US 3271153 A
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ate 10in 3,27l,l5i Patented Sept. 6, 1966 3 271,153 PHOTUGRAPHEC *PhOCEESSlNG BATHS FQR STABILHZATHON PROES1NG Ronald H. Miller and Martin A. Foos, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Ian. 18, 1963, Ser. No. 252,305 6 Claims. (Cl. 96-61) This invention relates to the stabilization of photographic emulsions following the fixing step, particularly in rapid processing processes.
In some situations it is desirable to omit the washing step following development and fixation of a photographic silver halide emulsion. However, it has been difficult to properly stabilize photographic emulsions in order to meet relatively rigid requirements for the processing operation. For instance, it is desirable to have the salt content of the processing bath relatively high to make possible the rapid drying of the processed emulsion, particularly when this emulsion is coated on a paper support.
The salts from the processing bath must not bridge across laps and thus cause blocking of the processed roll. The salts in the final bath must leave no objectionable deposit on the paper or on the drying drum. The bath ingredients must not cause stain on the processed paper, and the bath must be stable and give no excessive sludge upon exhaustion. The components should be readily available and relatively low in cost, and they should be highly soluble so that the solution can be packaged as a liquid concentrate. Moreover, the bath should give no objectionable odor upon drying (such as S fumes) and the solution should be relatively non-toxic and safe to handle.
We have found a stabilizing bath which satisfies the above requirements containing phosphates and sulfites, preferably in combination with an anti-sluding agent.
One object of this invention is to provide a stabilizing bath which can be used to omit the washing step following customary processing using a photographic silver halide developer and a fixing agent. Another object is to provide a rapid processing system employing a stabilizing bath which permits rapid drying of the processed photographic aper, does not cause stain on the processed paper, and is relatively free from objectionable odor and toxicity. An additional object is to provide a stabilizing bath containing a relatively high salt content, the salts of which do not bridge across laps and cause blocking of the processed roll, do not leave objectionable depositions on the photographic emulsion or on the drying drum and which give no excessive sludge upon exhaustion. A still further object is to provide a stabilizing bath having components which are readily available, relatively low in cost and which are highly soluble so that the solution can be pack-aged as a liquid concentrate.
The above objects are attained by using a solution of potassium phosphates and sulfites preferably in combination with an anti-sludging agent. In our preferred composition we use a stabilization solution containing about 15 percent by weight of a mixture of dipotassiurn hydrogen phosphate and potassium dihydrogen phosphate, about 15 percent by weight of potassium sulfite, and about 2 percent by weight of sodium citrate.
In the rapid processing operation, a well-known simple silver halide emulsion is employed, for example, which is exposed and then processed in a developer bath for about 10 seconds, in a first stop bath containing a high concentration of hypo for about 10 seconds, in a second stop bath containing :a high concentration of hypo for about 10 seconds and in a stabilizing bath as described above for about 10 seconds.
A typical stabilizer bath is prepared, for example, as follows:
(1) 500 cc. solution of 16.8% K HPO and 13.2%
KH PO (pH7) (2) 500 cc. 30% K solution (3) 20 grams sodium citrate Water is used as the solvent, but a water soluble volatile solvent such as ethyl alcohol may be added to the solution to expedite drying where the solvent is not deterimental because of vapor disposing problems.
Although the potassium salts are preferable, other alkaline metal salts may be substituted in part. The limiting factors are the required solubility, freedom from salt bridges, and freedom from drum deposits. The range of proportions which are useful in the stabilizing bath are about 15-40 percent by weight dipotassium hydrogen phosphate-potassium di-hydrogen phosphate mixture (pH=7.0-+ -0.8), from 22() percent by weight potassium sulfite and about 03 percent by weight sodium citrate. The total concentration of salt in the stabilizer should be held at 30 percent or above. A lower salt content will result in corresponding slower drying rate.
Other anti-sludge agents than sodium citrate may be used such as, for example, sodium tetraphosphate, potassium tartrate, etc.
The stabilizing bath can be prepared by mixing easily available components which will react together in situ to form the above salts. For instance, phosphoric acid, sodium or potassium bisulfite and potassium hydroxide can be added to the aqueous solution in any order. The phosphate salts and the sulfite salts will then form in the stabilizing bath.
