US3189454A

US3189454A - Method of photographic development and fixing

Info

Publication number: US3189454A
Application number: US145368A
Authority: US
Inventors: George W Luckey; Arthur A Rasch
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1961-10-16
Filing date: 1961-10-16
Publication date: 1965-06-15
Anticipated expiration: 1982-06-15
Also published as: DE1422868A1; GB984157A

Description

June 15, 1965 G. w. LUCKEY ETAL 3,189,454

METHOD OF PHOTOGRAPHIC DEVELOPMENT AND FIXING Filed 00".- 16, 1961 Fi 92L SUPPORT ELATINE LAYER POWDERED MAGNESIUM DE VE LOP/N6 SOLUTION CON TAINING A SEOUESTERING AGENT EXPOSED SILVER HALIDE EMULSION LAYER UPPORT Fig. 2/

16 MA GNESIUM ROLLER -llw EXPOSED SILVER HAUDE EMULSION LAYER CONTAINING n20, DEVELOPING AND 5E0 UESTERING AGENTS 17 m SUPPORT AXES 0F RUBBER ROTATION ROLLER George WEmckey 1N VEN TO S %%WZ M M 1% W,

WRNISYB United States Patent METHOD 0F PHGTOGRAPlH QEVELGFMENT AND FIXING George W. Luclrey and Arthur A. Rasch, Rochester, N.Y., assignors to Eastman Kodak Company, Rochester,

N.Y., a corporation of New Jersey Filed Oct. 16, 1% Ser. No. 145,368 18 Claims. (CI. 96-61) This invention relates to photography and more particularly to a method of developing photographic matcrials.

In the usual method for developing exposed silver halide emulsions, highly alkaline processing solutions are normally employed which begin developing the latent image substantially immediately upon contact with the emulsion layer. In methods of photographic development, it is often desirable to employ more neutral pH solutions and if possible, to control the time at which development will begin even though a processing solution is in contact with the exposed emulsion layer. The present novel photographic developing method accomplishes both of these objectives as well as others having advantages in the processing of photographic materials.

It is, accordingly, an object of the present invention to provide a novel method for processing of photographic materials. Another object is to provide processing solutions for use in said method. A further object is to provide novel photographic materials for use in the novel method of the present invention. Other objects will become apparent from a reading of the following specification and appended claims.

These objects are accomplished by contacting an exposed silver halide emulsion layer with an active metal in the presence of water, a sequestering agent, and a photographic processing agent wherein hydroxyl ion is released to raise the alkalinity of the reacting medium and activate the photographic processing agent present. Without any intention of being limited by a discussion of the reaction involved, it appears that the active metal reacts With water in the presence of a sequestering agent to form the soluble sequestering-agent-metal complex, releasing hydroxyl ions and hydrogen gas.

In accordance with the present invention, the components of the reacting medium must be brought together so that there is a chemical reacting relationship between the active metal, water, and sequestering agent, and sufficient aqueous solution to take up the generating hydroxyl ions and activate the processing agent present. The present invention, accordingly, applies to those photographic processing agents which are active in alkaline solutions and substantially nonactive in neutral or acid solutions. Although a number of such agents are nnown, several of which are later disclosed in this specification, the most widely employed photographic agents of this type are photographic developing agents. Accor ingly, we will direct our attention in thi specification to photographic developing agents and particularly to processing solutions containing such agents.

Development of exposed silver halide emulsion layers according to the invention will now be illustrated by way of the accompanying drawing in which FIG. 1 shows a method of processing comprising contacting an exposed emulsion layer with an active metal incorporating-colloid layer in the presence of an aqueous processing solution containing a sequestering agent and a developing agent.

FIG. 2 of the accompanying drawing shows another method of processing in which an exposed emulsion layer containing water, a sequestering agent and developing agent is passed between a pair of rollers in which the roller contacting the exposed emulsion layer is prepared using an active metal of the present invention.

