US3672901A - Process of precipitating silver halide in the presence of a colloid and a water-soluble iron salt - Google Patents

Abstract

A PROCESS FOR PRODUCING A SILVER HALIDE PHOTOGRAPHIC EMULSION INCLUDING A STEP OF PRECIPITATING A SILVER HALIDE IN A COLLOIDAL SOLUTION BY REACTION BETWEEN A HALIDE AND A SILVER SALT, CHARACTERIZED IN THAT SAID PRECIPITATION IS

DONE IN THE PRESENCE OF A WATER-SOLUBLE IRON COMPOUND IN AN AMOUNT OF 10-7 TO 10-3 MOL PER MOL OF THE SILVER SALT CONTAINED IN SAID SOLUTION.

Description

June 27,

DENSITY KINJI OHKUBO ETAL 3,672, 1

PROCESS OF PRECIPITATING SILVER HALIDE IN THE PRESENCE OF A COLLOID AND A, WATEB SOLQBLE I RON SALT Filed May 15; 1970 l-s 2 0 2-5 3'-0 |0g.E ARBITRARY unn (lux. sec.)

INVENTORS KINJI OHKUBO JUNPEI NOGUCHI KUNIOKI OHMURA 6 (7144:, BY z g 1 TTORNEYS United States Patent Office Patented June 27, 1972 3,672,901 PROCESS OF PRECIPITATING SILVER HALIDE [N THE PRESENCE OF A COLLOID AND A WATER- SOLUBLE IRON SALT Kinji Ohkubo, Jnnpei Noguchi, and Kunioki Ohmura, Kanagawa, Japan, assignors to Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed May 15, 1970, Ser. No. 37,618 Claims priority, application Japan, May 17, 1969, 44/ 38,249 Int. Cl. G03c 1/02 us. or. 96-94 16 Claims ABSTRACT OF THE DISCLOSURE A process for producing a silver halide photographic emulsion including a step of precipitating a silver halide in a colloidal solution by reaction between a halide and a silver salt, characterized in that said precipitation is done in the presence of a water-soluble iron compound in an amount of to 10- mol per mol of the silver salt contained in said solution.

This invention relates to a process for production of a photosensitive photographic emulsion for use in a silver halide photographic material, and more particularly, to a process for production of a silver halide photographic emulsion for use in a photographic material which forms a high contrast image.

It has hitherto been known that in order to obtain high contrast silver halide photographic materials, such metal salts as rhodium salts (see FIAT Final Report No. 360), cobalt-cyano complex salts (see US. patent specification 2,517,541) or iridium salts (seen Japanese patent publication No. 4935/68) are added to the solutions employed in making emulsion preparations. Another process for the preparation of high contrast silver halide photographic materials is described in US. patent specification 3,062,647. In this process incorporation of a polyalkylene oxide and a colloid of a noble metal (silver, gold, platinum, palladium) possibly in conjunction with a colloid of a metal sulfide (silver sulfide, zinc sulfide) in a gelatin binder of the silver halide photographic emulsion, will produce the desired photographic materials.

Of the above-cited metal salts effective for obtaining high contrast images, the rhodium salts exhibit remarkable eifects on silver chloride, but have the defect of causing a marked desensitization. The iridium salts only show a marked effect in obtaining high contrast images with flash exposure in a photographic emulsion prepared by precipitating a silver halide at a pH of less than 6.5. Furthermore, the cobalt-cyano complex salts are effec tive on silver chloride, but are toxic and require careful handling.

An object of the present invention is to provide a process for producing a silver halide photographic emulsion of high contrast easily and economically. This process includes a step of precipitating a silver halide in a colloidal solution, such as a gelatin solution, by reaction of a halide with a silver salt. This precipitation is done in the presence of a water-soluble iron compound in an amount of 10* to 10- mols per mol of the silver salt contained in said solution.

The critical featture of the present invention resides in the proportion of the water-solution iron compound to be added to the reaction system. It has unexpectedly been found that the presence of a very small amount of the water-soluble iron compound in the reaction system leads to the preparation of a photographic emulsion capable of forming a high contrast photographic image without a marked reduction in sensitivity.