Although our preferred process is intended for rapid processing and stabilization of paper-based silver halide emulsion, this stabilizing bath can be used for photographic emulsions on other supports such as commonly used film bases, aluminum foil and the like. It will also be understood that the term light-sensitive silver halide includes photographic emulsions known in the art as silver chloride, silver bromide, and mixed halide emulsions including iodides, etc. The silver halide developer used is not critical, but may be any of those known in the art.
The following example is intended to illustrate our invention but not to limit it in any way.
Example Coatings of gelatin-silver halide emulsion layers, which had been exposed, were bathed under darkroom con- The sample was then placed in a stop bath containing sodium thiosulfate (hypo), sodium sulfite, and an alum hardener. Following the treatment in the stop bath, the coated photographic emulsion was immersed in a stabilizing bath having the preferred composition described above. No washing step was included. When a similar photographic emulsion was processed using the same system but omitting both the stabilizing and washing steps, the photographic emulsion on the paper base developed stains which detracted from the appearance of the image and 3 which indicated unsatisfactory keeping characteristics. In addition, objectionable salt bridging took place, resulting in blocking in the dried roll.
When other silver halide emulsions are processed using silver halide developers known in the art and in a silver halide solvent bath to remove unexposed silver halide, similar advantages are obtained by stabilizing according to our invention instead of washing the processed emulsion.
It will be understood that this stabilization system can be used to stabilize color emulsions as well as those which are used to make prints by the diffusion process, colloid transfer process and the like. It can be used where the hypo or similar fixing agent is present in the emulsion or contiguous layer, applied from .a solution, for example, in ntonobath systems, etc.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected Within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.
1. A method of rapid processing light-sensitive silver halide emulsion comprising developing an exposed emulsion with a silver halide developer, fixing with a silver halide solvent to remove unexposed silver halide, and stabilizing by imbibing into the emulsion a stabilizing bath containing about 15-40 percent by weight of a mixture of monoand di-basic salts of phosphoric acid and about 220 percent by Weight of a sulfite salt.
2. A method of rapid processing light-sensitive silver halide emulsions comprising developing an exposed emulsion with a silver halide developer, fixing with a silver halide solvent to remove unexposed silver halide and stabilizing by imbibing into the emulsion a stabilizing bat-h containing about 15-40 percent by weight of a mixture of dipotassium hydrogen phosphate and potassium dihydrogen phosphate, 2-20 percent by weight potassium sulfite, and about 3 percent by weight of an anti-sludge agent.
3. A method of rapid processing light-sensitive silver halide emulsions comprising developing an exposed emulsion with a silver halide developer, fixing with a silver halide solvent to remove unexposed silver halide and stabilizing by imbibing into the emulsion a stabilizing bath containing about 1540 percent by weight of a mixture of monoand di-basic salts of phosphoric acid, 2-20 percent by weight of a sulfite salt, and about 0-3 percent by Weight of an anti-sludge agent.
4. A bath for stabilization of developed and fixed photographic silver halide emulsions comprising about 37 to 83 percent by weight of an aqueous solvent, about 15 to 40 percent by weight of a mixture of monoand di-basic salts of phosphoric acid and about 2-20 percent by weight of a sulfite salt.
5. A bath for stabilization of developed and fixed photographic silver halide emulsions comprising about 37 to 83 percent by weight of an aqueous solvent, about 15 to 40 percent by weight of a mixture of dipotassium hydrogen phosphate and potassium dihydrogen phosphate, 2 to 20 percent by weight of potassium sulfite and about 0 to 3 percent by weight sodium citrate.
6. A bath for stabilization of developed and fixed photographic silver halide emulsions consisting essentially of about 37 to 83 percent by Weight of an aqueous solvent, about 15 to 40 percent by weight of a mixture of monoand di-basic salts of phosphoric acid, about 2-20 percent by weight of a sulfite salt and up to about three percent of an anti-sludge agent.
References Cited by the Examiner UNITED STATES PATENTS 2,417,514 3/1947 Neumann 96-56 2,943,935 7/1960 Williver 96-60 FOREIGN PATENTS 805,174 12/1958 Great Britain.
OTHER REFERENCES Ives et al.: J. of Photo. Science, vol. 2, 1954, pp. 7-15.
NORMAN G. TORCHIN, Primary Examiner.
A. D. RICCI, Assistant Examiner.