US3512982A - Nucleic acids as fog stabilizers for photographic emulsions - Google Patents

Description

United States Patent 3,512,982 NUCLEIC ACIDS AS FOG STABILIZERS FOR PHOTOGRAPHIC EMULSIONS Robert C. Taber, William H. Russell, and Charles A. Golie, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Apr. 6, 1967, Ser. No. 628,830 Int. Cl. G03c 5/30, 1/34 US. Cl. 96-665 12 Claims ABSTRACT OF THE DISCLOSURE A photographic silver halide emulsion or photographic element containing a fog-stabilizing amount of a nucleic acid, e.g., ribonucleic acid or deoxyribonucleic acid. Developing photographic elements in the presence of a nucleic acid is also described.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to new and improved antifoggants and stabilizers for photographic elements and to photographic silver halide emulsions containing said antifoggants and stabilizers therein. The invention also relates to a process of developing photographic elements in the presence of new and improved antifoggants.

Description of the prior art During development of a silver halide emulsion, small amounts of silver halide are reduced to metallic silver re gardless of whether or not they have been exposed. This reduction of silver ion produces a background fog which is more specifically referred to as chemical fog. This fog is particularly noticeable when the film is given more development than intended either because of longer processing time or higher processing temperature or a combination of both.

Chemical fog, apparent in most silver halide systems, has been reduced by prior art methods of processing exposed silver halide amaterial in the presence of compounds which restrict development of unexposed silver halide. Such compounds can be incorporated in the silver halide emulsion or in the processing solutions for developing such silver halide emulsions. Compounds which have been found to have a chemical fog inhibiting effect on emulsions which have been subjected to high temperature and high humidity conditions are referred to as emulsion stabilizers. On the other hand, compounds which have been found to have chemical fog inhibiting effects on emulsions which have not been exposed to adverse storage conditions are referred to as antifoggants. Although a large number of emulsion stabilizers and antifoggants have been used in the prior art, many of these compounds cause undesirable losses in emulsion speed and contrast and others lack adequate compatibility with emulsion gelatin. Some addenda which have been used in the past to control extended development fog have the disadvantage of attacking the latent image. For example, mercuric chloride added to a photographic emulsion controls fog but results in loss of density if the exposed film is not processed soon after exposure.

SUMMARY OF THE INVENTION According to one embodiment of this invention, there is incorporated into the silver halide emulsion of a photographic element or in a layer contiguous to the silver halide emulsion, a fog-stabilizing amount of a nucleic acid. The nucleic acid stabilizes the emulsion against fog when Patented May 19, 1970 ice DESCRIPTION OF THE PREFERRED EMBODIMENTS The nucleic acid may be incorporated into the silver halide emulsion of a photographic element or in a layer contiguous to the silver halide emulsion in any amount which will stabilize the silver halide emulsion against fog. In general, a concentration of the nucleic acid in an amount of from about 0.025 to about 10, preferably about 0.050 to about 2, grams per mole of silver in the silver halide emulsion can be used with good results.

Nucleic acids are made up of three components, liberated on acid hydrolysis: an organic base or bases, phosphoric acid and a sugar. As far as is known, the sugar unit is either ribose or 2-deoxyribose. Both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) contain the bases adenine, guanine and cytosine. In DNA, the fourth base is thymine while in RNA the fourth base is uracil. In our invention, either DNA alone, RNA alone or mixtures of DNA and RNA can be employed.

The preparation of photographic silver halide emulsions such as are suitably stabilized with a nucleic acid typically involves three separate operations: (1) emulsification and digestion of silver halide, (2) the freeing of the emulsion of excess Water-soluble salts, suitably by washing with water, and (3) the second digestion or after-ripening to obtain increased emulsion speed or sensitivity. (Mees, The Theory of the Photographic Process, 1954.) The nucleic acid can be added to the emulsion before the final digestion or after-ripening or it can be added immediately prior to the coating.

The silver halide emulsion of a photographic element containing the antifoggants of this invention can contain conventional addenda such as gelatin plasticizers, coating aids, antifoggants such as the azaindines and hardeners such as aldehyde hardeners, e.g., formaldehyde, mucochloric acid, glutaraldehyde bis(sodium bisulfite), maleic dialdehyde, aziridines, dioxane derivatives and oxypolysaccharides. Sensitizing dyes useful in sensitizing such emulsions are described, for example, in US. Pats. 2,526,632 of Brooker and White issued Oct. 24, 1950, and 2,503,776 of Sprague issued Apr. 11, 1950. Spectral sensitizers which can be used are the cyanines, merocyanines, complex (trinuclear) cyanines, complex (trinuclear) merocyanines, styryls, and hemicyanines. Developing agents can also be incorporated into the silver halide emulsion if desired or can be contained in a separate underlayer. Various silver salts can be used as the sensitive salt such as silver bromide, silver iodide, silver chloride, or mixed silver halides such as silver chlorobromide or silver bromoiodide.

