Photographic ligand for inducing disproportionation of silver +1 and processes of use thereof
United States Patent 3893855
Speed increase is obtained in photosensitive silver halide emulsions by disproportionation of Ag+1 associated with the latent image.
US Patent References:
Novel photographic products and processes
Land - December 1968 - 3415644
/3552968.html
Willems et al. - January 1971 - 3552968
ADDITIVE DIFFUSION TRANSFER COLOR PHOTOGRAPHIC PROCESSES AND FILM UNITS FOR USE THEREWITH
Weed - October 1971 - 3615428
Novel photographic products and processes
Land - December 1968 - 3415644
/3552968.html
Willems et al. - January 1971 - 3552968
ADDITIVE DIFFUSION TRANSFER COLOR PHOTOGRAPHIC PROCESSES AND FILM UNITS FOR USE THEREWITH
Weed - October 1971 - 3615428
Application Number:
05/475778
Publication Date:
07/08/1975
Filing Date:
06/03/1974
View Patent Images:
Export Citation:
Assignee:
Polaroid Corporation (Cambridge, MA)
Primary Class:
Other Classes:
430/239, 430/230, 430/600
International Classes:
G03C1/10; G03C1/34; G03C8/06; G03C8/02; G03C7/00; G03C5/54; G03C1/48
Field of Search:
96/29D,29R,76C,76R,77,94R,95,3,65
Primary Examiner:
Klein, David
Attorney, Agent or Firm:
Kiely, Philip G.
Parent Case Data:
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No. 327,797 filed Jan. 29, 1973 now abandoned.
Claims:
What is claimed is
1. A photosensitive silver halide emulsion comprising a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC10##
2. A product as defined in claim 1 wherein the emulsion includes spectral sensitizing agents.
3. A product as defined in claim 1 wherein said emulsion includes chemical sensitizing agents.
4. A product as defined in claim 1 wherein said emulsion contains an antifoggant.
5. A product as defined in claim 1 wherein said ligand is: ##SPC11##
6. A product as defined in claim 1 wherein said ligand is: ##SPC12##
7. ,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (teta)
8. A product as defined in claim 1 wherein said ligand is: ##SPC13##
9. A product as defined in claim 1 wherein said ligand is: ##SPC14##
10. A product as defined in claim 1 wherein said silver halide emulsion is carried on a support.
11. A photographic silver diffusion transfer film unit which comprises photosensitive silver halide, silver precipitating nuclei and associated with said silver halide, a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC15##
12. A product as defined in claim 10 wherein said film unit includes a common support carrying a layer comprising silver precipitating nuclei and a layer comprising silver halide crystals.
13. A product as defined in claim 11 wherein said film unit is a permanent laminate.
14. A product as defined in claim 11 wherein said common support is transparent.
15. A photographic silver diffusion transfer film unit as defined in claim 13 which includes an additive color screen intermediate said transparent common support and next adjacent essential layer.
16. A photographic silver diffusion transfer film unit which comprises a plurality of layers including a photosensitive layer containing photosensitive silver halide and at least one substantially photoinsensitive layer, at least one photoinsensitive layer containing a silver precipitating agent and at least one photoinsensitive layer including a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC16##
17. A product as defined in claim 15 wherein said photosensitive layer containing said silver halide and said photoinsensitive layer containing said silver precipitating agent are carried on separate supports.
18. A product as defined in claim 10 which includes an additive color screen.
19. In a photosensitive element including at least one light-sensitive silver halide layer wherein each of which has a dye image-providing material associated therewith, the improvement which comprises including in at least one silver halide layer a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC17##
20. An element as defined in claim 18 which includes a red-sensitive gelatino silver halide emulsion having a cyan dye image-providing material associated therewith; a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith; and a blue-sensitive gelatino silver halide emulsion having a yellow dye image-providing material associated therewith.
21. An element as defined in claim 18 which includes a positive component including at least a dyeable stratum.
22. A photographic film unit which comprises, in combination:
23. The product as defined in claim 21 wherein said non-aromatic macrocyclic ligand is disposed in each of said silver halide emulsion layers.
24. The product as defined in claim 21 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said image-receiving elements.
25. The product as defined in claim 23 wherein said image-receiving element support layer is transparent.
26. The product as defined in claim 22 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.
27. A photographic process which comprises developing an exposed photosensitive element comprising an exposed silver halide emulsion containing a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC19##
28. A silver diffusion transfer photographic process which comprises, in combination, the steps of:
29. A silver diffusion transfer photographic process which comprises, in combination, the steps of:
30. A diffusion transfer color photographic process as defined in claim 27 wherein said film unit includes a color screen and exposure of said film unit is accomplished by radiation transmitted through said screen.
31. A diffusion transfer multicolor photographic process as defined in claim 29 wherein said color screen comprises a trichromatic additive color screen comprising red, green and blue optical filter elements in a screen pattern.