3,189,454 Patented June 15, 1965 "ice iore particularly, FIG. 1 shows a support 10 having coated thereon a silver halide emulsion layer 11 wherein a powdered active metal IZ carried in a colloid layer 13 on a support 14 is brought into contact with said emulsion layer in the presence of an aqueous processing solution 15 containing a sequestering agent and a developing agent.

in FIG. 2 of the accompanying drawing, a support 10 coated with emulsion layer 124:, which has been previously treated with a processing solution containing a sequestering agent and a photographic developing agent, is developed by passing the material between a pair of

rollers

16 and 17 in which rollers 16 is prepared from an active metal of the invention. The rollers can be rotatably mounted on the axes of rotation 18.

As is well known in the art, photographic developing solutions are of increasingly greater activity as the pH of such solutions rises on the alkaline side of neutrality. Normally, the pH of such solutions, when employed, is in the range from about pH 8.5 to about 12.5 or even higher, depending upon the particular photographic process involved. Developing solutions are likewise less active when the pH of such solutions approaches neutrality or pH 7.6. Normally, at pH 7.0 or slightly below, say, pH 6.5 to 7.0, most developing solutions are in a pH range which is substantially nonactive for fost photographic developing agents. Accordingly, a developing solution incorporating a photographic developing agent can be satisfactorily employed in the present invention and comply with the previously indicated requirement where a pH on the acid side of neutrality is used.

Active metals preferred for complexing with a sequestering agent to generate hydroxyl ions according to the present invention comprise magnesium, zinc, cadmium, aluminum, indium and gallium and alloys of these metals with these active metals or with other less active or nonactive metals. The reaction rate of the present metals and metal alloys with a particular sequestering agent can vary substantially. With a particular sequestering agent, the preferred active metals of the invention are listed in the previous sentence in the order of magnitude of the reaction rate involved, all other factors being equal. In a particular process, it is often desirable to employ particular metals or alloys of metals to control the reaction rate. This is important in many cases because of the hydrogen gas produced by the reaction involved. Accordingly, to prevent deleterious effects in the final print due to gas bubbles at the side of development, various techniques hereinafter discussed can be employed. For example, a magnesium alloy which contains, say, 0.75 percent manganese can be used to replace pure magnesium with optimum efficiency and bubble control. With any of the useful metals or alloys of the invention, it is important to produce suflicient hydroxyl ion for development activity equivalent to that of a conventional developer. Sufiicient hydroxyl ion in a particular solution would of course also be related to the initial pH of the solution, concentration of the addenda, temperature of reaction, etc.

Suitable sequestering agents for use in the present invention can be any such agent which sequesters metal cations during reaction of an active metal with water to form a soluble metal complex, hydrogen gas and hydroxyl ion and prevent formation of the insoluble metal hydroxide. sequestering agents of this type include a wide variety of materials. The preferred sequestering agents have been found to comprise polycarboxylic acids having from about 4 to about 12 carbon atoms and nitrogencontaining 'polycarboxylic acids having from about 4 to about 18 carbon atoms. Typical examples of sequestering agents of these types include, for example, the alkali metal salts (e.g., sodium, potassium and lithium) of citric acid, oxalic acid, tartaricacid, ascorbic acid, aspartic acid, etc.;

and of ethylenediamine tetraacetic acid (ethylenedinitrilo tetraacetic acid), 1,3-diamino-2 propanol tetraace-tic acid, .1,Z-diaminocyclohexaneN,N-tetraacetic acid (e.g., ethylenediamine tetraacetic acid, tetra sodium salt; ethylenediamine tetraacetic acid, tetra potassium salt; ethylenedinitrilo tetraac'etic acid, tetra sodium salt; etc.). The sequestering agents can be used singly or in combination. Other useful sequestering agents have been disclosed in Organic sequestering Agents, by S. Chaberek and A. B. Mai-tell, published 1959, by John A. Wiley and Sons.

In practice, the concentration of sequestering agent in a working solution canvary widely. However, experienc has shown that a concentration of sequestering agent in the range from about 20 grams to about 100 grams per liter of solution gave useful results with a more useful concentration being from about 40 to about 80 grams per liter of working solution.

