United States Patent Office Patented Aug
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3,143,419 United States Patent Office Patented Aug. 4, 1964 2 3,143,419 ventional photographic support and dried. Suitable sup HIGH-SPEED PRNTOUT ERAULSONS CONTAIN ports include, for example, paper, cellulose ester film, NG SLVER GDE AND SLVER OXALATE polyester film, polystyrene, polyethylene, glass, aluminum Paul B. Gilman, Jr., Rochester, N.Y., assignor to Eastman foil, etc. Kodak Company, Rochester, N.Y., a corporation of It has been found that the concentration of silver New Yersey iodide in the finished emulsion can advantageously be No Drawing. Filed June 2, 1960, Ser. No. 33,381 between about 0.03 mole and 0.9 mole per mole of total 3 Claims. (C. 96-50) silver. Maximum sensitivity seems to occur at a silver This invention relates to high-speed, printout photo iodide concentration of about 0.4 mole per mole of total graphic silver salt emulsions and a method for preparing silver. The total concentration of light-sensitive silver them. salts in the finished emulsion will obviously vary, depend ing upon the use intended for the finished emulsion. Two general types of photographic silver halide emul The manner of varying the silver concentration in photo sions are known. The most common type is a develop graphic emulsions is well known to those skilled in the ing-out emulsion. A type of emulsion of less commer 5 art, and it is to be understood that my invention is cial interest is the printout type. The printout effect was susceptible to variations and modifications in emulsions at one time used rather extensively in preparing photo using these well known techniques. graphic positives from a negative by contact printing. The following examples will serve to illustrate more However, the exposures required are quite long, in some fully the method of preparing and using photographic cases as much as 15 to 20 minutes in bright daylight. 20 Consequently, the developing-out emulsions have been emulsions of the printout type which are useful accord investigated and improved upon in speed and stability ing to my invention. much more extensively than the printout type of emulsion. Example 1 The silver halide sensitive salt employed in printout The following solutions were prepared: photographic emulsions is normally silver chloride. 25 These silver chloride emulsions are prepared somewhat (A) differently from developing-out emulsions in that an excess Gelatin--------------------- 20 grams. of soluble silver salt (silver nitrate) is used, rather than Distilled Water--------------- 150 m. an excess of halide, as in the case of developing-out emul SOS. 30 (B) I have now found new photographic silver halide emul Potassium oxalate-monohydrate. 54.2 grams. sions of the printout type which are characterized by quite Distilled Water--------------- 200 m. high speeds, as contrasted with the relatively slow silver halide printout emulsions. The new printout emulsions (C) of my invention comprise silver oxalate and silver iodide. Silver nitrate----------------- 13.5 grams. A portion of the silver iodide can be replaced with an Distilled Water--------------- 150 m. other silver halide, such as silver bromide or silver chlo ride, if desired. They are sensitive principally to blue (D) light and ultraviolet radiation. Potassium iodide.------------- 5.6 grams. It is, therefore, an object of my invention to provide 40 Distilled Water--------------- 150 ml. new printout photographic silver salt emulsions compris ing silver oxalate and silver iodide. Another object is (E) to provide a method of preparing such photographic Distilled water to make.------ 300 grams (total silver salt emulsions. Still another object is to provide weight of emulsion). photographic silver halide emulsions of the printout type 43 which have speeds to tungsten or other artificial light, or The silver nitrate solution (Solution C) was added to daylight, many times higher than conventional printout Solution B and the resulting precipitate was then washed photographic emulsions. Other objects will become ap by decantation. Solution D was then added and the result parent from a consideration of the following description ing mixed precipitate of silver oxalate and silver iodide and examples. 