitted density obtained when an identical test layer of the emulsion is developed in Formula III, the measurements of density being made at the same points on the logmE axis of the curve. Most known sensitive materials comprising a gelatino silver halide emulsion fall in the category of Type II.

,Since Formula III contains sodium sulphite and Formula I is free from sulphite, and sulphite develop or only slightly is known to have some solvent action on silver chloride and bromide (although very little on silver iodide), it is apparent that when making any of the above measurements on an emulsion to obtain, with a high degree of precision, information on the amount of surface latent image given by such emulsion, it is important to use Formula I. As will be apparent hereinafter, in performing the invention a small amount of development of the internal latent image is of no real consequence for practical purposes, it may be advisable to employ Formula III, since this developer is not only less liable to aerial oxidation but gives better density in the image produced by the development of the Type II emulsion.

It is to be noted that an internal developer is necessarily capable of developing not only. a latent image inside grains but also of developing a latent image on the surface of grains (whether such grains contain internal latent image or not) and also of carrying on the development of a surface latent image which has previously been only partly developed. 1

It is also to be noted that where a ,surface developer is employed to develop a surface latent image, then all grains which are therebyfully developed cannot be subsequently developedatall in an internal developer. 1

According to one feature of the present'inv'en tion there is provided the method of selectively producing images in a photographic material comprising silver salt emulsions on a single support which comprises employing therefor two emulsions one of which is Type Ias herein de-. fined and the other of which is of Type II as herein defined, selectively exposing (simultaneously or consecutively) both emulsions to'form latent images therein and differentially developing the latent images so formed. o,

In this form of the invention thedifierential development may be performed by treating the whole material in a, developer which develops practically only surface latent image (preferably to completion) and then treating the whole material with a developer which develops internal latent image.

The present invention also provides a useful sensitive photographic material comprising on a single support two sensitive silver salt emulsions one of which upon exposure forms the latentimage mostly inside the grains as defined by Type I above and the other of which upon exposure forms a surface latent image as defined by Type II above, the combination beingsuch that each of such emulsions can be selectively exposed,

According to a modification of the invention; there is provided the method of producing anurnber of prints of differing gradations (germ-- mas) wherein each of the prints is madeby exposure of a sensitive material comprising on"=a, single support two silver salt emulsions givingv different gammas, one of which is of Type I as herein defined and the other of which is of Type II as herein defined and Wise that the emulsions of Type I and II are dif ferently developed from print to print,

The invention contrast wherein such image is formed by ex-- posure of a sensitive material comprising one two silver salt emulsions giving differing gammas, one of which is of TypeI as and the other of which is of Type II as herein defined, and the material is developed the latent images so. formed in the various prints are developed insuch also provides the method of pro-; ducing a photographic image of a predetermined;

in a developer whose capabilities of developing internal and surface latent image are so related as to give the saidcontrast.

The invention includes a sensitive material for this purpose and comprising ona single support, two sensitive silver salternulsions, either as superimposed or side by side layers or mixed, one of which is of Type I (as herein defined) and upon development thereof gives an image of one gamma and the other of which is of Type II (as herein defined) and upon development thereof gives an image of a different gamma.

For some purposes such a sensitive material is useful for producing two photographic images on a single support by exposing the matrial and then after treating the whole material in a developer which develops practically only the surface latent image or images, the whole material is treated with a developer which develops the internal latent image.

Whenever it is desired that several emulsions on the same support can each be selectively exposed, (i. e. simultaneously or consecutively) this can be done by several known methods, for instance,

to) Making the emulsions differentially colour sensitive,

(b) If the emulsions are in superimposed layers, placing a light absorbing filter layer between them -:or one of them such as in theType emulsion,

te It the emulsions :are side by .side (1. e. in different areas of the support) they can be easily exposed separately.

Possible ways of arranging .a-niemulsion of Type I and an emulsion :of 'Type II .in'the present ins/ention 'are illustrated by the tollowing;

'(l) A not specially ico'lour sensitised emulsion of 'Type I -having a relatively high zblue sensitivity mixed with or superimposed on a green :or red sensitised emulsion of "Type II :of relatively low blue sensitivity.

"(#2) A green sensitiueemulsion ofilype Ianixed or superimposed .on a :red sensitive emulsion of Type II.