The sequestering agents of the invention can be employed in their acid or alkali metal salt form since a pH adjustment is normally made prior to use of any composition incorporating these materials.

7 In the present invention also, the sequestering agents can be incorporated in the processing solution, in the emulsion layer, in separate layers placed contiguous to the emulsion layer, or, in a separate processing layer coated on a separate support, such as in web processing, where such a layer is, brought into surface contact with the emulsion layer during processing. In any method employed, it is required, of course, that a sequestering agent be in chemical reactive relationship with an active metal .of the invention and in the presence of water or a processing solution having a pH in.the substantially nonactive pH range prior to release of hydroxyl ions as previously indicated. 7 a

In one method of practice of the present invention, a

{suitable sequestering agent can be dissolved in a photo- Igraphic developing solution which contains only sulficient ,alkali to give a pH in the'range below that which nor- :rnally activates the solution for purposes of photographic development. The developing solution of substantially lnonactive pH is then applied to an exposed'gelatino-silver halide emulsion layer to be processed. The method of application of the processing solution can be any suitable method such as soaking, swabbing, dipping, etc. The exposed layer, so treated, can then be brought into contact with an active metal or metal alloy of the invention to generate hydroxyl ions in the exposed and treated layer to result in development of the photographic latent image. The active metals or alloys of metals of the invention can be applied as a powder, a dispersion or colloid layer containing such a powder, or as a plate, evaporated metals ,on plastics, rollers, and the like. In the use of plates, roller components or processing layers, etc., formed using a metal or metal alloy of the invention, optimum develop- ;ment can be obtained by briefly contacting the treated emulsion layer across the surface of the plate, by abrad- .ing the surface of the plate, by using a porous form or the metal, etc. Optimum developmentcan also be obtained by turning treated emulsion coatings through" fmethods of development, the amount of hydrogen gas 1 formednormally easily escapes from the site of developjment without causing deleterious effects in the emulsion layer.

, Processing solutions of the present invention comprise jsolutions having a substantially nonactive pH and norlanother comprises N-monomethyl-p-aminophenolsulfate;

ildihydroxybenzenes, e.g., dihydroxydiphenyl; hydroqui- 'gfnone compounds, e.g., chlorohydroquinone, dichlorohydroquinone, bromohydroquinone, and dibromohydroquinone; 1-phenyl-3-pyrazolidone and its derivatives, triaminophenols, including 2,4,6-triaminophenol; catechol; pyrogallol; and ene diols. Suitable 3-pyrazolidone developing agents include 1-phenyl-4, 4-dimethyl-3-pyrazolidone, l-p aminophenyl 4-methyl-4-propyl-3-pyrazolidone, and 1-p-chloropheny1-4-methyl-4-ethyl-3- pyrazolidone. Especially useful to the developing compositions comprise mixtures of monomethyl-p-aminophenolsulfate and hydroquinone; 1-phenyl-3-pyrazolidone and hydroquinone; and 4,4-dimethyl-1-phenyl-3-pyrazolidone and hydroquinone.

Processing solutions of the invention can also comprise fixing solutions where fixing agent precursors are cleaved in the presence of alkali to form stabilizing orfixing mercaptans. Typical examples of such materails comprise certain thiol adducts, such as the thiol adducts of chalcone or azomethine compounds, such as p-acetamidothiophenol chalcone adduct, o-aminothiophenol chalcone adduct, mercapto, pivalic acid-chalcone adduct, and pthiocresol-benzal aniline adduct, and certain Michael adducts having the general formula: V

Suitable processing solutions can also comprise combined developing and fixing solutions such as those described in U.S. Patents 2,397,016, March 19, 1946, and 2,525,532, October 10, 1950; solutions comprising developers containing silver halide solvents as described in U.S. 2,371,740, March 20, 1945; and solutions of these types which contain physical development nuclei as described in U.S. 2,698,326, December 28, 1956.

