Title:
Photographic reversal processes
United States Patent 2456954
Abstract:
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...


Inventors:
Bowes, Knott Edward
Willis, Stevens Guy William
Application Number:
US76563347A
Publication Date:
12/21/1948
Filing Date:
08/01/1947
Assignee:
EASTMAN KODAK CO
Primary Class:
Other Classes:
430/378, 430/383
International Classes:
G03C5/50; G03C7/30
View Patent Images:
US Patent References:
Description:

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 while 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 Wall's "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 iodobromide 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__ 12 Cone. sulphuric acid ---_------ ccs__ 12 Water ------------------------ ccs 1000 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 3 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 carbonate (cryst.) --------do-. 100 Water to ----------------------- ccs- 1000 Development time 4 minutes at 200 C.

FORMULA II (a) 50 "INTERNAL" DEVELOPER Sodium hydroxide ----------grams---- 25 Sodium thiosulphate cryst. --------do--- 20 Water to ___ ___ __ _____ccs_ 1000 Development time 3 minutes at 20° C.

FORMULA II (b) "INTERNAI" DEVELOPER Hydroquinone -- --------- grams-N-methyl-p-aminophenol sulphate-do---Sodium sulphite (cryst.) -------doPotassium bromide ---------------do -Sodium carbonate (cryst.) -------- do-.-Sodium thiosuiphate --------------do Water to ------------------------ccs-Development time 4 minutes at 200 C.

FORMULA III COIMMERCIAL DEVELOPER This is the same as 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 of Formulae II (a) and II (b), but will not develop or only slightly develop in Formula III or in Formula I.

(1) Normal range ofexposure 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 /'0ooth and 1 second and is developed in the internal developer II (a) the transmitted density obtained at any point along the logloE axis over a range of 3.0 starting from the threshold of the curve (D=0.1 above fog) should be at least 5 times, and preferably at least 10 times, the transmitted density obtained when an identical test layer of the .emulsion is developed with the surface developer of Formula I or III, the measurements of density being made at the corresponding (i. e. the same) points on the logloE axis; 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 o10.

SSince Formula III contains sodium sulphite and Formula I-is free from sulphite,i and sulphite 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.

The reversal urocess of the nresent invention depends upon the fact that the type of emulsion 10 defined 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 capable of forming surface latent image on exposure. The treatment depends to some ex- t.e.nt. ir -unn ho t nertirPnlaTr emulsion ExIavomnIoo nff Ssuch 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 em20 ploying an organic developing agent and which has little or no solvent action on the silver halide. (2) In the case of some emulsions of the type defined which are colour sensitised, the treatment can be with plain water alone.

25 The effect of any such treatment or any similar treatment for the same purpose can be ascertained by taking an unexposed layer of the emulsion and merely giving it the treatment and then subjecting it to an image-wise exposure and if 30 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 35 photographic images comprising -exposing to a lighted object or image a photographic material comprising on a single support a plurality of photographic silver salt emulsions of the type herein-defined, then without developing up the 40 latent images so formed in said emu'sions, treating at least one of said exposed emulsions to render it capable of forming surface latent image, i. e. latent image developable by the developer of. Formulae I or III, and then while continuing 45 the treatment or after the treatment, uniformly exposing to light the so-treated emulsion to produce latent image some of which is developable by the aforesaid developer I or III, developing the uniformly fogged emulsion in a developer which 50 develops the latent image which is developable by developer 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 55 uniformly exposing to light another of said exposed emulsions which has also been treated (simultaneously with the first-mentioned emulsion or by a separate treatment) to render it capable of forming latent image developable by 60 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 65 by developer 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 in said second emulsion. The unused silver salt may 70 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 75 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 sufficient 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 image is usually obtained by employing for the first image-forming exposure an over-exposure which can be ascertained by a test or series of tests giving different exposures and development of the latent image in a developer such as Formula 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 treating 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 would 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 developing activity is very small.

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

N-methyl-p-aminophenol sulphategrams-_ 10 Sodium sulphite, cryst. _----------do -- 100 Water to 1---------------------- ccs__ 1000 Hydroquinone -----,- ------_ - grams_Sodium sulphite, cryst. -_--------do ___ Sodium metaborate --------------do-... Water to --..----.. -- --------------ccs_ 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 6 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-ethyl1(2) benzoxazolylidene) ethylidene - 3-n-heptyl1-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 in,20 vention of producing reversed images is that such type of emulsion can be made to have a higher 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 on a 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 determined in known manner, for example: 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.