(3') not specially (colour. sensitised emulsion .of Type I coated on a not specially :colour .sensitised emulsion of Type II .with .a blue absorbing filter layer .therebetween, "or thefilteringmateri-al may be in one :of the emulsions .sunhas an the Type I emulsion. finch emulsions-can :be on the same side or =.opposite :sides of the support.

(41) A Type I emulsion, colour iSEHSLfiSEdiOI' not and :a Type II emulsion, colour sensitised zen-mot, coated :side .by. side (i. .e. in :diiterent :areas 0f the support).

The invention is :not limited to these specific ways which are jgiveniby way of .exampleionly.

We have found that 11a iuseful anultiwcolour ph a h process and sensitive material for ruse therein mesultsif there isiemployed on .-'a:sing1e support two emulsions mespeotivelyof Typesl and II, the combination being suehthatrtheylareeffecetively -.difier.entially colour. sensitive.

f'llhe following Example illustrates-a material whichrcan berempl'oyed as atwo colour element in a thE-GBCOIOUILDHOCBSS- EXAMPLE I 1 03,5100 cos. of 'an emulsion .of TypeI (which has not been specially colour sensitised) .containing the silver .halide equivalent of 20.0 grams of .silver nitrate .there is added .200 cos. ,ofI-an 8% alcoholicsolution .of hydrolysedsoft .lac resin (tor such resins'see ,U. S. ,RatentNo. 12,199,973). To 300 cos. of a Type JI=s1lver -chloride emul- "be coated as superimposed layers.

:sicn containing the silver chloride equivalent to grams of silver nitrate and sensitised to green 'by addition of cos. of a 0.02% alcoholic solution of the dye 5-'[(2-ethyl-1(zlbenzoxazolylidene) ethyl-idene] 3-n-heptyl-l-phenyl-Z-thiohydantoin) (Example '3 of U. S, Patent No. 2,- 282,116) there is added 60 cos. of an 8% of alco- 'holic'solution of the said hydrolysed soft lac resin. The two emulsions are then mixed at 30 C. and coated on a support such as paper, or they may After exposure to a colour image or object this material can be processed. to give a two-colour negative image by treating it as follows:

('1' Treat in an ordinary surface colour developer containing a colour coupler which gives a magenta coloured image, for a time sufiicient to colour develop the surface latent image in the TypeII emulsion.

("2") After washing, develop in a developer containing a coupler giving an orange coloured image such developer containing also a silver halide solvent, such as 5 to 40 grams per litre of sodium thiosulph-ate, so as to develop the in ternal latent image in the Type I emulsion.

(3") After washing dissolveout allsilver formed and all unused silver halides in a bath of sodium .thiosulphate and potassium ferricyanide.

This example couldobviously be applied to the processing of a two-colour element in a two- .colour process if the coupler which gives magenta is replaced'by one givingblue-green.

Selective developability depending on 'laten image distribution may also be usefully combined with known means .(see for example U. S. Patent Nos. 2,23.-1;684 and2,226,639) for obtaining selec- -t-ive developab,ility. For instance in a subtractive process of three-colour photography, silver bromide or iodo-bromide emulsion of Type II may :be mixed with a silver bromide or iodobromide emulsion of Type I and a silverchloride emulsion of Type II; alternatively, ithese iemulsions may be coated in three superimposed .latyersor in two superimposed layers one of which consists of ,a mixture of two of the emulsions.

After exposure of such material the silver chloride +emulsionmay be selectively developed before the other emulsions {are separately developed in accordance with their (type. Of course, any two super-imposed emulsion layers :both of the same type can .be selectively processed in known manner, such as .by employing loaded developing solutions as described in U. S. Patent .No. 2,059,884, a third emulsion of the other type being mixed in one of such layers.

Protective layers which are only penetrated by suitable acid or .a1kaline solutions may also be used in the same way The following illustrates "a three-colour process:-

EXAMPLE II On 'a support, there is first coated a silver bromide 01' iodobromide emulsion of Type sensitised to the red with, for instance, 3;3-di- .il'IlEthYl-Q: 5 :4 :5 -dibenzthiacarbocyanine iodide.

considerably the effective blue sensitivity of the red sensitive layer. The blue sensitivityrof the silver chloride emulsion is so low that there is practically no image formed therein when the blue sensitive emulsion mixed therewith is properly exposed. This mixture may be made exactly as the mixture prescribed in Example I. The two emulsions of the mixture may if desired be coated on superimposed layers. Alternatively, the blue sensitive emulsion can be coated by itself as a layer over a layer consisting of a mixtureof the red and green sensitive emulsions and the blue sensitivity of the latter can be effectively reduced in known manner by interposing a yellow filter layer between the layers as described in British Patent No. 500,611.