32. A process which comprises exposing a photosensitive silver halide emulsion, contacting said exposed emulsion with a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC22##
1. A photosensitive silver halide emulsion comprising a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC10##
2. A product as defined in claim 1 wherein the emulsion includes spectral sensitizing agents.
3. A product as defined in claim 1 wherein said emulsion includes chemical sensitizing agents.
4. A product as defined in claim 1 wherein said emulsion contains an antifoggant.
5. A product as defined in claim 1 wherein said ligand is: ##SPC11##
6. A product as defined in claim 1 wherein said ligand is: ##SPC12##
7. ,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane (teta)
8. A product as defined in claim 1 wherein said ligand is: ##SPC13##
9. A product as defined in claim 1 wherein said ligand is: ##SPC14##
10. A product as defined in claim 1 wherein said silver halide emulsion is carried on a support.
11. A photographic silver diffusion transfer film unit which comprises photosensitive silver halide, silver precipitating nuclei and associated with said silver halide, a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC15##
12. A product as defined in claim 10 wherein said film unit includes a common support carrying a layer comprising silver precipitating nuclei and a layer comprising silver halide crystals.
13. A product as defined in claim 11 wherein said film unit is a permanent laminate.
14. A product as defined in claim 11 wherein said common support is transparent.
15. A photographic silver diffusion transfer film unit as defined in claim 13 which includes an additive color screen intermediate said transparent common support and next adjacent essential layer.
16. A photographic silver diffusion transfer film unit which comprises a plurality of layers including a photosensitive layer containing photosensitive silver halide and at least one substantially photoinsensitive layer, at least one photoinsensitive layer containing a silver precipitating agent and at least one photoinsensitive layer including a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC16##
17. A product as defined in claim 15 wherein said photosensitive layer containing said silver halide and said photoinsensitive layer containing said silver precipitating agent are carried on separate supports.
18. A product as defined in claim 10 which includes an additive color screen.
19. In a photosensitive element including at least one light-sensitive silver halide layer wherein each of which has a dye image-providing material associated therewith, the improvement which comprises including in at least one silver halide layer a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC17##
20. An element as defined in claim 18 which includes a red-sensitive gelatino silver halide emulsion having a cyan dye image-providing material associated therewith; a green-sensitive gelatino silver halide emulsion having a magenta dye image-providing material associated therewith; and a blue-sensitive gelatino silver halide emulsion having a yellow dye image-providing material associated therewith.
21. An element as defined in claim 18 which includes a positive component including at least a dyeable stratum.
22. A photographic film unit which comprises, in combination:
23. The product as defined in claim 21 wherein said non-aromatic macrocyclic ligand is disposed in each of said silver halide emulsion layers.
24. The product as defined in claim 21 including a rupturable container retaining an aqueous alkaline processing composition affixed one edge of said photosensitive and said image-receiving elements and adapted upon rupture to distribute its contents intermediate said superposed photosensitive and said image-receiving elements.
25. The product as defined in claim 23 wherein said image-receiving element support layer is transparent.
26. The product as defined in claim 22 wherein said photographic film unit comprises a composite structure comprising said photosensitive element and said image-receiving element permanently affixed each to the other in superposed relationship, the support layers of each of said elements comprising the extremities of said composite structure.
27. A photographic process which comprises developing an exposed photosensitive element comprising an exposed silver halide emulsion containing a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC19##
28. A silver diffusion transfer photographic process which comprises, in combination, the steps of:
29. A silver diffusion transfer photographic process which comprises, in combination, the steps of:
30. A diffusion transfer color photographic process as defined in claim 27 wherein said film unit includes a color screen and exposure of said film unit is accomplished by radiation transmitted through said screen.
31. A diffusion transfer multicolor photographic process as defined in claim 29 wherein said color screen comprises a trichromatic additive color screen comprising red, green and blue optical filter elements in a screen pattern.
32. A process which comprises exposing a photosensitive silver halide emulsion, contacting said exposed emulsion with a non-aromatic macrocyclic ligand having four electron donor atoms of the formula: ##SPC22##
Description:
BACKGROUND OF THE INVENTION
In the Oct. 4, 1972 issue of the Journal of the American Chemical Society, page 7189-7190, there is reported ligand-induced disproportionation of silver + 1 . The article reports that contrary to a disproportionation of copper and gold wherein the relatively high heat of hydration favors the disproportionation of the copper + 1 or gold + 1 ions, the relatively low heat of hydration of Ag + 2 disfavors such a reaction, i.e., Ag + 2 is highly unstable. However, by employing a macrocyclic ligand which is relatively large and flat, the reaction of Ag + 1 and the ligand provides relatively high yields of Ag + 2 L and Ag 0 wherein L is the ligand and the Ag 0 is deposited as a mirror. The reaction may be carried out in water or methanol in which Ag + 1 is soluble.
The stability of the complex is believed to be the result of the coordination of the Ag + 2 ion by the tetra-nitrogen macrocyclic ligand in an approximately square planar geometry. Thus, the stability of the high oxidation state of silver is believed to be the consequence of the four donor nitrogens being tightly bound to Ag + 2 in an approximately square planar geometry.
A novel photographic system has now been found employing the above-described disproportionation reaction.
SUMMARY OF THE INVENTION
Speed enhancement is achieved in photosensitive silver halide emulsions by the disproportionation of Ag + 1 in the vicinity of the latent image. Such disproportionation is preferably carried out by contacting the latent image with a macrocyclic ligand prior to development. Preferably, the ligand is disposed in the emulsion prior to exposure.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a photosensitive element which includes a macrocyclic ligand capable of inducing disproportionation in Ag + 1 . By associating such a ligand with the exposed photosensitive silver halide emulsion layer, enhanced speed is achieved. In addition, substantially no fog is found in the photosensitive elements of the present invention.