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.

t5 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 employing three of the kind of emulsion in question. This advantage can be seen by considering the case of two superimposed emulsion layers one being for example red sensitive and the other being for exa:gple ro'en:lsennsitive. The :steps relquired to rodu~re reversed images-if both emulsions are of0 the sametype are as follows: 'ailDi'NA'aY gU'IFACE LATENT. IMAGiE'FORMING TYPE :A:red sensitised emulsion of this type coated aver a;green sensitised emulsion bf the same type.

After-exposure the processing normally is: 1. :Develop-both layers.

2. Wash.

:3. Expose the one layer uniformly to red light.

4.- Zolour develop the re-exposed layer.

"5. Wash.

:6. Expose the other layer uniformly to-.green light.

7. Colour develop this last re-exposed layer.

.8. Wash.

b'. Remove all. silver.

-INTERNAL LATENT' IMAGE FORMING TYPE A red selsitised emulsion .of this type coated over:a green sensitised emulsion of the same type.

After:exposure the processing can be: 1. While immersed in one "surface" colour developer exposed uniformly to red light and allow the red record layer to develop.

-2. Wash.

:3. While immersed in another "surface" colour developer expose uniformly to green light through the back:and allow the green record layer to develop.

4. Wash.

5. Remove all silver.

6. Wash.

'Thus, when such emulsions are employed for example as mixed emulsions or superimposed emulsion layers in colour photography, the method of the present invention enables coloured positives to be obtained more expeditiously on a material containing a negative latent image of a coloured object 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 as less than one tenth of the blue sensitivity of the blue-sensitive emulsion (see British Patent No. 540,444); the following procedure may be adopted to process such an exposed material.

First immerse the material in a "surface" colourforming developer containing a colour coupler giving a blue-green image and then: expose the material to a uniform red light; the negative latent image in the lowest red sensitive layer will then develop as a blue-green coloured positive.

After washing, immerse the material in a eolour-forming surface developer containing a Colour coupler giving a magenta image anh then expose the material to a green light; the negative latent image in the green sensitive emulsion 'Will then develop as a magenta-coloured 'positive.

Finally, immerse the material in a coloiurforming Surface developer containing a colour coupler giving a yellow image and then expose the material to ;blue light; the negative latent image in the -blue sensitive layer 'will then -develop as 'a yellow eblOUtred positive. Colour forming 'deVelUpers 'given "Such :blue-green :miagenta :anid yellow images (respectively) suitable for this purpose are those of the kind commonly embloyed inicolou8r photography which have; little or,.no t~nide~!eyto : di'solve~Tilver halide such as 'those in British:PatentitNo. 507,841.

The;saccompanying drawings show 'a flow-diagram whieh:depicts graphically the application of g our invention 'to' a three-colour :material -as described"above. In the first sheet of drawings, at B is shdWn a three colour Sensitive material conmprising coated on a 'support three superimposed silver '.halide em:llsion layers which are red, green O d and blue sensitive reading from the support. The blue 'sensitivity: 'of the -red and green .sensitive 1ae6rs is very low cimpared to the blue sensitivity of the "bluersensitive layer, viz. less than J the blue ensitiiluesitiitlue sensitive layer. UpOi 1 ebxposure .ofthf e three-colour 'sensitive material shown at B tb:the liýht:.oloured object shown at A,'-a'H~gir tive lateint image of the red part of the col-iured objecttisiformied mostly :inside the silver halide grainS of the red sensitive layer; a negative a latent image :of the green part of the coloured objoet is formfied miostly inside the silver halide grains of:the green sensitive layer ;:and a negative latent :im-age of 'the blue part of the coloured 'Object 'is formed 'mostly inside the silver halide 2- grains6f t:he blue sensitive layer, as shown at C.