After exposure of the material to a coloured object or image, it is processed as follows: i

(1) Treat in a mildly acting first developer containing a colour coupler which gives a magenta coloured image, for a time just sufficient to colour develop the surface latent image in the silver chloride emulsion without having any practical effect on the silver bromide (see for instance U. S. Patents Nos. 2,226,639 and 2,231,684).

The mildly acting first developer just referred to is composed as follows: I

Water liters 1 Diethyl para-phenylene diamine I-ICl grams Sodium sulphite do 5 Sodium carbonate do Potassium bromide (Molar solution) cc s 2 with the addition of the coupler.

(2) After washing, develop in a surface developer containing a coupler giving a blue-green coloured image for suflicient time to develop only but completely the surface latent image in the lower red sensitive emulsion layer (Type II emulsion).

(3) After again washing, develop in a developer containing a coupler giving a yellow coloured image, such developer containing also a silver solvent, such as 5 to 40 grams per liter of sodium thiosulphate, so as to develop the internal latent image in the silver bromide or iodobromide emulsion (Type I) in the upper layer.

(4) After washing dissolve out all silver formed and all unused silver halides in a bath ofsodium thiosulphate and potassium ferricyanide.

' -A less advantageous form of the invention is illustrated by the following example:

EXAMPLE III Potassium dichromate grams 12 Sulphuric acid (conc.) ccs 12 Water to make ccs 1000 Itis then washed for 5 minutes in running water, and then treated for 2 minutes at 70" F. in:

Sodium bicarbonate grams 50 Water to make ccs 10001 a final thirty minutes washing is then given and I the layer is dried.

This treatment converts the process emulsion from Type II to Type I. The other side of the film is then successively coated with a blue absorbing filter layer and then an emulsion 'ofType II. This material can be used in a two colour process asa printing material where it is desired to expose both emulsions prior to any processing step.

Other examples of theuse and selective treatment of emulsions of different types on a single support are as follows; and in these examples the emulsions may be also differentially colour sen;- sitised so that they can be exposed selectively by different coloured lights.

(a) Side by side stereoscopic images (i. e. on different areas of thesupport) produced on the same cinematograph film which areto be developed to red and green respectively (for viewing through red and green spectacles) maybe processed in a simple manner by treatment of the Whole film first with a developing solution for developing only one of the emulsions and subsequently with a developing solution for developing the other emulsion.

(b) A picture image and a sound track image side by side on the same support can be. developed separately for instance to different gammas, without the trouble of applying the development solutions to the separate picture and sound areas of the cinematograph film (e. g. by applicator rollers) by employing (e. g. in admixture) an emulsion of one type for printing the sound track and an emulsion oremulsions of the other type for printing the picture.

(0) Where it may be desirable to develop the two longitudinal halves of 16 mm. film separately, for example, one half to black and white and the other half to a coloured image for any purpose; this can be done by adopting a procedure analogous to that indicated in (a) and (b).

Although the invention which has been described in detail above requires that the emulsions of Types I and II should be so constituted or arranged that either of them can be selectively exposed, it is possible as has already been indicated 'to modify the invention by dispensing with this requirement and making the emulsions of the said two types so that they give different gammas and then-such a material, although less useful than those previously described, can be used for so-called multi-contrast purposes, such as for producing images of different contrasts from negatives of the'same contrast or images of the same contrast from negatives of different contrasts; for such purposes it is usually desirable that the gammas should differ by at least 2.5, and the low gamma being not more than 1.8, such gammas being measured as set forth in British Patent No. 541,510, it being understood that the appropriate'developers of Formula 11(1)) and III are used for developing the Type I and Type II emulsions respectively.

The emulsions can be dye-sensitised or not. As an example we can employ an emulsion of Type II giving a low gradation in Formula III and an emulsion of Type I giving a high gradation in Formula II(b). In this combination the threshold speed of Type II emulsion when developed in developer Formula II or III should for example be higher than that of Type I emulsion when developed in developer Formula 11(1)) preferably the characteristic curves under these conditions' should cross at about a density of one. The emulsion giving the higher gradation (gamma) can be made as the emulsion described in Example III herein; preferably the fine grain process type emulsion used should be one of good uniform grain size and giving a gamma of about 4. The other emulsion can be one of Type 11 giving a gradation of 1.2.