The ligand is either disposed in the silver halide emulsion prior to exposure or is applied to the exposed emulsion prior to development. Thus, the action of the ligand on the latent image occurs before development.
A silver halide crystal consists of positively charged silver ion (Ag + 1 ) and negatively charged halide ions. A photon absorbed onto the crystal provides an electron which combines with an Ag + 1 ion and reduces it to a neutral silver atom (Ag 0 ). As this process proceeds with a given quantity of photons absorbed, a small stable cluster of reduced silver atoms (latent image specks) are formed. These latent image specks serve as catalytic centers for the reduction to silver of silver ions in the exposed crystals by the action of the photographic developer. This reduced mass of silver forms the image. The speed of a photographic system relates to the number of photons incident on a crystal to provide the latent image specks capable of development. The fewer the photons required to produce Ag 0 , the greater the speed.
While not intending to be bound by theory, it is believed that by contacting the silver halide emulsion with the above-described ligand, the size of the latent image formed by exposure of the emulsion is increased, i.e., the speed is increased. Thus, the Ag + 1 ions in the vicinity of and on the crystal which are believed to be associated with the formation of the latent image are reacted with the ligand and then disproportionated to provide Ag 0 , which enlarges the latent image, and an Ag + 2 complex. The following general equation illustrates the described reaction:
2Ag + 1 + L Hs O AgL + 2 + Ag 0
Thus, the presence of a macrocyclic ligand in the emulsion acts to rapidly produce Ag 0 in the latent image upon exposure to a degree sufficient to build up the size of the latent image to produce a speed increase. The described macrocyclic ligand can be characterized as a sensitizer or latensification agent.
The ligand employed in the present invention is a non-aromatic macrocyclic ligand, i.e., long and flat, capable of stabilizing the Ag + 2 ion and which possesses four electron donor atoms, preferably containing four atoms capable of providing the described stabilizing effect to silver. Thus, the ligands suitable for use in the present invention may be represented by the formula: ##SPC1##
wherein each X is a carbon chain of at least two carbon atoms.
Preferably, the ligand is a saturated or unsaturated macrocyclic Schiff base amine.
As examples of suitable ligands, mention may be made of the following: ##SPC2## ##SPC3##
5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradec ane (teta) ##SPC4##
5,5,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec ane (tet b)
The preparation of such ligands is known to the art. See, for example, J.A.C.S. 2644 (1964).
The following non-limiting examples illustrate the novel emulsions of the present invention.
EXAMPLE I
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of magenta dye developer of the formula: ##SPC5##
in about 150 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g silver of Compound B at a coverage of about 85 mgs./ft. 2 of silver and about 85 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 containing about 8 mgs./ft. 2 of 4'-methylphenylhydroquinone. The thus-formed negative was exposed through a step wedge to selectively filtered radiation and then processed by contacting the negative with a processing composition while in superposition with an image-receiving element in the dark for 10 minutes. The image-receiving element comprised a 4 mil polyethylene terephthalate film base having coated thereon the following layers:
1. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of 85% phosphoric acid to provide a polymeric acid layer approximately 0.75 mil thick;
2. a 10% aqueous emulsion of a diacetone acrylamide/acrylamide copolymer grafted onto a polyvinyl alcohol backbone to provide an inert spacer layer approximately 0.3 mil thick; and
3. A 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of approximately 600 mgs./ft. 2 , to provide a polymeric image-receiving layer approximately 0.40 mil thick. The processing composition comprised the following:
Water 100 cc. Potassium hydroxide 7.5 g. Cesium hydroxide 4.7 g. Titanium dioxide 50 g. Carboxymethyl cellulose sodium salt 3.5 g. Benzotriazole 1.0 g. 5-bromo-6-methyl-4- azabenzimidazole 0.1 g. 2-methylimidazole 0.35 g. N-phenethyl-α-picolinium bromide 1.75 g.
The film unit of the present invention, compared with a film unit prepared and processed as above except that no macrocyclic ligand was disposed therein, showed a speed enhancement of about one step.
The silver halide emulsions of the present invention are suitable for employment in both color and black and white photographic systems.
The present invention is particularly useful in black and white silver transfer processes.
Diffusion transfer processes are now quite well known and their details need not be repeated here. In a silver transfer process, for example, a photoexposed silver halide material and a silver precipitating material are subjected to an aqueous alkaline solution comprising at least a silver halide developing agent and a silver halide solvent. The developing agent reduces exposed silver halide to silver and the solvent reacts with unreduced silver halide to form a complex silver salt that migrates to the silver precipitating material where it is precipitated or reduced to form a visible silver image.
At the completion of the process the two strata may be separated in order to render the positive print visible. Alternatively, in accordance with the teachings of U.S. Pat. No. 2,861,885, the two strata need not be separated in order to render the positive print visible.