In preparaing the combination developing and fixing compositions, typical examples of fixing agents include alkali metal thiocyanates, alkail metal thiosulfates, ammonium thicyanate, ammonium thiosulfate, thioureas, ammonium cyanide, sodium cyanide, etc. When a compound is toxic, such as sodium cyanide, precaution should be taken to prevent an acid condition which would tend to give off poisonous. cyanide gas.

The emulsions of the invention can be coated in the usual manner on any suitable support, e.g., glass, cellulose nitrate iilm, cellulose ester film, polyvinylacetyl resin film,

those disclosed in U.S. Patents 2,716,062).

The photographic silver halide emulsions useful in the process of our invention can be prepared according to known methods, such as those. described in Hewitson and McClintock, US. Patent 2,618,556, issued November 18, 1952, for example. Of course, emulsions prepared by other methods can be used to equal advantage in this invention. These emulsions can be chemically sensitized or not, as mentioned above. Additional chemi cal sensitizers useful in this invention comprise those disclosed in US. Patent 2,886,437, issued May 12, 1959, in the name of D. E. Piper.

Emulsions of the present invention can contain alkylene oxide polymers, such as those used to sensitize photographic emulsions, such as polymers derived from alkylene oxides composed of from 2 to 4 carbon atoms, e.g., ethylene oxide, propylene oxide and butylene oxide. The preparation of polymers from these compounds is described in Ellis, The Chemistry of Synthetic Resins (1935), pages 990 to 994. The compounds embodying the invention are also referred to sometimes as polyalkylene glycols and their use as sensitizers for silver halide emulsions is described in US. Patents 2,423,549 and 2,441,389.

Various derivatives of alkylene oxides can also be used in accordance with this invention, e.g., condensation prodnets of alkylene oxide with organic compounds containing an active hydrogen atom. Examples of active hydrogen organic compounds, i.e., compounds in which a hydrogen atom may be replaced by reaction of the compound with metallic sodium, methylmagnesium iodide, etc., include alcohols, amines, mercaptans, acids, amides, hydrocarbons, such as acetylene, and compounds having the active hydrogen in a methylene group, such as dibenzoylmethane. More specifically, We may employ condensation products of alkylene oxide with glycols, such as those having from 8 to 18 carbon atoms as described in US. Patent 2,240,472 and British Patent 443,559 as well as condensation products of alkylene oxides with aliphatic alcohols, condensation products of alkylene oxides with aliphatic acids, e.g., lauric acid and glycine, condensation products of alkylene oxides with aliphatic amines or amides, e.g., glycine and lauryl amide, and condensation product-s of alkylene oxides with phenols, e.g., phenol. The preparation of these condensation products is described in U.S. Patent 1,970,578. Condensation products of alkylene oxides with hexitol ring dehydration products as described in US. Patent 2,400,532 can also be employed.

In each case, the polyalkylene oxide or derivative of alkylene oxide should have a molecular weight of at least 300. Condensation products of ethylene oxide with long chain alcohols, acids, amines or amides should have a molecular Weight of about 700. In general, the best results are obtained with the condensation products of ethy ene oxide with organic compounds having an active hydrogen and with ethylene oxide polymers having a molecular weight of 100 to 3500 or more.

The emulsions can also be optically sensitized with cyanine and merocyanine dyes, such as those described in Brooker, US. Patents 1,846,301, issued February 23, 1932; 1,846,302, issued February 23, 1932; and 1,942,- 854, issued January 9, 1934; White, U.S. Patent 1,990,- 507, issued February 12, 1935; Brooker and White, US. Patents 2,112,140, issued March 22, 1938; 2,165,338, issued July 11, 1939; 2,493,747, issued January 10, 1950; and 2,739,964, issued March 27, 1956; Brooker an Reyes, US. Patent 2,493,748, issued January 10, 1950; Sprague, US. Patents 2,503,776, issued April 11, 1950; and 2,519,- 001, issued August 15, 1950; Heseltine and Brooker, US. Patent 2,666,761, issued January 19, 1954; Heseltine, US. Patent 2,734,900, issued February 14, 1956; Van Lare, US. Patent 2,739,149, issued March 20, 1956; and Kodak Limited British Patent 450,95 8, accepted July 15, 1936.