The material so made can be printed with white light and then the contrast of the image controlled by choice of the developer. For example, using an emulsion of Type II giving a low gradation in Formula III and an emulsion of Type I giving a high gradation in Formula 11(1)) and still higher in Formula II(a), the image will be of relatively low contrast if developed in a developersuch as Formula III, of relatively medium contrast in a developer of Formula 11(1)) or a higher contrast in Formula II(a). Using either Formula II(a) or II(b) a higher contrast can be obtained if before development the exposed material is first treated in a mild silver oxidising bath which destroys the surface latent image in the emulsion of Type II.

Two examples of such solutions are the following solutions A and B.

As another example, the threshold speed of the Type II emulsion can be equal to or lower than 3 that of the Type I emulsion. Such a material gives low contrast mainly due to the Type II emulsion on development in Formula III and a highcontrast mainly due to the Type 1 emulsion on development in Formula II(a) or'II(b).

As has previously been indicated material of this kind employing emulsions of Types I and II having different gammas may be. processed: also by treating the whole material after exposure in a developer-which develops practically only the surface latentimage. .or images, and thereafter treating the whole material in a" developer whichdevelops the internal latent image.

This application is a continuation in part of our co-pending application Serial No. 528,738, filed March 30, 1944, now abandoned.

The accompanying drawing is a flow-diagram of-one embodiment of our invention and shows the operation: of the process. .At-B is shown a support coated with a layer of a low gradation.

(contrast) emulsion which forms latent image on the surface of the silver. halide grains andhas a threshold speed equal to or lower than the threshold speed of a second layer of emulsion coated upon the low gradation emulsion layer,

said second emulsion layer consisting of a high gradation emulsion which forms the latent image mostly. inside the silverhalide grains. Upon exposing. this photographic element to the lighted object shown at A, negative latent image isv formed in both emulsion layers as shown at C. Upon developing the exposed photographic ele-'- ment shown. at C in a developer which develops substantially only surface latent image, the latent image in the lower emulsion layer is developed. to ajnegative image-of low contrast while the negative latent image in the upper layer is substantially unaffected as shown at D. At this point, the photographic element shown at D can be fixed and washed, or the elementcan be developed 10 in a developer which develops internal latent image, whereupon the negative latent image in, the upper emulsion layer is also developedgivi-ngj a negative image of high contrast as-shown at E. The exposed photographic element shown at (3, 11 developed in a developer which develops internal latent image, gives a negative image in both emulsion layers, the overall image being of high contrast as shown at F.

What we claim as our invention and desireto besecured by Letters Patent of the United States is:

l. A method of selectively producing photographic images in a photographic element con-q taining, ins'eparably combined and extending over the same area on a single support, a light-sensi tive silver salt photographic emulsion (I) a test" layer of which coated on a transparent support:

and the layer exposed to a light intensity scale" for a fixed time between and 1 second and development for 3 minutes at 20 C. in'the fo'I-" lowing developer (Ila):

Hydroq-uinone grams N-methyl-p-aminophenol sulphate -do- 15 Sodium sulphite, anhydrousuhufldmanz 50 Potassium bromide oV .i d0; 10 Sodium hydroxide do 1 .25 Sodium thiosulphate, crystals do 20 Water to ccs '1000 gives a transmitted density at any point along the logioE axis over a density range of 3.0 starting. from the threshold of the characteristic-- curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for iminutes at 20 C. in'the following developer (I) p-hydroxyphenylglycine grams-- 10 Sodium carbonate, crystals do 100 Water to ces 1000 Hydroquinone grams- N-methyl-p-aminophenol sulphate' do- J Sodium sulphite, crystals do i 90- Potassium bromide do- 4 Sodium carbonate, crystals do' T Sodium thiosulphate, crystals do 20' 5 Water to. ccs' 1000 gives a transmitted density between the range of" 0 to 2,0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C, inthe followingdeveloper (III) Hydroquinone I grams 1 2 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals; do- 90 Potassium bromide 1o 4 Sodium carbonate, crystals -do- 150" Water to ccs 1000 comprising exposing each emulsionto light, H1611:

treating the whole element with a deve1operwhich develops substantially only the latentv image which is developable by developer (III) and then developing'the whole element in a dc: veloper which develops the latent image which is.

developable in developer (II'a).

