US 3179517 A
Description (OCR text may contain errors)
April 20, 1955 L. w. TREGILLUS ETAL 3,179,517
WEB PROCESSING METHOD AND COMPOSITION Filed Aug. 24, 1959 2 Sheets-Sheet 1 Fig.
EDWIN E WYA/VD, Jr.
LEONARD W TREG/LLUS ARTHUR A. RJASCH INVENTORS A T TORNE Y5 Aplll 20, 1965 w. TREGILLUS ETAL 3,179,517
WEB PROCESSING METHOD AND COMPOSITION Filed Aug. 24, 1959 2 Sheets-Sheet 2 Fig. 2
EDWIN B. WYA/VD, J5 LEONARD w TREG/LLUS ARTHUR A. RASCH INVENTORS ATTORNEYS United States Patent 3,179,517 WEB PRQCESSENG METHGD AND COMPUSITION This invention relates to improvements in the development and fixation of photographic images in silver halide emulsion layers and more particularly, to a method in which a siliver halide emulsion layer containing a latent photographic image is developed and fixed in one operation by intimately contacting the emulsion layer with a hydrophilic processing layer or web containing an aqueous processing solution and a silver-precipitating agent.
The elimination of conventional photographic processing baths was suggested by Westermann in Swiss Patent 155,331, issued June 16, 1926. This was to be accomplished by the successive use of developing and fixing films composed of a suitable support, such as cellulose acetate, coated with a gelatin layer containing either a developing or a fixing solution. In use a developer film was pressed in contact with a previously moistened photographic plate containing a latent image. When development was complete, the developing film was removed and the plate washed in water. The developed plate was then treated with a fixing sheet in a similar manner and subsequently given a final water wash. This procedure was intended to obviate the necessity for transporting large volumes of processing solutions when the photographer desired to process his plates in the field. The
Westermann invention has not come into widespread use in spite of the alleged advantages. Later Rott, in US. Patent 2,352,014, issued June 20, 1944, suggested the now familiar solvent transfer process by means of which a photographic image in a silver halide emulsion layer is converted to a reversed image on an inert reception material. In the Rott process the photographic emulsion layer is impregnated with a developer after exposure to light and pressed in contact with an inert reception material in the presence of a silver halide solvent and a fogging agent. The undeveloped silver halide in the emulsion layer is transferred by the silver halide solvent to the reception layer where the silver is deposited to produce the desired reversed image. The Rott solvent transfer method and other methods of this type have generally been employedto obtain a positive photographic image in the reception layer, the original emulsion layer or negative being discarded. Additional prints have customarily been made from the positive image in the reception layer by known methods rather than from the negative since the latter is normally of inferior photographic quality due, among other things, to incomplete fixation.
It is an object of the present invention to provide a one-step method for substantially completely developing and fixing a photographic image in a silver salt emulsion layer to obtain a stable silver image of acceptable photographic quality in the original emulsion layer without immersion in photographic processing baths.
It is another object of the invention to provide such a process in which substantially all of the undeveloped silver halide is removed from the silver halide emulsion layor with substantially less silver halide solvent than would be required for this purpose if the element were processed in a photographic fixing bath.
It is a further object of the invention to provide a one.- step method for the rapid processing of silver halide sensitized photographic film to produce a substantially fully 3,179,517 Patented Apr. 20, 1965 developed and fixed negative of good photographic quality stable on storage without further treatment. and adapted to be viewed directly or used for the production of photographic prints by conventional means.
It is still another object of the invention to provide processing elements or webs capable of being used repeatedly in the development and fixation of silver salt images in photographic emulsion layers.
These and other objects of the present invention which will be apparent from the detailed description below are attained by processing a silver halide emulsion layer containing a latent photographic image by intimate contact with a hydrophilic organic colloid processing element or web separable from the emulsion layer. This processing element contains dispersed silver precipitating agent, and at least at the time of contact with the exposed emulsion layer, sufficient processing solution to develop the exposed silver halide and to remove substantially all of the undeveloped silver halide. The processing solution contains silver halide developing agent, an organic aminesulfur dioxide addition product, and silver halide solvent or fixing agent. The processing element is maintained in intimate contact with the silver halide emulsion layer until development of the latent image is substantially complete and substantially all of the undeveloped silver halide has been cleared from the emulsion layer by the silver halide solvent and deposited in the processing element by the silver halide precipitating agent. Precipitating agents for the purpose of this invention are either nuclei or development centers on which silver from a soluble silver halide complex can be precipitated as metallic silver by physical development, or compounds which react with the silver of the soluble silver halide complex to form an insoluble silver compound. The processing element is then separated from the substantially completely developed and fixed emulsion layer which requires no further processing of any kind, either washing or stabilization, for usual photographic purposes although it the processed element is to be kept for achival purposes it may be advantageous to employ a short water wash. The resulting fully processed photographic element is of acceptable photographic quality. In fact, due to edge effects resulting from still development, and the particular type of processing solution formulation, the image in a negative processed by the new method will often be sharper than the image in an indentical negative processed in conventional agitated developing and fixing baths.