When employing optically sensitized emulsions, the optical sensitizing dyes are advantageously employed in about their usual optimum concentration although concentrations above or below the optimum concentration can be employed.

The addenda which we have described may be used in various kinds of photographic emulsions. In addition to being useful in X-ray and other nonoptically sensitized emulsions, they may also be used in orthochromatic, panchromatic, and infrared sensitive emulsions. They may be added to the emulsion before or after any sensitizing dyes which are used. Various silver salts may 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 agents may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky, US. Patent 2,698,794, issued January 4, 1955; or emulsions'of the mixed-grain type, such as described in Carroll and Hanson, US. Patent 2,592,243, issued April 8, 1952.

The emulsions of the invention can also contain speedincreasing compounds of the quaternary ammonium type as described in US. Patents 2,271,623, February 3, 1942; 2,288,226, lune 30, 1942; 2,334,864, November 23, 1943; or the thiopolymers as described in Graham et al. US. application Serial No. 779,839, filed December 12, 1958, now US. Patent No. 3,046,129; and Dann et al. US. application Serial No. 779,874, filed December 12, 1958, and now US. Patent No. 2,990,699.

The emulsions may also be chemically sensitized with reducing agents such as stannous salts (Carroll, US. Patent 2,487,850), pclyamines such as diethylene triamine {Lowe and Jones, US. Patent 2,518,698), polyamines such as spermine (Lowe and Allen, US. Patent 2,521,925), or bis-(B-am-ineethyl) sulfide and its water-soluble salts (Lowe and Jones, US. Patent 2,521,926).

The emulsions may also be stabilized with the mercury compounds of Allen, Byers and Murray, US. application Serial No. 319,611; Carroll and Murray, US. application Serial No. 319,612; and Leubner and Murray, U.S. application Serial No. 319,613, all filed November 8, 1952, now US. Patents 2,728,663; 2,728,664 and 2,728,665, re-

pectively, granted December 27, 195 5 The emulsions of the invention can also contain other addenda such as gelatin plasticizers (e.g., glycerin, 1,5- pentane diol, ethylene bis(methyl glycolate), bis(ethoxy diethylene glycol)succinate, an acrylic acid ester as described in US. 2,852,386, September 16, 1958, etc.); hardeners for gelatin (e.g., formaldehyde, mucobromic acid, an acid compound as described in US. Patents 2,725,294 and 2,725,295, November 29, 1955, a cyclic 1,2- diketone as described in Allen et al., US. 2,725,305, November 29, 1955, and the like), and coating aids (e.g., saponin, a lauryl monoether of polyethylene glycol as described in Knox et al., US. Patent 2,831,766, April 22, 1958, a salt of a sulfated and alkylated polyethylene glycol ether as described in Knox et al., US. 2,719,087, a water-soluble maleopimarate as described in Knox et al., US. 2,823,123, February 11, 1958, etc.). The dispersing agent for the silver halide can be gelatin or other hydrophilic material such as collodion, albumin, cellulose derivatives and synthetic resins.

These may also be used in emulsions intended for use in difiusion transfer processes which utilize the undeveloped silver halide in the nonimage areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes are described in Rott, US. Patent 2,352,014, issued June 20, 1944, and Land, US. Patents 2,584,029, issued January 29, 1952; 2,698,236, issued December 28, 1954; and 2,543,181, issued Febnuary 27, 1 1; and Y-ackel et al., US. patent application Serial No. 586,705, filed May 23, 1956, and now U.S. Patent No. 3,020,155. They may also be used in color transfer processes which utilize the difiusion transfer of an imagewise distribution of developer, coupler or dye, from a light-sensitive layer to a second layer, while the two layers are in close proximity to one another. Color'processes i this type are described in Land, US. Patents 2,559,643, issued July 10, 1951, and 2,698,798, issued January 4, 1955; Land and Rogers, Belgian Patents 554,933 and 554,934, granted August 12, 1957; International Polaroid, Belgian Patents 554,212, granted July 16, 1957, and 554,935, granted August 12, 1957; Yutzy, US. Patent 2,756,142, granted July 24, 1956, and Whitmore and Mader, US. patent application Serial No. 734,141, filed May 9, 1958, and now abandoned. They may also be used in emulsions intended for use in a monobath process such as described in Haist et al., U.S.Patent 2,875,048, issued February 24, 1959, and in web-type processes, such as the one described in Tregillus et al., US. patent application Serial No. 835,473, filed August 24, 1959.