Hydroquinone grams 15 N- methylp-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 gives a transmitted density at any point along the logioE axis over a density range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.10 above fog, at least times the transmitted density obtained when an identical test layer emulsion is developed for 4 minutes at 20 C. in the following developer (I):

p l-lydroxyphenylglycine grams Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements being made at the same points on the logioE axis, and another light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer is exposed to a light intensity scale, for a fixed time between /100 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 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) 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 comprising exposing each emulsion to light, then treating the whole element with a developer which develops substantially only the latent image which is developable by developer (III) and then developing the whole element in a dedevelopable in developer (Ila).

{3. A method of selectively producing photographic images in a photographic element containing, 'inseparably combined and extending over the same area on a single support, a lightsensitive silver halide emulsion (I) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between /ioo and 1 second and de velopment for 3 minutes at 20 C. in the follow' ing developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate clo 15 Sodium sulphite, anhydrous do '50 Potassium bromide zlo 10 Sodium hydroxide do 1 25 Sodium thiosulphate, crystals do j 20 Water to ccs 1000 gives a transmitted density at any point along the logmE axis over a density range of 3.0 start-j ing from 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 identical test layer of the emulsion is devell oped for 4 minutes at 20 C. in the following developer (I):

p-I-Iydroxyphenylglycine grams '10 Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements being made at the same points on the loginE axis, and another light sensitive silver-halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity for a fixed time between i and 1 second and development for 4 minutes at 20 C. in the fol-' lowing developer (IIb) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do '90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 "c5 veloper which develops the latent image which gives a transmitted density between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) 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 a 4 Sodium carbonate, crystals do Water to ccs 1000 comprising exposing each emulsion to light, then treating the whole element with a developer which develops substantially only the latent image which is developable by developer (III) and then developing the whole element in a developer which develops the latent image which is developable in developer (Ila).

4. A method of selectively producing photographic images in a photographic element containing, inseparably combined and extending over the same area on a single support, a light sensitive silver halide emulsion (I) a test layer oiwhich coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between i 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 90 Potassium bromide do 4 Sodium carbonate, crystals do 150. Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the log oE-axis over a density range of 3.0 startscale 113 ingfrom: the threshold of the characteristic curve beginningat 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 90 Potassium bromide ..do 4 Sodium carbonate, crystals -do 150 Water to ccs 1000 the measurements being made at the same points on the logmE axis, and another light sensitive silver halide photographic emulsion (II) a test layerof which coated on a transparent support and the layer exposed to a light intensity scale for; a fixed time between 1 and 1 secondand development for 4 minutes at 20 C. in the aforesaid developer (IIb) gives a transmitted density between the range of 0 to 2.0, which does not ex. ceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the aforesaid developer (III) comprising exposing each emulsion to light, then treating the whole element with a developer which develops substantially only the latent image which is developable by developer (III) and then developing the whole element in a developer which develops the latent image which is developablein developer (11b).

5. A sensitive photographic element comprising, inseparably combined and extending over the same area on a single support, a light sensitive silver salt emulsion (I) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for-a fixed time between 5 and 1 second and development for 3 minutes at C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do l 50 Potassium bromide .1do 1 10 Sodium hydroxide s do Sodium thi osulphate, crystals do h 20 lIVater to ccs 1000 gives a transmitted density at any point along the IOglOE axis over a density range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fo'g, at. least 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-l-lydroxyphenylglycine grams 10 Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements of. density being" made at the same points onthe logi'oE axis,v andanother light sensitive silver salt photographic emulsion (11) a test layer of which coated on a transparent support and the layer exposed to a. light" intensity scale for a fixed time between and 1 second and development for 4 minutes at20 C; in the: following developer (11b):

Hydroquinone "grams" 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate, crystals "do..-" 150 Sodium thiosulphate, crystals dc 20 W ter to -ccs 1000*- 7 between 7100 and 1' second and development "for" gives-a-- transmitted. density between. the: of 0 to 2.0, which does not exceed the transmitted. density obtained when an identical test layer of the emulsion- (II) is developed for 4 minutesat 20 C. in thefollowing developer (III):

6. A sensitivephotographic element comprising; inseparably' combined and extending over the same area on a single support; a light sensitive silver halide emulsion (I), a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between V and 1 second and development for 3 minutes at 20 C. in the following developer (II'a):

Hydroquinone gramss 15" N-methyl-p-aminophenol sulphate do 15.