The silver halide emulsion layer of a photographic element containing the antifoggants of the invention can contain any of the hydrophilic, water-permeable binding materials suitable for this purpose. Suitable materials include gelatin, colloidal albumin, polyvinyl compounds, cellulose derivatives, acrylamide polymers, etc. Mixtures of these binding agents can also be used. The binding agents for the emulsion layer of the photographic element can also contain dispersed polymerized vinyl compounds. Such compounds are disclosed, for example, in US. Pats. 3,142,568 of Nottorf issued July 28, 1964; 3,193,386 of White issued July 6, 1965; 3,062,674 of 3 Houck, Smith and Yudelson issued Nov. 6, 1962; and 3,220,844 of Houck, Smith and Yudelson issued Nov. 30, 1965; and include the water-insoluble polymers of alkyl acrylates and methacrylates, acrylic acid, sulfoalkyl acrylates or methacrylates and the like.

4 halide emulsion layer. Such processes are described in US. Pats. 2,352,014 of Rott issued June 20, 1944; 2,543,181 of Land issued Feb. 27, 1951; and 3,020,155 of Yackel, Yutzy, Foster and Rasch issued Feb. 6, 1962. The emulsions can also be used in diffusion transfer color The silver halide emulsion of a photographic element 5 processes which utilize a diffusion transfer of an imagecontaining the antifoggants of the invention can be coated Wise distribution of developer, coupler or dye, from a on a wide variety of supports. Typical supports are cellulight-sensitive layer to a second layer, while the two laylose nitrate film, cellulose ester film, polyvinyl acetal film, ers are in close proximity to one another. polystyrene film, poly(ethylene terephthalate) film and While it is preferred to utilize the antifoggants of the related films or resinous materials as well as glass, paper, invention by incorporating them directly into a photometal and the like. Supports such as paper which are graphic element, the antifoggants could also be utilized coated with a-olefin polymers, particularly polymers of by incorporating them into a photographic developer, a-olefins containing two or more carbon atoms, as exemsince image formation would still take place in the presplified by polyethylene, polypropylene, ethylene-butene ence of the antifoggants and they would still perform their copolymers and the like can also be employed. antifoggant function.

The speed of the photographic emulsions containing The antifogging agents of this invention can be inthe antifoggants of the invention can be further increased corporated to advantage during manufacture in silver by including in the emulsions a variety of hydrophilic colhalide emulsions representing the variations described loids such as carboxymethyl protein of the type described above. Moreover, fog control in binderless silver halide in US. Pat. 3,011,890 of Gates, Jr., Miller and Koller films prepared by vapor deposition of silver halide on 21 issued Dec. 5, 1961, and polysaccharides of the type desuitable support can be achieved by coating the antiscribed in Canadian Pat. 635,206 of Koller and Russell fogging agents of the invention over the vapor deposited issued J an. 23, 1962. layer of silver halide.

Photographic emulsions containing the antifoggants of 25 The invention can be further illustrated by the followthe instant invention can also contain speed-increasing ing examples or preferred embodiments thereof; although compounds such as quaternary ammonium compounds, it will be understood that these examples are included polyethylene glycols or thioethers. Frequently, useful efmerely for purposes of illustration and are not intended fects can be obtained by adding the aforementioned speedto limit the scope of the invention. increasing compounds to the photographic developer solutions instead of, or in addition to, the photographic emul- EXAMPLE 1 sions. Separate samples of a silver chlorobromide emulsion Photographic elements containing the antifoggants of containing, respectively, no antifoggant, HgCl and vary the invention can be used in various kinds of photoing amounts of RNA are ripened to optimum sensitivity graphic systems. In addition to being useful in X-ray and and coated on a cellulose acetate film support at a covother non-optically sensitized systems, they can also be erage of 478 milligrams of silver per square foot and 474 used in orthochromatic, panchromatic and infrared sensimilligrams of gelatin per square foot. One set of film tive systems. The sensitizing addenda can be added to coatings is exposed for 10* second on an intensity scale photographic systems before or after any sensitizing dyes sensitometer, processed for three minutes in Kodak D-19 which are used. Developer containing 10 milligrams of potassium iodide Silver halide emulsions containing the antifoggants of per liter, fixed, washed and dried. The procedure is rethe invention can be used in color photography, for expeated with a second set of film coatings except that the ample, emulsions containing color-forming couplers or film coating is processed for eight minutes in the deemulsions to be developed by solutions containing couveloper. A third set of film coatings exposed three days plers or other color-generating materials, emulsions of the 5 earlier and kept at 78 F. is processed for three minutes mixed-packet type such as described in US. Pat. 2,698,794 in the developer, fixed, washed and dried. The photoof Godowsky issued Jan. 4, 1955; in silver dye-bleach graphic results obtained from these tests are set forth systems; and emulsions of the mixed-grain type such as in Table I. In this table, D is the loss in density of film described in US. Pat. 2,592,243 of Carroll and Henson coatings which have been kept at 7 8 F. for three days issued Apr. 8, 1952. after an exposure which produces a fresh density of 1.0;

Silver halide emulsions containing the antifoggants of and D is the loss in density of film coatings which have the invention can be sensitized using any of the wellbeen kept at 78 F. for three days after an exposure known techniques in emulsion making, for example, by which produces a fresh density of 2.0.