The iron compounds used in the invention are watersoluble divalent or trivalent iron salts or complex salts.

Specific examples include: ferrous arsenate, ferrous bromide, ferrous carbonate, ferrous chloride, ferrous citrate, ferrous fluoride, ferrous formate, ferrous gluconate, ferrous hydroxide, ferrous iodide, ferrous lactate, ferrous oxalate, ferrous phosphate, ferrous succinate, ferrous sulfate, ferrous thiocyanate, ferrous nitrate, ammonium ferrous sulfate, potassium hexacyanoferrate (II), potassium pentacyanoamine-ferrate (H), basic ferric acetate, ferric albuminate, ammonium ferric acetate, ferric bromide, ferric chloride, ferric chromate, ferric citrate, ferric fluoride, ferric formate, ferric glycero phosphate, ferric hydroxide, acidic ferric phosphate, ferric nitrate, ferric phosphate, ferric pyrophosphate, sodium ferric ethylenedinitrilotetraacetate, sodium ferric pyrophosphate, ferric thiocyanate, ferric sulfate, ammonium ferric sulfate, guanidine ferric sulfate ammonium ferric citrate, potassium hexacyanoferrate (III), tris(dipyridyl) iron (III) chloride, potassium ferric pentacyanonitrosyl, and hexaurea iron (III) chloride.

Of these compounds, hexacyanoferrates (II), hexaeyanoferrates (III), and ferric thiocyanate exhibit especially marked effects.

The iron compound described above is added during the formation of silver halide particles to a gelatin solu tion, a halide solution, or a silver salt solution. It is also possible to add a separately prepared solution of the iron compound to a suspension of a silver halide during the formation of silver halide particles to a gelatin soluprocedures may be employed conjointly. In any of the procedures, it is desirable that an amount of the iron compound to be added is 10* to 10- mol per mol of silver present in the silver salt solution. Amounts of the iron compound below 10 mol scarcely show a high contrast image producing effect, while amounts above 10- mol cause a marked reduction in the photographic sensitivity of the resulting silver halide photographic material.

The silver halide may be silver chloride, silver chlorobromide, silver bromide, silver iodobromide, or silver chloroiodobromide. The use of the iron compound in accordance with the invention is effective for a photographic emulsion prepared by any of the ammonia, neutral or acidic methods to produce a high contrast image. The conventionally known high contrast image producing agents, such as rhodium or iridium salts, may be added together with the iron compound to obtain an additive high contrast image forming effect. In conjunction with these, various metal salts, such as nickel salts, copper salts, zinc salts, cadmium salts, mercury salts, lead salts and thallium salts can also be used to improve the sensitivity or gradation of the photographic emulsion.

A silver halide suspension obtained in accordance with the process of the invention by forming silver halide particles in the presence of an iron compound can be chemically ripened with a usual method. Specifically, the suspension is directly sent to the next chemical ripening step or it is redissolved after setting, shredding, and rinsing with water. In another method, it is coagulated and precipitated with gelatin and then re-dispersed in a solution of gelatin. In the chemical ripening procedure, a suitable noble metal salt, sulfur sensitizer, reduction sensitizer, etc., are added, and the resulting mixture is heated to raise the sensitivity. As such noble metal salts, gold salts, palladium salts, iridium salts, platinum salts, etc., are known. Furthermore, suitable additives, suchas 3 color sensitizers, anti-foggants, wetting agents, or gelatin hardening agents are added, and the finished emulsion is coated on a support and dried. Photographic materials prepared in the absence of an iron compound under the above conditions have a lesser contrast than those materials prepared under these conditions in the presence of '11011. I

A photographic material may also be prepared by adding a developing agent to a gelatin-silver halide photographic emulsion prepared in accordance with the process of the present invention, or by disposing a layer containing a developing agent adjacent to the emulsion layer. Such photographic material is exposed, and developed by contact with an alkaline solution (to be referred to as activator treatment). In this case also, the presence of an iron compound in the preparation of the photographic material enhances contrast in the photographic material.

The process of the present invention exhibits an adwantage that photographic materials of high contrast can be manufactured readily and at low cost.