EXAMPLE II
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of yellow dye developer of the formula: ##SPC6##
in about 75 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g. silver of Compound B at a coverage of about 85 mgs./ft. 2 of silver and about 85 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 containing about 8 mgs./ft. 2 of 4'-methylphenylhydroquinone. The thus-formed negative was exposed and processed as in Example I. The image-receiving element employed was the same as that used in Example I. The processing composition comprised:
Water 100 cc. Potassium hydroxide 10.6 g. Lithium hydroxide monohydride 0.45 g. Titanium dioxide 95.8 g. Carboxymethyl cellulose sodium salt 1.84 g. Benzotriazole 1.27 g. 5-bromo-6-methyl-4- azabenzimidazole .064 g. N-phenethyl-α-picolinium bromide 1.65 g. 6-methyl uracil 0.67 g. Lithium nitrate 0.22 g. N-2-hydroxyethyl-N,N',N'-triscar- boxmethyl diamine tetra- acetic acid 1.9 g. Bis(-aminoethyl)-sulfide 0.05 g. Carbowax (Polyethylene glycol, -M.W. - 6000) 1.23 g. Silica SiO 2 1.67 g. N-benzyl-α-picolinium bromide 2.86 g. 6-benzylaminopurine 0.62 g. ##SPC7##
EXAMPLE III
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of cyan dye developer of the formula: ##SPC8##
in about 75 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g silver of Compound B at a coverage of about 150 mgs./ft. 2 of silver and about 150 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 . The thus-formed negative was exposed and processed as in Example I above. The image-receiving element employed was the same as that employed in Example I. The processing composition comprised:
Water 100 cc. Potassium hydroxide 10.5 g. Lithium hydroxide monohydride 0.45 g. Titanium dioxide 95.8 g. Carboxymethyl cellulose sodium salt 2.31 g Benzotriazole 1.27 5-bromo-6-methyl-4- azabenzimidazole .064 N-phenethyl-α-picolinium bromide 1.65 6-methyl uracil 0.67 Lithium nitrate 0.22 N-2-hydroxyethyl-N,N', N'-triscar- boxmethyl diamine tetraacetic acid 1.9 Bis(-aminoethyl)-sulfide 0.05 Carbowax (Polyethylene glycol, M.W. 6000) Silica 1.67 N-benzyl-α-picolinium bromide 2.86 6-benzylaminopurine 0.62 ##SPC9##
EXAMPLE IV
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of hydroquinone in 50 mgs./ft. 2 of gelatin. Over the described layer was coated a blue-sensitive silver iodobromide emulsion containing 4 mg./g of silver of Compound B, at a coverage of about 150 mgs./ft. 2 of silver and 150 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 and a layer of succinaldehyde at a coverage of about 11.5 mgs./ft. 2 . The thus-formed negative was exposed through a step wedge to selectively filtered radiation and then processed by contacting the negative for six minutes in the dark with a processing composition while in superposition with a polyester cover sheet. The processing composition comprised the following:
Water 100 cc. Potassium hydroxide 7.5 g. Cesium hydroxide 4.7 g. Titanium dioxide 50 g. Carboxymethyl cellulose 3.5 g. Benzotriazole 1.0 g. 5-bromo-6-methyl-4- azabenzimidazole 0.1 g. 2-methylimidazole 0.35 g. N-phenethyl-α-picolinium bromide 1.75 g.
At the end of that time, the development was stopped by washing the negative with acetic acid. Compared to a control film unit prepared and processed in the same manner except that the control did not contain Compound B, the film unit of this invention showed about one stop increase in speed.
EXAMPLE V
The procedure of Example I was repeated except that the emulsion contained no ligand and the exposed emulsion was contacted with a methanol solution of the ligand prior to exposure. Approximately one stop speed increase was noted over a control as well as a lower D min .
Employing silver halide emulsion of the present invention will provide enhanced speed in such systems by providing a greater quantity of reduced silver per photon of exposure than would be obtained in an emulsion which was not contacted with the macrocyclic ligand.
Additive color photography involves the exposure of a photosensitive silver halide stratum through an optical screen element or reseau which possesses filter or screen elements selectively transmitting predetermined portions of the electromagnetic radiation incident on said screen. Processing of the thus-exposed silver halide stratum results in the deposit of silver as a function of the degree of exposure behind specific segments of the filter elements to modulate the quantity of light passing through the given screen elements during projection of the thus-recorded image.
In additive color screen units, the photoresponsive material and the color screen may comprise separate and distinct elements appropriately registered during exposure and during viewing or projection of the image. Thus, subsequent to initial exposure of the photoresponsive material, the screen may be removed to permit processing and formation of the silver image, and then recombined with the thus-formed silver image for viewing of the finished image. It is preferred, however, to permanently position the additive color screen and the photoresponsive material together. In such permanent arrangement, it is, of course, necessary to insulate the screen by, for example, barrier elements or intermediate layers, to protect the screen from degradation or change by the action of the processing composition applied to the photoresponsive material to develop the image recorded therein.
Generally, suitable film assemblages comprise a panchromatically sensitized silver halide stratum and a multicolor additive color screen. As examples of such structures, reference may be had to the Dufay film units and those of Ducos DuHauron. A variety of conventional photosensitive layers may be employed in additive film units depending upon the specific type of processing to be employed. For example, depending upon the specific photosensitive layer selected, a direct negative image and a direct positive image may be formed by reversal techniques, a direct image by the employment of a conventional direct positive emulsion; by silver diffusion transfer processing or by the formation in a separate layer of a separate positive image which is then placed in registration with the same screen used for exposure of the film unit, or with a substantially identical screen.