Upon 'treatmtet of this exposed three-colour material to "render tt :capable of forming surface latent image 'by imminersing it in a "surface" :colou~r-formini devlbjer containing va colour -80 couplet giving"a blue-green image, the red sensitive layer still tcontains the aforesaid negative latent image mostly inside the silver halide grains, but is now capable of forming surface latent image as SthoWn att ;D. 'Upon exposing the material to a:ti'nform red- ight,;:hreversed (or positive) latent ifage is formed mostly on the surface of the silver halide grains as shown at E. Upon development bf the red-se·nsitive emulsion layer in the aforesaid "surface" colour-forming developer contaifing ýa `cblodur coupler giving a blue-green imnage, a blue-green coloured positive develops in the red-sensitive layer as shown at F. After washing the 'material and upon immersing the Washed 'nmaterIal in a "surface" colour-forming developer 'Containing a colour coupler giving a magenta image, the green sensitive layer still cohtaih's the Ifobesaid negative latent image mostly inside the silver halide grains, but is now bGpable of 'forming surface latent image as shown at G (second sheet of drawings). Upon exposing the material' to uniform green light, a reversed (or ~positive) latent image is formed mostly on the silver halide grains as shown at H. Upon development of the green-sensitive layer in the aforesaid "'surface" colour-forming developer containing a colour coupler giving a magenta imiage, -a magenta 'coloured positive develops in the green-sensitive layer as shown at I. Upon immersing the material in a "surface" colourforming developer Containing a colour coupler giving 'a yellow image, the blue-sensitive layer still contains the aforesaid negative latent image mostly inside the silver halide grains, but is now capable of formiig surface latent image as shown at J. Upon exposing the material to uniform blue light, a reversed (or positive) latent image is formed mostly on 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 yellow image, a yellow coloured positive 'develops in the blue-sensitive layer as shown at L, and a positive record of the coloured object is bomplete.

An alt-rnative-method of processing suith 'a three-colour material is illustrated by considering the case where the layers are in the 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 leversed 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 which 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. g. 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 layer; then develop such silver ferrocyanide with a magenta forming colour developer. The top layer is then 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.

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 200 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.

This application 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 nhited 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 trans1n 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): Hydroquinone ----------------grams-. 5 iN-methyl-p-aminophenol sulphate--do..-Sodium sulphite, anhydrous -------do-. Potassium bromide--------------.do Sodium hydroxide ---. ----------.do-. Sodium thiosulphate, crystals--- do---20 Water to---------_------- ---- ccs 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 25 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 4 minutes at 20° C. in the following developer (I): p-Hydroxyphenylglycine ---------grams-. 10 30 Sodium carbonate, crystals-------- do--- 100 Water to--------------- ----- ccs. 1000 the measurements of density being made at the same points on the logloE 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): 40 Hydroquinone --- ---------gramsN-methyl-p-aminophenol sulphate--do -Sodium sulphite, crystals--------- do--. Potassium bromide--------.--... --.do . Sodium carbonate, crystals---------do-45 Water to--__.---------------------_ ccs uniformly exposing to light the so-treated emulsion to produce latent image some of which is developable by the aforesaid developer (III), de50 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 55 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 III 60 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 65 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 photo70 graphic 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 75 of any one of which emulsions coated on a trans11. 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 200 C. in the following developer (Ila) : Hyidrquinone ------------- - grams- 15 6 N-i;nthyl-p-aminophenol sulphate-- o- - 15 Sodiilfi sulphite, anhydrous------- do-- 50 Potasium bromide___------- do -Sodium hydroxide---------------do-- 25 Sodium thibsulphate, crystals----. do-- 20 10 Wateri to----------------------- ccs_ 1000 gives a transmitted density at any point along the logloE axis, over a range of 3.0 starting from the th'eshold of thee characteristic curve beginning at a density of 0.1 above f6g, at least 10 times the transmitted deinsity obtaiied when an identical test layer ofT the emulsion is developed for 4 miflutes-at 20 C. in the following developer (I): 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, 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 (II) : Hydroquinone .--..------- ---- grams-_ 12 N-methyl-p-aminophenol sulphate--do--- 3 Sodiufi sulphite, crystals--------- do-- 90 Potassium bromide ---..--------- do-- 4 Sodium carbonate, crystals--------do-- 150 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- 4 veloping the uniformly fogged emulsion in-a developer which develops the latent image which is developable-by -developer (III) -andgives 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 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.

3. 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 anyone of which emulsions coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between ;ioo and 1 second and development for 4 minutes at 200 C. in the following developer (Ib): Hydroquinone --------------- grams-. N-methyl-p-aminophenol sulphate- do.--Sodium sulphite, crystals ------ do --Potassium bromide ------------- do --Sodium hydroxide --------- ----. do----Sodium thiosulphate, crystals- ---graims-. 20: Water to.. -------------- --- ccs. 1000: gives a transmitted density at any point alb6n the logloE 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 5-timesthe transmitted density obtained when an identical test layer of the emulsion is developed for 4 iniutes at 200 C. in the following developer (I): p-Hydroxyphenylglycine -. .---- grams-. 10; Sodium carbonate, crystals .------. do.--.. 100 Water to ----------------- ecs-_ 1000; the measurements of density being made at the. same points on the logilE axis, then itthdut developing up the latent images so formed in said emulsions to visible images, treatinganI exposed emulsion to render it capable of:forming latent image developable by the aforesaid 'developer (I), uniformly exposing to light the sotreated emulsion to form latent image soime 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 (I), and developing the second 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 in said second emulsion.