The invention will further be described by the following examples which are intended to be illustrative rather than limitative.

EXAMPLE 1 Solutions (1), (2), '(3) and (4) of the following recipes were prepared:

Solution (1):

Gelatin: 40 g.

Citric acid: 1.3 g.

Distilled water: 750 g.

Sodium chloride (maintained at 60 C.): 11 g. Solution (2):

A 0.01 wt. percent aqueous solution of potasium hexacyanoferrate (IH): 3 cc.

Solution (3):

Silver nitrate: 20 g.

Distilled water (maintained at 58 C.): 150 cc. Solution (4):

Gelatin: 80 g.

Distilled water (maintained at 60 C.): 200 cc.

Solution (1) was stirred in the dark, and solution (2) was added thereto. Solution (3) was further added over a period of 3 minutes. The resulting mixed solution was left to stand for minutes, and then solution (4) was added. The resulting mixed solution was stirred, and ripened for 90 minutes at 60 C. After ripening, 24 cc. of a 10 wt. percent aqueous solution of formaldehyde was added to the solution to form a coating solution. The coating solution was applied to barvta paper to produce a photographic paper. The amount of the silver halide present in the resulting emulsion layer was 1.8 g./m. calculated as silver.

A photographic paper was prepared in the same manner as described above except that solution (2) was not added. This was a comparative specimen, whereas the photographic paper obtained above was a specimen that comes within the scope of the invention.

These specimens were exposed for $4 second through an optical wedge, and developed for .30 seconds at 20 C. with a developer solution, Papitol (a phenidonehydroquinone type developing agent for photographic paper, product of Fuji Photo Film, Co., Ltd.), followed by fixing, water rinsing, and drying treatments. The photographic image obtained from the photographic material of the invention had a gamma value of 2.28, Whereas the image obtained from the comparative specimen had a gamma value of 1.95.

The photographic characteristic curves of each of these specimens are shown in the accompanying drawing, in which the reflection density of the developed image is plotted against the logarithm of the exposure. In the drawing, curve 1 is a characteristic curve of the specimen in accordance with the invention, while curve 2 is that of the comparative specimen.

It is seen from both of these curves that the photographic emulsion prepared by the process of the invention is excellent in that it improves the gradation of the developed image.

EXAMPLE 2 A photographic emulsion was prepared in the same manner as set forth in Example 1 except that 3 cc. of a 0.01 wt. percent aqueous solution of potassium hexacyanoferrate (H) was used in place of the potassium hexacyanoferrate (III) as solution (2). A photographic paper was prepared using the resulting emulsion. The photographic characteristics of this specimen were measured in the same way as in Example 1, and the gamma value of the developed image was found to be 2.21. Comparison of this specimen with the comparative specimen shown in Example 1 indicates that the emulsion prepared in accordance with the invention is excellent in photographic properties.

EXAMPLE 3 Solutions (1), (2), (3) and (4) of the following recipes were prepared.

Solution (1):

Gelatin: 15 g.

Citric acid: 1.3 g.

Distilled water (maintained at 63 C.): 250 cc. Solution (2):

A 0.01 wt. percent aqueous solution of potassium hexacyanoferrate (H1): 4 cc.

Solution (3):

Silver nitrate: 25 g.

Distilled water (maintained at 60 C.): 200 cc. Solution (4):

Potassium bromide: 8.8 g.

Sodium chloride: 6.8 g.

Distilled water (maintained at 63 C.): 300 cc.

While stirring solution (1) in the dark, solutions (2), (3) and (4) were added simultaneously thereto over a period of 30 minutes. The resulting mixed solution was maintained at 63 C. and left to stand for 5 minutes. With further addition of g. of dry gelatin, the mixture was allowed to stand for 60 minutes, followed by addition of 24 cc. of :a 10 wt. percent aqueous solution of formaldehyde to form a coating solution. The coating solution was applied to baryta paper to produce a photographic paper. The amount of the silver halide present in the resulting emulsion layer was 2.1 g./rr.l. calculated as silver. A comparative sample [was prepared in the same way as above except that the solution (2) was not added.