A preferred film unit employs an image-receiving component intermediate the photosensitive silver halide stratum and the additive multicolor screen. In such a film unit, exposure of the silver halide emulsion is accomplished through the screen unit and the image-receiving component. Subsequent processing results in the formation of a positive silver image in the image-receiving component next adjacent the additive multicolor screen. The aforementioned film unit is one example of a structure which obviates registration problems since the screen employed for exposing is in automatic registration with the positive silver image for viewing. In the aforementioned film unit, the silver halide stratum may be removed or allowed to remain in position subsequent to formation of the positive silver image.
As examples of suitable film structures which comprise negative and positive images in superposition and formed by diffusion transfer reversal processes, mention may be made of U.S. Pat. Nos. 2,861,885; 2,726,154; 2,944,894; 3,536,488; and also U.S. Pat. Nos. 3,615,427; 3,615,428; 3,615,429 and 3,615,426.
The utility of such film units wherein the silver halide layer remains an integral portion of the film unit subsequent to positive image formation is achieved by employing as the image-receiving element a layer which provides an unusually effective silver precipitating environment which causes the silver deposited therein to possess an extraordinarily high covering power in comparison with negative silver developed in the silver halide layer. For greater discussion of such a phenomenon, see Edwin H. Land, One Step Photography, Photographic Journal, Section A, pages 7 to 15, January, 1950.
The above-mentioned integral film unit applications are particularly desirable for employment as cine film for motion picture projection, for example, such as the cine film system described in U.S. Pat. No. 3,615,427 issued Oct. 26, 1971. Processing of such film units, as well as the specific composition of the processing composition, is detailed in the aforementioned patents and applications.
Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.
The dye image-providing materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.
As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.
In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a green- and a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.
A particularly useful system for forming color images by diffusion transfer is that described in U.S. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye image-providing materials. U.S. Pat. No. 2,983,606 is incorporated herein in its entirety.
In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or "negative component" comprising at least a light-sensitive layer, e.g., a gelatino silver halide emulsion layer, having a dye image-providing material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed receiving element or "positive component" comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negative-positive film units wherein the negative and positive components are laminated and/or otherwise physically retained together at least prior to image formation.
While the present invention is applicable both to those systems wherein the dyeable stratum is contained on a separate element and to those systems wherein the dyeable stratum and the photosensitive strata comprise a unitary structure, of particular interest are those integral negative-positive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component need not be separated from the negative component for viewing purposes. As examples of such integral negative-positive film units, mention may be made of those described and claimed in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,573,043; 3,576,625; 3,573,042; 3,594,164 and 3,594,165.
The specific composition or method of preparation of silver halide emulsions suitable for use in the present invention is not critical to the operation of the present invention. For example, emulsions of the present invention may be employed in emulsions for wet processing, emulsions employed in diffusion transfer processing and direct positive emulsions. Conventional spectral and chemical sensitizers may be employed as well as optional additives such as coating aids, hardeners, viscosity increasing agents, stabilizers, preservatives, and the like.
Similarly, the photoresponsive material will preferably comprise a crystal of a silver compound, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide, silver chloroiodobromide, or silver iodobromide, of varying halide ratios and varying silver concentrations.
In the Oct. 4, 1972 issue of the Journal of the American Chemical Society, page 7189-7190, there is reported ligand-induced disproportionation of silver + 1 . The article reports that contrary to a disproportionation of copper and gold wherein the relatively high heat of hydration favors the disproportionation of the copper + 1 or gold + 1 ions, the relatively low heat of hydration of Ag + 2 disfavors such a reaction, i.e., Ag + 2 is highly unstable. However, by employing a macrocyclic ligand which is relatively large and flat, the reaction of Ag + 1 and the ligand provides relatively high yields of Ag + 2 L and Ag 0 wherein L is the ligand and the Ag 0 is deposited as a mirror. The reaction may be carried out in water or methanol in which Ag + 1 is soluble.
The stability of the complex is believed to be the result of the coordination of the Ag + 2 ion by the tetra-nitrogen macrocyclic ligand in an approximately square planar geometry. Thus, the stability of the high oxidation state of silver is believed to be the consequence of the four donor nitrogens being tightly bound to Ag + 2 in an approximately square planar geometry.
A novel photographic system has now been found employing the above-described disproportionation reaction.
SUMMARY OF THE INVENTION
Speed enhancement is achieved in photosensitive silver halide emulsions by the disproportionation of Ag + 1 in the vicinity of the latent image. Such disproportionation is preferably carried out by contacting the latent image with a macrocyclic ligand prior to development. Preferably, the ligand is disposed in the emulsion prior to exposure.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a photosensitive element which includes a macrocyclic ligand capable of inducing disproportionation in Ag + 1 . By associating such a ligand with the exposed photosensitive silver halide emulsion layer, enhanced speed is achieved. In addition, substantially no fog is found in the photosensitive elements of the present invention.
The ligand is either disposed in the silver halide emulsion prior to exposure or is applied to the exposed emulsion prior to development. Thus, the action of the ligand on the latent image occurs before development.
A silver halide crystal consists of positively charged silver ion (Ag + 1 ) and negatively charged halide ions. A photon absorbed onto the crystal provides an electron which combines with an Ag + 1 ion and reduces it to a neutral silver atom (Ag 0 ). As this process proceeds with a given quantity of photons absorbed, a small stable cluster of reduced silver atoms (latent image specks) are formed. These latent image specks serve as catalytic centers for the reduction to silver of silver ions in the exposed crystals by the action of the photographic developer. This reduced mass of silver forms the image. The speed of a photographic system relates to the number of photons incident on a crystal to provide the latent image specks capable of development. The fewer the photons required to produce Ag 0 , the greater the speed.