4. The method of producing reversed photographic images comprising exposing to a lighted object or image a photographic material compris-, 'ing 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 'Ao 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 hydroxide ---------------do.-- 150. Sodium thiosulphate, crystals.---- do-- 20 Water to ------------------------ ccs 1000 gives a transmitted density at any point along the. logloE axis, over a range of 3;0 starting from the: threshold of the characteristic curve begirnning 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 200 C. in the following developer (I): 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 logloE axis, then withouit developing up the latent images so formed in said emulsions to visible images, treating-'an expose64 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 (I), and developing the second 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 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 Moo 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 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 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 200 C. in the following developer (III) : Hydroquinone --- ---------- grams-_ N-methyl-p-aminophenol sulphate-do --. Sodium sulphite, crystals ---------do --Potassium bromide .--------..do -Sodium carbonate, crystals --.----. do-Water to ------- --------__-----_ ccs-the measurements of density being made at the same points on the logloE 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__ 10 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 (I), developing the uniformly fogged emulsion in a developer which develops the latent image which is developable by the aforesaid developer (I) and Hydroquinone ------------- grams30. N-methyl-p-aminophenol sulphate-do.--. Sodium sulphite, anhydrous ------do-Potassium bromide -------------.do-.. Sodium hydroxide --------------do-Sodium thiosulphate, crystals .--do--. 35 Water to -------------------- ccs__ gives a transmitted density at any point along the logloE axis, over a range of 3.0 starting from the threshold of the characteristic curve begin40 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): 45 Hydroquinone --------------- grams-_ N-methyl-p-aminophenol sulphate-do.--.

Sodium sulphite, crystals --- do -Potassium bromide ---------- do --_ Sodium carbonate, crystals _-------do-.. 50 Water to ------------------- ccs 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 55 exposed emulsions, treating an exposed emulsion to render it capable of forming latent image developable by the following developer (I): p-Hydroxyphenylglycine ------ grams-. 10 Sodium carbonate, crystals _------. do_.-- 100 60 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 (I), devel65 oping 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 70 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 devel75 oper (I) to produce latent image some of whiche gives no more than a negligible developmnent 6of 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 (I), and developing 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 0oo and 1 second and development for 3 minutes at 200 C. in the following developer (IIa): i:developable by the: foressai&deyeloper (I), and, developing the second uniformly exposed emulsion inr a developer which :develops the latent image which is fdevelopable by the aforesaid developer (I) and gives no more than a negligiblel development of the negative:latent.image formed by.the original exposure compared with the.positive- image which is: developed. in. said second emulsion.

7.. The. method of producing reversed' photo~. graphic images comprising 'exposing ,to a lightedobject or.image a photographic:-materinl comprising isaeparably combined .and''extending over the; same 'area on a.single :support a:.plurality of -photographic silver halide emulsions:a testi layer- of any. one of which emulsions:coated .onas transparent glass support upon exposure to-a.lAtight intensity scale for a.. fixed time ýbetween 'iooth and 1 - second and development for -4 minutes :at; C:. in the following-developer. (1Cb): Hydroquinone ---------- ----grams N-methyl-Op-amincphenol .sulphate -do ---Sodium sulphite, crystals----------do--__ Potassium bromide -------_-- do-Sodium lcarbonate, crystals _. ------ d--. Sodium thiosulphate, crystals ----do--.

Water to ----------------------ccs gives a transmitted density at any point along. the logioE axis, overa- 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 4 minutes at 200 -C. in the following-developer (III) ': Hydroquinone ------- grams.- 12 N-methyl''p-aminophenol sulphate -do.--. 3 Sodium sulphite, crystals ---------- do . '90 Pdtassium bromide ------------ - 4 Sodium carbonate, crystals --------do- - :20 Water to ----------------------ccs 00 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 emuilsions, treat-ing an -exposed emunlsion to render it capable of "forminfg lateft image developable 'by the-following developer f(l : p-Hydroxyphenylglycine. ----grams-- 10 Sodium carbonate, crystals --------do--. 100 Water to ------------------- ccs 1000 uniformly exposing to light the so-treated emulsicn tof:orm 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 devedlopable 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 capableof forming latent image;'developable by -the :aforesaid developer (I) to produce latent image some'of which lis developable by the aforesaid developer (TD, ,-aid.'developing .the second uniformly -exposed emuilsion'in a developer'which develops .the latent image'which is:developable by the aforesaid developer 01b) and gives :no :more: than. -a negligible development 'of the'negative-latent image formed -by the.original exposure compared with'the positive image whishis develbped in said second emulsion.