' The invention will be further illustrated by way of the following examples.

Example 1 A silver chloride emulsion coated on a paper support was exposed to a line negative and bathed for 5 seconds in a solution of the following composition:

After bathing the exposed emulsion stri in the above composition, the emulsion coated layer thereof was placed in surface contact with a magnesium lithographic plate (trademark Zomag-5l and purchased from the Dow Chemical Company) for 40 seconds. A strong image developed in the exposed emulsion layer. The pH of .the layer increased from approximately 6.5 to approximately 10.5 after contact for 40 seconds with themagnesium plate A second control strip of silver chloride emulsion was bathed in the above composition for 5 minutes with no apparent image being developed in the emulsion layer.

After development according to the present example, the photographic paper was fixed and washed in a conventional manner to produce a positive image of good quality. 7 Example 2 A silver bromiodide emulsion coated on a cellulose acetate support was exposed to a step wedge in a conventional manner and bathed in a solution of the following composition:

Grams Phenidone 0.2 Hydroquinone 10.0 Sodidrncitrate 50.0 Sodium sulfite 20.0 Water to make 1.0 liter. .pH 7.0.

Example 3 A strip of Kodak Verichrome Pan Film was exposed ,to an object in a conventional manner and bathed in a solution of the following composition:

I Grams Hydroquinone 20.0 QAscorbic acid. 33.0 Sodium hydroxide 7.5

"Sodium citrate 25.0

i 8 Ethylenediamine tetraacetic acid tetra sodium salt" 25.0 Water to make 1.0 liter. 121-170.

Example 4 A silver chloride emulsion coated on a paper support and containing 175 mg. of hydroquinone, 144 mg. of silver halide, and 260 mg. sodium formaldehyde disulfite per square foot of coated surface was exposed in a well known manner to a line negative and bathed for 5 seconds in a 10 percent aqueous solution of sodium citrate. The emulsion 'side of the coated element was then placed in surface contact with a zinc plate for 45 seconds during which time a moderately strong image developed. A second control emulsion coated strip was treated in a manner similar to the present example except that it was not placed in surface contact with a zinc plate. The sec;- ond control strip did not develop an image in the exposed emulsion layer. 1

' Example 5 A silver chloride emulsion layer having an incorporated hydroquinone developer as in Example 4 wascoated on a paper support, exposed to a line negative, and bathed in a 10 percent aqueous solution of ethylenediamine tetraacetic acid tetra sodium ,salt for .5 seconds. The emulsion side of the element was then placed in contact with a magnesium plate for l0'seconds to produce a strong image by development of silver halide in the exposed emulsion layer. Similar results were obtained in a similar photographic element after treatment for 5 seconds in a 10 percent aqueous solution of sequestering agent according to the present example when the emulsion layer was placed in surface contact with a zinc plate for 45 seconds.

Example 6 Two identical strips of a photographic material as described in'Example 4 were exposed in a well known manner to a line negative and bathed for 2 seconds each in a solution of the following composition:

Each of the above-described emulsion coated strips was then bathed for 5 seconds in 'a solution of the above composition after which one of said strips was placed with the emulsion side in surface contact with a cellular magnesium plate (purchased from the Dow Metal Products Company) for 15 seconds'to produce a strong image by development of the exposed silver halide. The second of the two strips of the example was not placed in contact with the magnesium plate. and no apparent image was produced in the exposed silver halide emulsion layer.