TABLE I Gone. in 3 minute processing 8 minute "mg/mole processing, Compound Ag Rel. speed Gamma Fog Fog Dr Dz 214 4. 30 0. 22 0. 74 0. 12 0. 20 180 4. 30 0.08 0. 10 0. 24 0. 44 19s 4. 10 0. 0s 0. 35 0. 12 0. 22 190 3. 90 0. 05 0. 24 0.14 0.18 186 3. 76 0. 0s 0. 21 0.06 0. 13 182 3. 44 0. 04 0. 20 0. 10 0. 12 17s 3. 44 0. 04 0. 19 0. 05 0. 09

digesting with naturally active gelatin or various sulfur, selenium, tellurium compounds and/or gold compounds. The emulsions can also be sensitized with salts of noble metals of Group VIII of the Periodic Table which have an atomic Weight greater than 100.

The results in the above table show that RNA compares favorably with HgCl in its ability to control extended development fog that it shows less tendency to attack the latent image as evidenced by the resistance to density loss (D and D for RNA as compared to the mercuric chlo- Silver halide emulsions containing the antifoggants of ride salt.

the invention can be used in diffusion transfer processes which utilize the undeveloped silver halide in non-image areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a silver EXAMPLE 2 This example illustrates the use of RNA as an antifoggant in a high speed silver halide emulsion of the type receiving layer in close proximity to the original silver used in medical X-ray films. Two silver bromoiodide emulsions, one containing no antifoggant and the other containing RNA, are coated on a polyethylene terephthalate film support at a coverage of 454 milligrams of silver per square foot and 504 milligrams of gelatin per square foot. The coatings are given a 5 second simulated blue screen exposure and processed for six minutes in Kodak D-l9 Developer containing 10 milligrams of potassium iodide per liter. A second set of coatings, which have been incubated for two weeks at 120 F. and 50 percent relative humidity, are processed in the same manner. The photographic results obtained from these tests are set forth in Table II.

The results in Table H show that RNA controls incubation fog without adversely aifecting sensitometric properties.

EXAMPLE 3 A silver bromoiodide emulsion is prepared corresponding to Emulsion No. 12 described in Empirical Relations Between Sensitometric and Size-Frequency Characteristics in Photographic Emulsion Series by Trivelli and Smith, Photo. Journal, May 1939, page 330. Two samples of this emulsion, one (the control) containing no antifoggant and the other containing 1.0 gram of RNA per mole of silver, are coated on a cellulose acetate film support at a coverage of 450 milligrams of silver and 1030 milligrams of gelatin per square foot. A sample of each film coating is exposed for second on an intensity scale sensitometer, processed for five minutes in Kodak Developer DK- 50, fixed, washed and dried. The photographic results obtained are listed in Table III.

TABLE III Relative Antifoggant speed Gamma Fog The results in Table III show that RNA gives antifoggant action and allow chemical sensitization to a higher speed.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected Without departing from the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

We claim:

1. A composition comprising a photographic silver halide emulsion containing a fog-stabilizing amount of ribonucleic acid or deoxyribonucleic acid.

2. The composition of claim 1 wherein said nucleic acid, ribonucleic acid or deoxyribonucleic acid, is present in an amount of from about 0.025 to about 10 grams per mole of silver in said silver halide emulsion.

3. A photographic element comprising a support coated with a silver halide layer, said element containing a fog-stabilizing amount of ribonucleic acid or deoxyribonucleic acid.

4. The photographic element of claim 3 wherein said layer is a silver halide emulsion.

5. The photographic element of claim 4 wherein said nucleic acid, ribonucleic acid or deoxyribonucleic acid, is present in an amount of from about 0.025 to about 10 grams per mole of silver in said silver halide emulsion.

6. The photographic element of claim 4 wherein said nucleic acid, ribonucleic acid or deoxyribonucleic acid, is present in said silver halide emulsion.

7. The photographic element of claim 4 wherein said nucleic acid is present in a layer contiguous to said silver halide emulsion.

8. The photographic element of claim 7 wherein said ribonucleic acid or deoxyribonucleic acid is present in said silver halide emulsion.

9. In a process of developing a photographic element comprising a support coated with at least one silver halide emulsion layer, the improvement comprising developing said photographic element in the presence of a stabilizing amount of ribonucleic acid or deoxyribonucleic acid.

10. The composition of claim 1 containing a fogstahilizing amount of ribonucleic acid.

11. The photographic element of claim 3 containing a fog-stabilizing amount of ribonucleic acid.

12. The process of claim 9 in which the improvement comprises developing said element in the presence of ribonucleic acid.

US. Cl. X.R. 96-109 Disclaimer 3,512,982.-R0bert U. Taber, William H. Russell, and Charles A. Gofie, Rochester, N.Y. NUCLEIC ACIDS AS FOG STABILIZERS FOR PHO- TOGRAPHIC EMULSIONS. Patent dated May 19, 1970. Disclaimer filed Apr. 5, 1971, by the assignee, Eastman Kodak Company. Hereby enters this disclaimer to claims 1 through 12, inclusive.

[Ofiimkzl Gazette June 29, 1971.]

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