While not intending to be bound by theory, it is believed that by contacting the silver halide emulsion with the above-described ligand, the size of the latent image formed by exposure of the emulsion is increased, i.e., the speed is increased. Thus, the Ag + 1 ions in the vicinity of and on the crystal which are believed to be associated with the formation of the latent image are reacted with the ligand and then disproportionated to provide Ag 0 , which enlarges the latent image, and an Ag + 2 complex. The following general equation illustrates the described reaction:
2Ag + 1 + L H
Thus, the presence of a macrocyclic ligand in the emulsion acts to rapidly produce Ag 0 in the latent image upon exposure to a degree sufficient to build up the size of the latent image to produce a speed increase. The described macrocyclic ligand can be characterized as a sensitizer or latensification agent.
The ligand employed in the present invention is a non-aromatic macrocyclic ligand, i.e., long and flat, capable of stabilizing the Ag + 2 ion and which possesses four electron donor atoms, preferably containing four atoms capable of providing the described stabilizing effect to silver. Thus, the ligands suitable for use in the present invention may be represented by the formula: ##SPC1##
wherein each X is a carbon chain of at least two carbon atoms.
Preferably, the ligand is a saturated or unsaturated macrocyclic Schiff base amine.
As examples of suitable ligands, mention may be made of the following: ##SPC2## ##SPC3##
5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradec ane (teta) ##SPC4##
5,5,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradec ane (tet b)
The preparation of such ligands is known to the art. See, for example, J.A.C.S. 2644 (1964).
The following non-limiting examples illustrate the novel emulsions of the present invention.
EXAMPLE I
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of magenta dye developer of the formula: ##SPC5##
in about 150 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g silver of Compound B at a coverage of about 85 mgs./ft. 2 of silver and about 85 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 containing about 8 mgs./ft. 2 of 4'-methylphenylhydroquinone. The thus-formed negative was exposed through a step wedge to selectively filtered radiation and then processed by contacting the negative with a processing composition while in superposition with an image-receiving element in the dark for 10 minutes. The image-receiving element comprised a 4 mil polyethylene terephthalate film base having coated thereon the following layers:
1. the partial butyl ester of polyethylene/maleic anhydride copolymer prepared by refluxing, for 14 hours, 300 grams of high viscosity poly-(ethylene/maleic anhydride), 140 grams of n-butyl alcohol and 1 cc. of 85% phosphoric acid to provide a polymeric acid layer approximately 0.75 mil thick;
2. a 10% aqueous emulsion of a diacetone acrylamide/acrylamide copolymer grafted onto a polyvinyl alcohol backbone to provide an inert spacer layer approximately 0.3 mil thick; and
3. A 2:1 mixture, by weight, of polyvinyl alcohol and poly-4-vinylpyridine, at a coverage of approximately 600 mgs./ft. 2 , to provide a polymeric image-receiving layer approximately 0.40 mil thick. The processing composition comprised the following:
Water 100 cc. Potassium hydroxide 7.5 g. Cesium hydroxide 4.7 g. Titanium dioxide 50 g. Carboxymethyl cellulose sodium salt 3.5 g. Benzotriazole 1.0 g. 5-bromo-6-methyl-4- azabenzimidazole 0.1 g. 2-methylimidazole 0.35 g. N-phenethyl-α-picolinium bromide 1.75 g.
The film unit of the present invention, compared with a film unit prepared and processed as above except that no macrocyclic ligand was disposed therein, showed a speed enhancement of about one step.
The silver halide emulsions of the present invention are suitable for employment in both color and black and white photographic systems.
The present invention is particularly useful in black and white silver transfer processes.
Diffusion transfer processes are now quite well known and their details need not be repeated here. In a silver transfer process, for example, a photoexposed silver halide material and a silver precipitating material are subjected to an aqueous alkaline solution comprising at least a silver halide developing agent and a silver halide solvent. The developing agent reduces exposed silver halide to silver and the solvent reacts with unreduced silver halide to form a complex silver salt that migrates to the silver precipitating material where it is precipitated or reduced to form a visible silver image.
At the completion of the process the two strata may be separated in order to render the positive print visible. Alternatively, in accordance with the teachings of U.S. Pat. No. 2,861,885, the two strata need not be separated in order to render the positive print visible.