Both of these specimens were exposed for $4 second through an optical wedge, and developed for 30 seconds at 20 C. with the Papitol developer solution set forth in Example 1, followed by fixing, water rinsing, and drying treatments. The photographic properties of both samples were examined in the same manner as in Example 1. As a result, it was found that the specimen prepared in accordance with the present invention had a gamma value of 1.70, whereas the comparative specimen had a gamma value of 1.39. This indicates a good elfect of the present invention.

EXAMPLE 4 A photographic paper was prepared in the same manner as set forth in Example 3 except that 4 cc. of a 0.01 wt. percent aqueous solution of potassium hexacyanofer-rate (II) was used instead of the potassium hexacyanoferrate (III) as solution (2). The photographic paper was treated in the same way as in Example 3 to form a photographic image. The developed image had a gamma value of 1.67.

LEXAM PLE 5 A photographic paper was prepared in the same way as set forth in Example 3 except that 4 cc. of a 0.01 wt.

percent of aqueous solution of ferric thiocyanate was used instead of the potassium hexacyanoferrate (III) as solution (2). The photographic paper was treated in the same way in Example 3 to form a photographic image. The developed image had a gamma value of 1.60.

EXAMPLE 6 Solutions (.1), (2), (3) and (4) of the following recipes were prepared.

Solution l Gelatin: 10 g. Potassium iodide: 0.8 g. Aqueous ammonia (ION): 18 cc.

Distilled water (maintained at 48 C.): 430 cc. Solution (2):

A 0.01 wt. percent aqueous solution of potassium hexacyanoferrate (III): 7 cc. Solution (3):

Silver nitrate: 80 g. Distilled water (maintained at 45 C.): 300 cc. Solution (4):

Potassium bromide: 33.6 g. Sodium chloride: 16.8 g. Aqueous solution of ammonium rhodium chloride (0.01% by weight): 0.5 cc. Distilled water (maintained at 48 C.): 350 cc.

While stirring solution (1) in the dark, solutions (2), (3) and (4) were added simultaneously over a period of 50 minutes. Immediately, sulfuric acid was added to adjust the pH of the mixed solution to 4.5. The solution was allowed to stand for 20 minutes at 48 C. With further addition of 110 g. of dry gelatin, the solution was allowed to stand for 30 minutes. The resulting emulsion was cooled to gelati'on, shredded, and then washed with cold water for one hour. The emulsion was heated to 60 C. to redissolve gelatin, and the pAg value was adjusted to 7.2 by addition of an aqueous solution of cadmium chloride. With further addition of a sensitizer, 5 cc. of a 0.01 wt. percent aqueous solution of tetrachloroaurate (III), the emulsion was left to stand for 60 minutes, followed by addition of 24 cc. of a wt. percent aqueous solution of formaldehyde to form a coating solution. The coating solution was applied to baryta paper. The amount of the silver halide present in the formed emulsion layer was 2.0 g./m. calculated as silver.

A comparative specimen was prepared in the same manner as described above except that solution (2) was not added.

These specimens were exposed for second through an optical wedge, and developed for 2 minutes at C. with the Papitol developer described above, followed by fixing, water rinsing, and drying treatments. An image obtained from the specimen of the invention has a gamma value of 1.87, whereas that obtained from the comparative specimen had a gamma value of 1.5-8.

EXAMPLE 7 Two photographic emulsions (specimen of the invention and comparative specimen) were prepared in the same manner as set forth in Example 6, Hydrochloric acid was added to each of the emulsions to adjust its pH to 4.0. 30 grams of hydroquinone was added per kilogram of the emulsion, and 24 cc. of a 10 wt. percent aqueous solution of formaldehyde was added to baryta paper.

These two specimens were exposed for $5 second, and developed and stabilized using a Quick Copy Treating Solution and a Quick Industrial Processor (both being the products of Fuji Photo Film Co., Ltd., Japan). An image obtained from the specimen of the invention had a gamma value of 1.65, whereas that obtained from the comparative specimen had a gamma value of 1.30.

As is clear from the foregoing examples, the present invention exhibits excellent effects in any specific embodi- 6 ments and is very useful in improving the quality of photographic images.