The cellular magnesium plate of the present example was sufiiciently porous to allow some passage. of the above-described treating solution. In another manner of practice of the invention, a hollow cylinder was made from a magnesium plate of, this example wherein the central portion of the cylinder was filled with the above activator solution and stoppered with a rubber plug. By passage of the activator solution through the porous magnesium plate, the bottom surface of the plate became damp such that when drawn across the surface of the exposedemulsion layer at a speed of about 1 foot per minute, a strong image was developed in the emulsion layer.

Example 7 A silver bromiodide emulsion layer coated on a cellulose acetate support was exposed to an object in a conventional manner and bathed for 30 seconds in the following solution:

Grams Hydroq-uinone 20.0 Sodium sulfite 40.0

Ethylenediamine tetraacetic acid tetra sodium salt 30.0 Water to make 1.0 liter. pH 7.0 (adjusted with glacial acetic acid).

The exposed emulsion layer of the filmstrip was then rolled in surface contact with a vacuum evaporated coating of cadmium metal on a plastic support. After about 20 seconds, the two elements were separated and a developed image of good quality was produced in the exposed emulsion layer. A similar control filmstrip was treated in the same manner as the first filmstrip except that it was not placed in contact with the cadmium metal layer and it did not produce a developed image.

Similar results to those obtained in the present example were obtained where evaporated layers of metals such as magnesium, aluminum, zinc, indium and gallium were substituted for the cadmium in the present example. Suitable metals of this type can be coated by vacuum evaporation on various substrates such as paper, glass, or plastic. Alternatively, metal foil paper or plastic laminates can be used.

Example 8 Grams Hydroquinone 10.0 Sodium citrate 40.0

Water to make 1.0 liter.

After the zinc-containing emulsion layer was treated in a solution of the above composition and placed in surface contact with the exposed silver chloride layer of the example for about 1 minute, a good quality developed image was obtained in the exposed emulsion layer.

Similar results can be obtained in which the powdered metal incorporated in the gelatino layer is a metal selected from the group consisting of magnesium, aluminum, cadmium, indium, and gallium.

Suitable concentrations of powdered metals of the present invention in a gelatino emulsion layer as described in the present example normally is in the range, for example, from about 12 to about 120 mg. per square foot of coated surface for magnesium, from about 33 to about 330 mg. per square foot of coated surface for zinc, and from about 56 to about 560 mg. per square foot of coated surface for cadmium. These metal concentrations in coated emulsion layers give good results in minimal processing times without deleterious effects in the processing of silver halide emulsion layers which contain from about to about 500 mg. of silver halide per square foot.

The advantages stemming from the method of processing according to the invention are immediately apparent. For example, the use of neutral processing solutions prior to actual development in photographic processing will eliminate to a large extent the present corrosion problems in photographic processing apparatus which results from the highly alkaline processing solutions now required. The new methods provided by the present invention also make possible decreases in bulk in the weight of processing equipment and materials which can be of prime importance, for example, in aerial processing and processing in limited spaces. Another important advantage of the present invention resides in the fact that processing materials can now be employed which do not require special packaging as heretofore required in high alkali incorporating developing powders to prevent deterioration in shipment and storage. The present invention, accordingly, introduces an important latitude into the materials and methods now available for the processing of photographic materials. It was very unexpected that the method of the present invention could be employed in the processing of photographic materials to an optimum quality and un formity in an acceptable preiod of time without deleterious photographic efiects.

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.

We claim;

1. In a method for processing a photographic element containing at least one light-sensitive hydrophilic colloid layer containing silver halide grains with a latent image comprising the steps of:

(1) development to convert the said latent image to a silver image by contacting said layer with an aqueous alkaline solution of a developing agent, and subsequently (2) fixing the said silver image by contacting the said layer with an aqueous solution of a fixing agent,

the improvement comprising the use of a substantially neutral solution in at least one of the said steps, and supplying substantially all of the hydroxyl ions needed by contacting the said hydrophilic colloid layer of the photographic element with the appropriate processing solution in the presence of at least one metal sequestering agent and at least one metal above hydrogen and not higher than magnesium in the electromotive series of metals.