Sodium sulphite, anhydrous .do 50 Potassium bromide do 1'0" 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 density range of 3.0,

starting from the threshold of the characteristic curve beginning at a density of 0.1 above feg, at' least 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 the measurements of density being made at the same points on the logioE axis,v and anoth'er li'ght' sensitive silverv halide photographic emulsion (II).

a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for. a. fixed; time between l/lo'o and I second and development for 4 minutes at 20 (3 inthez;

following developer (IIb):

gives a tr-ansmitted'density between the range ot 0 'to 2.'0; which does not exceed the transmitted density obtained when an identical test la'yer' of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone w engrams.' 12. N-methyl-p-aminophenol sulphate do- 3- .Sodium sulphite, crystals -do Potassium bromide do t 4: Sodium carbonate, crystals do Water to ccs- 1000.

7. A sensitive photographic element comprising insep'arably combined and extending over the same area on a single support,v a light sensitivesi'lve'r halide emulsion (I) atest layenofwhich coated on a transparent support and the layerexposed' to a light intensity scale for a fixed time ranger QAGGXQBG fiininutes' at C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15- Sodium sulphite, anhydrous do 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 density range of 3.0 starting from 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 identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (I) p-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do 100' Water to ccs 1000 p the measurements of density being made at the same points on the logioE axis, and another light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between 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 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density between the range of 0.to 2.0, which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

I-I'ydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulp'hite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Water to ccs 1000 8. A sensitive photographic element comprising, inseparably combined and extending over the same area on a single support, a light sensitive silver halide emulsion (I) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between /ioo and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

veloped 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 s- 150 Water to ccs 1000 Hydroquinone grams N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate, crystals do- 150 Sodium thiosulphate, crystals d0 20 1000 Water to ccs.'

gives a transmitted density at any point along the logmE axis, over a density range of 3.0 startingfromthe threshold of the characteristic curve beginning. 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 .de-.

the measurements being made at the same points on the logioE axis, and another light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between and 1 second and development for 4 minutesat 20 C. in the aforesaid developer (IIb) gives a transmitted density between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed'for 4 minutes at 20 C. inthe aforesaid developer (III).

9. A sensitive photographic element comprising vtwcinseparably superposed emulsion layers.

extending over the same area on a single support, one emulsion layer being .a light sensitive silver halide photographic emulsion (I) a test layer-of:

which coated on atransparent support and the layer exposed to alight intensity scale for a fixed time between /100 and 1 second and development for 3 minutes at 20 C. in the following developer (IIa) Hydrcquinone 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 lc-gioE axis over a density rangeof 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least same" points on the logioE axis, and the otheremulsion layer bein a light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between /100 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 d0 '90 Potassium bromide do 4 Sodium carbonate, crystals sdo Sodium thiosulphate, crystals do r 20 1000 Water to ccs gives a transmitted density below the range of 0 to 2.0,: which does not exceed the transmitted density obtained when an identical test layer of 17 the emulsion (II) 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 10. A sensitive photographic element comprising two inseparably superposed differentially color sensitive emulsion layers extending over the same area on a single support, one emulsion layer being a light sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent support and the layer exposed 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 (Eu) 1 Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do Potassium bromide do Sodium hydroxide do 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the 10gl0E axis over a density range of 3.0 starting from 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 identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (I):

20 C. in the following developer (Ila) Hydroquinone grams N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 50 Potassium bromide do 10 Sodium hydroxide do rr 25 Sodium thiosulphate, crystals -do Water to ccs 1000 p-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements of density being made at the same points on the logioE axis, and the other emulsion layer being a light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between /100 and 1 second and development for 4 minutes at 20 C. in the following developer Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do- 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density between the range of 0 to 2.0, starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) 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 os 1000 gives a transmitted density at any point along the logioE axis over a density range of 3.0 starting from 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 identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer(I) p-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do Water to ccs 1000 the measurements of density being made at the same points on the logmE axis, and the other two emulsion layers being each a light sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent support and the layer exposed to a light intensity scale for a fixed time between /100 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

Hydroquinone grams 12 N-methyl-p-aminophen0l sulphate do 3 Sodium sulphite, crystals 'do 90 Potassium bromide do 4 Sodium carbonate, crystals do- Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density between the range of 0 to 2.0, which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

I-I-ydroquinone 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 EDWARD BOWES KNO'IT. GUY WILLIAM WILLIS STEVENS.

No references cited.

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