50 was washed by decantation. The precipitate was then The novel photographic silver halide emulsions of my mixed with Solution A at 50° C., and Solution E was invention can be prepared using techniques which have added to bring the total weight of the emulsion up to 300 been previously described in the art of emulsion making. grams. The resulting printout emulsion, which contained Advantageously, I have found that the novel printout about 0.023 mol. of silver oxalate and about 0.034 mol. emulsions of my invention can be prepared by first precip 55 of silver iodide (0.4 mole of silver iodide per mole of itating silver oxalate and subsequenly converting a por total silver) was then coated on an ordinary paper sup port and dried. The photographic emulsion was then tion of the silver oxalate to a silver iodide salt. The exposed to a step wedge using tungsten illumination (No. mixed precipitate of silver oxalate and silver iodide can 2 Photoflood at 117 volts) and was found to have a then be washed by decantation, followed by the addition 60 printout speed approximately eight times faster than a of a suitable binder-colloid, such as a water-permeable, pure silver oxalate emulsion made by method of Example water-insoluble hydrophilic collid, such as gelatin, albu 1 except omitting the addition of Solution D. The men, starch, polyvinyl alcohol, hydrolyzed cellulose ester, emulsion had a spectral response from about 300 to 440 etc. mu with a peak sensitivity at about 415 mu, and a very The prepared emulsion can then be coated on a con 65 sharp cut-off at 440 mu. 3,143,419 3 4. Example 2 described in Heiland U.S. Patent 2,580,427, issued Jan uary 1, 1952. The following solutions were prepared: These silver oxalate-iodide printout materials exhibit Some interesting behavior. In the case of after-treatment (A) exposure of a printout image produced from a low in Potassium oxalate monohydrate. 40 grams. tensity exposure to blue or ultraviolet light, e.g. from a Distilled Water--------------- 200 m. G-E Photoflood lamp No. 2 placed at a distance of one Thiourea solution, 0.001. M----. 5 m. foot for two minutes, the image density and contrast can (B) be markedly increased by a post-exposure to infrared O radiation, e.g., from a 250-watt infrared lamp placed at Silver nitrate----------------- 13.5 grams. a distance of two feet for 15 to 20 seconds, increasing Distilled water--------------- 00 ml, the effective speed by a factor of 20 times. This post Ammonium hydroxide to dissolve exposure intensification of the regular image exposure the precipitate first formed. affords a convenient method to decrease very consider (C) ably the time of printout image exposure required to produce satisfactory image density and contrast. Such Potassium bromide----------- 3.0 grams. post exposure also makes visible certain areas which Potassium iodide------------- 1.0 gram. received some image exposure but too little to result Distilled water--------------- 200 ml. directly in observable image density. Thus, a useful (D) 20 image exposure does not necessarily have to be sufficient to give a visible image directly. Gelatin--------------------- 15 grams. In the case where the image exposure is made with a Distilled water--------------- 100 ml. high intensity, short duration exposure to blue or ultra (E) violet light, e.g., a 900-watt lamp at 3000 K. placed at Distilled water to make------- 300 grams (total 25 a distance of 120 mm. for 0.02 sec., no visible printout weight of emulsion). image was observed and no usable intensification was obtained by infrared post-exposure treatment of the type In preparing Solution B, a small amount of ammonium described above. However, post exposure to a fluores hydroxide was added to form a precipitate of silver cent light source, e.g., Westinghouse 15-watt daylight or hydroxide which was then dissolved by adding just suf 30 G-E 40-watt cool white fluorescent tubes, produced a ficient ammonium hydroxide to solubilize the precipitate. reversal image on which the background darkened rapidly Solution. A was added to Solution B and the resulting to a density much higher than the low density printout precipitate was washed by decantation. Solution C was image, while the latter showed very little increase in then added and the mixed precipitate of silver oxalate density during the post exposure. and silver bromiodide was dispersed in Solution D at 50 While potassium iodide was used as the source of C. and Solution E was added to bring the total weight of iodide ion in the above examples, it is apparent that the emulsion up to 300 grams. The resulting emulsion other water-soluble iodides, such as the sodium salt, am contained 0.025 mole of silver bromide, 0.006 mole of monium salt, etc., can be likewise employed. Also, other silver iodide and about 0.024 mole of silver oxalate. water-soluble silver salts can be employed in place of the The resulting emulsion was then coated on a paper 40 silver nitrate used in the above examples. - Support, dried, and exposed for two minutes to a step It has been found that the sensitivity of ordinary tablet using a No. 2 Photoflood lamp placed at a distance gelatino-silver-iodide emulsions can be increased by sensi of one foot. As in the case of the emulsion in Example tizing these emulsions according to the method shown in 1, this emulsion had a spectral response of from about Staud et al. U.S. Patent 1,925,508, issued September 5, 300 to 440 mp, with a peak sensitivity at 415 mu and a 45 1933.