EXAMPLE II
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of yellow dye developer of the formula: ##SPC6##
in about 75 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g. silver of Compound B at a coverage of about 85 mgs./ft. 2 of silver and about 85 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 containing about 8 mgs./ft. 2 of 4'-methylphenylhydroquinone. The thus-formed negative was exposed and processed as in Example I. The image-receiving element employed was the same as that used in Example I. The processing composition comprised:
Water 100 cc. Potassium hydroxide 10.6 g. Lithium hydroxide monohydride 0.45 g. Titanium dioxide 95.8 g. Carboxymethyl cellulose sodium salt 1.84 g. Benzotriazole 1.27 g. 5-bromo-6-methyl-4- azabenzimidazole .064 g. N-phenethyl-α-picolinium bromide 1.65 g. 6-methyl uracil 0.67 g. Lithium nitrate 0.22 g. N-2-hydroxyethyl-N,N',N'-triscar- boxmethyl diamine tetra- acetic acid 1.9 g. Bis(-aminoethyl)-sulfide 0.05 g. Carbowax (Polyethylene glycol, -M.W. - 6000) 1.23 g. Silica SiO 2 1.67 g. N-benzyl-α-picolinium bromide 2.86 g. 6-benzylaminopurine 0.62 g. ##SPC7##
EXAMPLE III
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of cyan dye developer of the formula: ##SPC8##
in about 75 mgs./ft. 2 of gelatin. Over the above-described layer was coated a blue-sensitized silver iodobromide emulsion containing 4 mg./g silver of Compound B at a coverage of about 150 mgs./ft. 2 of silver and about 150 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 . The thus-formed negative was exposed and processed as in Example I above. The image-receiving element employed was the same as that employed in Example I. The processing composition comprised:
Water 100 cc. Potassium hydroxide 10.5 g. Lithium hydroxide monohydride 0.45 g. Titanium dioxide 95.8 g. Carboxymethyl cellulose sodium salt 2.31 g Benzotriazole 1.27 5-bromo-6-methyl-4- azabenzimidazole .064 N-phenethyl-α-picolinium bromide 1.65 6-methyl uracil 0.67 Lithium nitrate 0.22 N-2-hydroxyethyl-N,N', N'-triscar- boxmethyl diamine tetraacetic acid 1.9 Bis(-aminoethyl)-sulfide 0.05 Carbowax (Polyethylene glycol, M.W. 6000) Silica 1.67 N-benzyl-α-picolinium bromide 2.86 6-benzylaminopurine 0.62 ##SPC9##
EXAMPLE IV
A film unit was prepared by coating a polyester support with 50 mgs./ft. 2 of hydroquinone in 50 mgs./ft. 2 of gelatin. Over the described layer was coated a blue-sensitive silver iodobromide emulsion containing 4 mg./g of silver of Compound B, at a coverage of about 150 mgs./ft. 2 of silver and 150 mgs./ft. 2 of gelatin. Over the emulsion layer was coated a layer of gelatin at a coverage of about 30 mgs./ft. 2 and a layer of succinaldehyde at a coverage of about 11.5 mgs./ft. 2 . The thus-formed negative was exposed through a step wedge to selectively filtered radiation and then processed by contacting the negative for six minutes in the dark with a processing composition while in superposition with a polyester cover sheet. The processing composition comprised the following:
Water 100 cc. Potassium hydroxide 7.5 g. Cesium hydroxide 4.7 g. Titanium dioxide 50 g. Carboxymethyl cellulose 3.5 g. Benzotriazole 1.0 g. 5-bromo-6-methyl-4- azabenzimidazole 0.1 g. 2-methylimidazole 0.35 g. N-phenethyl-α-picolinium bromide 1.75 g.
At the end of that time, the development was stopped by washing the negative with acetic acid. Compared to a control film unit prepared and processed in the same manner except that the control did not contain Compound B, the film unit of this invention showed about one stop increase in speed.
EXAMPLE V
The procedure of Example I was repeated except that the emulsion contained no ligand and the exposed emulsion was contacted with a methanol solution of the ligand prior to exposure. Approximately one stop speed increase was noted over a control as well as a lower D min .
Employing silver halide emulsion of the present invention will provide enhanced speed in such systems by providing a greater quantity of reduced silver per photon of exposure than would be obtained in an emulsion which was not contacted with the macrocyclic ligand.
Additive color photography involves the exposure of a photosensitive silver halide stratum through an optical screen element or reseau which possesses filter or screen elements selectively transmitting predetermined portions of the electromagnetic radiation incident on said screen. Processing of the thus-exposed silver halide stratum results in the deposit of silver as a function of the degree of exposure behind specific segments of the filter elements to modulate the quantity of light passing through the given screen elements during projection of the thus-recorded image.
In additive color screen units, the photoresponsive material and the color screen may comprise separate and distinct elements appropriately registered during exposure and during viewing or projection of the image. Thus, subsequent to initial exposure of the photoresponsive material, the screen may be removed to permit processing and formation of the silver image, and then recombined with the thus-formed silver image for viewing of the finished image. It is preferred, however, to permanently position the additive color screen and the photoresponsive material together. In such permanent arrangement, it is, of course, necessary to insulate the screen by, for example, barrier elements or intermediate layers, to protect the screen from degradation or change by the action of the processing composition applied to the photoresponsive material to develop the image recorded therein.
Generally, suitable film assemblages comprise a panchromatically sensitized silver halide stratum and a multicolor additive color screen. As examples of such structures, reference may be had to the Dufay film units and those of Ducos DuHauron. A variety of conventional photosensitive layers may be employed in additive film units depending upon the specific type of processing to be employed. For example, depending upon the specific photosensitive layer selected, a direct negative image and a direct positive image may be formed by reversal techniques, a direct image by the employment of a conventional direct positive emulsion; by silver diffusion transfer processing or by the formation in a separate layer of a separate positive image which is then placed in registration with the same screen used for exposure of the film unit, or with a substantially identical screen.
A preferred film unit employs an image-receiving component intermediate the photosensitive silver halide stratum and the additive multicolor screen. In such a film unit, exposure of the silver halide emulsion is accomplished through the screen unit and the image-receiving component. Subsequent processing results in the formation of a positive silver image in the image-receiving component next adjacent the additive multicolor screen. The aforementioned film unit is one example of a structure which obviates registration problems since the screen employed for exposing is in automatic registration with the positive silver image for viewing. In the aforementioned film unit, the silver halide stratum may be removed or allowed to remain in position subsequent to formation of the positive silver image.