8. The method of producing: reversed :photogiaphic images: comprising -exposing to:a lightedob ject ior I,7age:a:photographicmaterif comprising inseparably combined and extending :over;-he sam,'e area on.: a-single support a;.plurality of:phlotographic silver halide emulsions.aý' test layer of: 5- any oone-:of which emulsions .coated on a. transparent glass 'support upon: exposureT to a light: inte.nsity:scale or: aixed time between looth and' l1secondc;and jdevelopment for:4 minutesat 20" C.. in:. the. fll:olwing developer (ITh : i' Hydrquinone ------------- grams- 12' N-meithyl-p-aminophenol sulphate. _do..-- 3.

Sodium sulphite, crystals---------- do--- 90 Potassium bromide ----------- do-- 4 Sodium carbonate, crystals -------- do--- 150 15' Sodium thiosulphate, crystals -----do-.. 20: Water to ----.c--------------- - I'00' gives- a- transmitted density:,at any point along the, logiooE .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 10- times, thetransmitted density.-obtained when an:identical; test layer of the emulsion is developed for .4-minutes at 200 C. in the-following developer (III-).: 25' Hydroquinone ------------- grams. N-methyl'-p-aminophenol sulphate -do-Sodium suiphite, -crystals ---------- deo Potassium bromide.------ ---.--_ do_-Sodium carbonate,, crystals --------do---30. Water to --------------- ------ccs_ 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. 3:to render it capable of forming latent.image developable by the following developer (I): p-HydroxyphenylJlycine .-.-- grams.. 10, Sodium carbonate, crystals.-.._-do--- 100f 40 Waterto --------------- ccs.. 1000 uniformly exposing .tolight theeso-tre-ted emiltsion toform.~latent-image 'somentf 'whlich is -deveTopa'ble by-the- aforesaid.developer- C-,developing the uniformly fogged emulsion .in -a. developer. 45:' which develops the.latent'image which is-developable by'the aforesaid. developer (I). and gives no, more. 'han a :negligib:le development of. the ~negative latenritimage formed:by the original.exposure compared:with the positive image whidh.is..devel50 oped, then untiforrmly exposing -to light-another of, said exposed enuilsions which 'has also been treated to render it capable of forming latent image deveropalble .by-the af-oresaid developer ('I) to producezdatentAmage some of -which ,is develop-55 able by-the:'aforesaid devoeloper (Iý, and ldevelbping the. second .uniformly -exposed -emulsion nn 'a developer which developsithe-:latent:image which is:developable by the.aforesaid -developer :(0Iand gives no more than a .negligible development of 60; the.negative latent image formed -by the joriginal exposure 'compared withthe positive-image which is developed in said second emulsion..

EDWARD. BOWES KNOTT.

GUY WILLIAM WILLIS STEVENS.

:-REFERENCES-,Oe ED The 'following references are of record in thefile of this patent: 70-ED STA UViTED 'STATES-:"PATENTS Number 1,996,928 Name' Date Ma'nnes iet-al.... -- - Apr. 9, 1935 76M: . (0Bt'erifleaeaindH lja ifape OTHER REFERENCES Mees, "The Theory of the Photographic Process," published by the Macmillan Co., New York, 1942, pages 150-152, 166-171, 196, 294-297 and 301. 5 (Copy in Div. 67.) Bullock, "Chemical Reactions of The Photographic Latent Image," vol. I; published by Eastman Kodak Co., Rochester, New York, 1927; pages 15, 20, 22, 28, 30, 31, 47, 48, 50, 52, 72, 73, 80-85. (Copy in Div. 67.) Wall, "Photographic Emulsions," published by American Phot. Publ. Co., Boston, 1929; pages 52, 53 and 135-137. (Copy in Div. 67.) 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" read expose; line 72, for "given" read giving; column 11, line 18, for "20 C." read 200 C.; 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, Asistant Commissioer of Patents.