2. A method of developing an exposed photographic silver halide emulsion layer comprising:

(A) imbibing in said layer an aqueous solution containing:

(l) a silver halide developing agent and (2) at least one sequestering agent, said solution having a pH not substantially greater than about 7.0, and (B) contacting said layer with at least one metal above hydrogen and not higher than magnesium in the electromotive series of metals, to release the hydroxyl ions required to activate the said developing agent and cause development of exposed silver halide into a silver image.

3. The method of claim 1 wherein said metal is ma gnesium.

4. The method of claim 1 wherein said metal is zinc.

5. The method of claim 1 wherein said metal is aluminum.

6. The method of claim 1 wherein said metal is cadmi- 7. The method of claim 1 wherein said metal is indium. 8. ,The method or claim 1 wherein said metal is gallium.

9. The method of claim 1 wherein said sequestering agent is selected from the group consisting of polycarboxylic acids having from about 2 to 12 carbon atoms, and nitrogen-containing polycarboxylic acids having from about 2 to 18 carbon atoms.

10. The method of claim 2 wherein said sequestering agent is citric acid. I

i 11. The method of claim 2 wherein said sequestering agent is tartaric acid.

12. The method of claim Z'Wherein said'sequestering agent is ascorbic acid.

13. The method of claim 2 wherein said sequestering agent is aspartic acid.

f 14. The method 'of claim 2 wherein said sequestering sequestering agent is sodium citrate and the metal is magnesium.

16. The method of claim 2 for'developing an exposed photographic silver halide emulsion layer in which the "sequestering agent is sodium citrate and the metal is me. p

17. The method of claim 2 for developing an exposed photographic silver halide emulsion layer in which the sequestering agent is ethylenediamine tetra-acetic acid tetra sodium salt and the metal is zinc.

18. The method of claim 2 for developing an exposed photographic silver halide emulsion layer in which the sequestering agent is ethylenediamine tetraacetic acid tetra sodium salt and the metal is cadmium.

References Cited by the Examiner UNITED STATES PATENTS OTHER REFERENCES 7 Clerc: Photography Theory and Practice, 2nd ed.,

- page 138, Sir Isaac Pitman and Sons, Ltd.,New York Takibaev: Chemical Abstracts, vol. 49, page 6738.

Roekh: Chemical Abstracts, vol. 49, page 13865 (1955 Remy: Treatise on Inorganic Chemistry, vol. .1, pages 260 and 347, and vol. 2, pages 431 and 446, Elsevier Publishing Co., New York (1956).

Claims

1. IN A METHOD FOR PROCESSING A PHOTOGRAPHIC ELEMENT CONTAINING AT LEAST ONE LIGHT-SENSITIVE HYDROPHILIC COLLOID LAYER CONTAINING SILVER HALIDE GRAINS WITH A LATENT IMAGE COMPRISING THE STEPS OF: (1) DEVELOPMENT TO CONVERT THE SAID LATENT IMAGE TO A SILVER IMAGE BY CONTACTING SAID LAYER WITH AN AQUEOUS ALKALINE SOLUTION OF A DEVELOPING AGENT, AND SUBSEQUENTLY (2) FIXING THE SAID SILVER IMAGE BY CONTACTING THE SAID LAYER WITH AN AQUEOUS SOLUTION OF A FIXING AGENT, THE IMPROVEMENT COMPRISING THE USE OF A SUBSTANTIALLY NEUTRAL SOLUTION IN AT LEAST ONE OF THE SAID STEPS, AND SUPPLYING SUBSTANTIALLY ALL OF THE HYDROXYL IONS NEEDED BY CONTACTING THE SAID HYDROPHILIC COLLOID LAYER OF THE PHOTOGRAPHIC ELEMENT WITH THE APPROPRIATE PROCESSING SOLUTION IN THE PRESENCE OF AT LEAST ONE METAL SEQUESTERING AGENT AND AT LEAST ONE METAL ABOVE HYDOGEN AND NOT HIGHER THAN MAGNESIUM IN THE ELECTROMOTIVE SERIES OF METALS.