What is claimed is:

1. A process for producing a silver halide photographic emulsion consisting essentially of precipitating silver halide particles in a colloidal solution by reacting a silver salt and a halide in the presence of, during said precipitation step, from 10"" to 10- mole, per mole of the silver salt, of a water-soluble iron compound.

2. The process of claim 1 wherein said colloidal solution is produced by mixing separate solutions of said halide, said silver salt and a colloidal material.

3. The process of claim 2 wherein said colloidal material is gelatin.

4. The process of claim 2 wherein said water-soluble iron compound is added to said solution of said colloidal material prior to said mixing step.

5. The process of claim 2 wherein said water-soluble iron compound is added to said halide solution prior to said mixing step.

6. The process of claim 2 wherein said water-soluble iron compound is added to said silver salt solution prior to said mixing step.

7. The process of claim 1 wherein said silver halide emulsion is a gold-sensitized emulsion.

8. The process of claim 1 further comprising adding to said silver halide photographic emulsion a developing agent and developing the resulting photographic material by contacting said photographic material with an alkaline solution.

9. The process of claim 1 wherein said water-soluble iron compound is a divalent or trivalent iron salt or a complex salt of an iron.

10. The process of claim 1 wherein said water-soluble iron compound is a hexacyanoferrate (II), a hexacyanoferrate (III) or a ferric thiocyanate.

11. The process of claim 3 wherein said water-soluble iron compound is a hexacyanoferrate (II), a hexacyanoferrate (III) or ferric thiocyanate.

12. The process of claim 1 wherein said water-soluble iron compound is selected from the group consisting of ferrous arsenate, ferrous bromide, ferrous carbonate, ferrous chloride, ferrous citrate, ferrous fluoride, ferrous formate, ferrous gluconate, ferrous hydroxide, ferrous iodide, ferrous lactate, ferrous oxalate, ferrous phosphate, ferrous succinate, ferrous sulfate, ferrous thiocyanate, ferrous nitrate, ammonium ferrous sulfate, potassium hexacyanoferrate (II), potassium pentacyanoamine-ferrate (II), basic ferric acetate, ferric albuminate, ammonium ferric acetate, ferric bromide, ferric chloride, ferric chromate, ferric citrate, ferric fluoride, ferric formate, ferric glycero-phosphate, ferric hydroxide, acidic ferric phosphate, ferric nitrate, ferric phosphate, ferric pyrophosphate, sodium ferric ethylenedinitrilotetraacetate, sodium ferric pyrophosphate, ferric thiocyanate, ferric sulfate, ammonium ferric sulfate, guanidine ferric sulfate, ammonium ferric citrate, potassium hexacyanoferrate (III), tris(dipyridyl) iron (III) chloride, potassium ferric pentacyanonitrosyl, and hexaurea iron (III) chloride.

13. A silver halide photographic emulsion produced by the process of claim 1.

14. A process for producing a silver halide photographic emulsion consisting of precipitating silver halide particles in a gelatin solution by reacting a silver salt and a halide in the presence of, during said precipitation step, from 10- to 10 mole, per mole of the silver salt, of a water-soluble iron compound.

15. The process of claim 14 wherein said silver salt is silver nitrate.

16. The process of claim 14 wherein said water-soluble iron compound is a hexacyanoferrate (II), a hexacyano ferrate (III) or ferric thiocyanate.

(References on following page) 7 8 References Cited FOREIGN PATENTS UNITED STATES PATENTS 911,488 11/1962 Great Britain 96114.7

2,540,085 2/1951 Baldsiefen 96-108 I 2,618,556 11/1952 Hewitson 96-414.? 5 NORMAN TORCHIIL Pnmary Exammer 3,178,289 4/1965 Sottysiak 96114.7 J. R. HIGHTOWER, Assistant Examiner 3,418,122 12/1968 0011 96-108 3,449,125 6/1969 Bigelow 96-108 US. Cl. X.R. 3,531,289 9/1970 Wood 96-94 -11 1 3,531,291 9/1970 Bacon 96-94 10

Images