As examples of suitable film structures which comprise negative and positive images in superposition and formed by diffusion transfer reversal processes, mention may be made of U.S. Pat. Nos. 2,861,885; 2,726,154; 2,944,894; 3,536,488; and also U.S. Pat. Nos. 3,615,427; 3,615,428; 3,615,429 and 3,615,426.
The utility of such film units wherein the silver halide layer remains an integral portion of the film unit subsequent to positive image formation is achieved by employing as the image-receiving element a layer which provides an unusually effective silver precipitating environment which causes the silver deposited therein to possess an extraordinarily high covering power in comparison with negative silver developed in the silver halide layer. For greater discussion of such a phenomenon, see Edwin H. Land, One Step Photography, Photographic Journal, Section A, pages 7 to 15, January, 1950.
The above-mentioned integral film unit applications are particularly desirable for employment as cine film for motion picture projection, for example, such as the cine film system described in U.S. Pat. No. 3,615,427 issued Oct. 26, 1971. Processing of such film units, as well as the specific composition of the processing composition, is detailed in the aforementioned patents and applications.
Various diffusion transfer systems for forming color images have heretofore been disclosed in the art. Generally speaking, such systems rely for color image formation upon a differential in mobility or solubility of a dye image-providing material obtained as a function of development so as to provide an imagewise distribution of such material which is more diffusible and which is therefore selectively transferred, at least in part, by diffusion, to a superposed dyeable stratum to impart thereto the desired color transfer image. The differential in mobility or solubility may for example be obtained by a chemical action such as a redox reaction or a coupling reaction.
The dye image-providing materials which may be employed in such processes generally may be characterized as either (1) initially soluble or diffusible in the processing composition but are selectively rendered non-diffusible in an imagewise pattern as a function of development; or (2) initially insoluble or non-diffusible in the processing composition but which are selectively rendered diffusible in an imagewise pattern as a function of development. These materials may be complete dyes or dye intermediates, e.g., color couplers.
As examples of initially soluble or diffusible materials and their application in color diffusion transfer, mention may be made of those disclosed, for example, in U.S. Pat. Nos. 2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 2,774,668; and 2,983,606. As examples of initially non-diffusible materials and their use in color transfer systems, mention may be made of the materials and systems disclosed in U.S. Pat. Nos. 3,443,939; 3,443,940; 3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294 and 3,445,228.
In any of these systems, multicolor images are obtained by employing a film unit containing at least two selectively sensitized silver halide layers each having associated therewith a dye image-providing material exhibiting desired spectral absorption characteristics. The most commonly employed elements of this type are the so-called tripack structures employing a blue-, a green- and a red-sensitive silver halide layer having associated therewith, respectively, a yellow, a magenta and a cyan dye image-providing material.
A particularly useful system for forming color images by diffusion transfer is that described in U.S. Pat. No. 2,983,606, employing dye developers (dyes which are also silver halide developing agents) as the dye image-providing materials. U.S. Pat. No. 2,983,606 is incorporated herein in its entirety.
In color diffusion transfer systems of the foregoing description, color images are obtained by exposing a photosensitive element or "negative component" comprising at least a light-sensitive layer, e.g., a gelatino silver halide emulsion layer, having a dye image-providing material associated therewith in the same or in an adjacent layer, to form a developable image; developing this exposed element with a processing composition to form an imagewise distribution of a soluble and diffusible image-providing material; and transferring this imagewise distribution, at least in part, by diffusion, to a superposed receiving element or "positive component" comprising at least a dyeable stratum to impart to this stratum a color transfer image. The negative and positive components may be separate elements which are brought together during processing and thereafter either retained together as the final print or separated following image formation; or they may together comprise a unitary structure, e.g., integral negative-positive film units wherein the negative and positive components are laminated and/or otherwise physically retained together at least prior to image formation.
While the present invention is applicable both to those systems wherein the dyeable stratum is contained on a separate element and to those systems wherein the dyeable stratum and the photosensitive strata comprise a unitary structure, of particular interest are those integral negative-positive film units adapted for forming color transfer images viewable without separation, i.e., wherein the positive component need not be separated from the negative component for viewing purposes. As examples of such integral negative-positive film units, mention may be made of those described and claimed in U.S. Pat. Nos. 3,415,644; 3,415,645; 3,415,646; 3,473,925; 3,573,043; 3,576,625; 3,573,042; 3,594,164 and 3,594,165.
The specific composition or method of preparation of silver halide emulsions suitable for use in the present invention is not critical to the operation of the present invention. For example, emulsions of the present invention may be employed in emulsions for wet processing, emulsions employed in diffusion transfer processing and direct positive emulsions. Conventional spectral and chemical sensitizers may be employed as well as optional additives such as coating aids, hardeners, viscosity increasing agents, stabilizers, preservatives, and the like.
Similarly, the photoresponsive material will preferably comprise a crystal of a silver compound, for example, one or more of the silver halides such as silver chloride, silver iodide, silver bromide, or mixed silver halides such as silver chlorobromide, silver chloroiodobromide, or silver iodobromide, of varying halide ratios and varying silver concentrations.