As noted above, the art has developed a number of photographic processing methods which eliminate the necessity for employing conventional developing and fixing baths or, for example, a combined developing and fixing solution. Many of these methods fail either in not giving adequate development of latent images in silver halide emulsion layers or in not giving adequate fixation. In general, this is due to the fact that large amounts of silver halide solvent are required to assure complete fixation and the available supply of this solvent is necessarily limited by the. capacity of the photographic elements employed. In many instances the effective photographic sensitivity is also considerably lower with. conventional combined developing and fixing compositions than with the process of our invention comprising contacting the emulsion with a hydrophilic layer or Web containing aqueous processing solution and a silver precipitating agent. An additional problem is introduced with the necessity for employing large amounts of silver halide solvent in that a subsequent washing operation is required to remove the soluble silver salt normally formed. These disadvantages are overcome in the present invention by incorporation of a silver halide precipitating agent in the body of the processing element. For example, when nuclei for physical development are incorporated in the processing web, the silver from the salts formed by fixation is precipitated on the nuclei in the web thus releasing the silver halide solvent, in which the silver halide was taken up and transferred to the processing element, so that it may transfer additional undeveloped silver halide from the emulsion layer. Therefore, less silver halide solvent is required in the method of the present invention since a relatively small amount of solvent is reused repeatedly. The necessity for a final wash to eliminate soluble silver salts is also eliminated for practical purposes since the undeveloped silver halide is precipitated in the web. As noted previously, a short water wash may be employed when it is desired to preserve the processed photographic elements as permanent records.
The novel processing method of the present invention is applicable to the development and fixation of all types of silver halide-sensitized photographic elements including photographic plates, films and the like and is especially suitable for processing long strips of film such as strips of microfilm or motion picture film. The processing elements or webs of the invention may take any suitable form or shape. For example, they may consist of pads, sheets, strips or webs of hydrophilic material either unsupported or coated on suitable supports such as glass, metal, paper, polyethylene, polypropylene, polystyrene, polyethylene terephthalate, cellulose esters, or the like. Inasmuch as the method of the invention is especially useful for processing elongated or continuous strips of film with similarly shaped processing elements, the invention 0 will be described in detail in connection with such an operation although it will be understood that the new ethod is equally applicable to the processing of silver halide-sensitized sheets or plates.
In a preferred modification the new web process is employed for developing and fixing a long strip of black and-white photographic film. In carrying out the process a previously exposed strip of silver hailde-sensitized negative film is brought into intimate contact with a processing web and maintained in contact therewith until the negative is substantially completely developed and fixed. The web is then removed from the emulsion layer. The processing web at the time of contact with the silver halide emulsion layer contains all or" the chemical components required to develop the latent image and to clear substantially all of the unexposed silver halide from the emulsion layer. The processing web may be supplied in roll form presoaked in processing solution, in rolls of dry web containing all of the chemical ingredients of the processing solution but no water, or as a dry web containing only the dispersed silver halide precipitating agent. The dry webs are impregnated with water or processing solution, whichever is needed, just prior to use. The silver halide emulsion layer to be processed and the processing web may be brought together and maintained in intimate contact for the required period of time by any suitable means.
A typical device for this purpose is schematically illustrated in the accompanying drawings. Apparatus of the type illustrated may be used to process strips of film or" any desired length according to the new method. One such apparatus has, for example, been employed to process strips of microfilm and motion picture film up to 100 feet or more in length. The apparatus comprises a supporting means, not shown, upon which a film supply spool It), a processing spool 11 and a web supply spool 12 are rotatably mounted. The lower portion of the web supply spool 12 is enclosed by a tank 13. The processing web 14, which is at least as long as the film to be processed, is connected at one end to the core of the web supply spool 12 and at the other end to the core of processing spool 11. The web contemplated in this description of the apparatus is of the type which is supplied dry, containing only dispersed silver precipitating agent in the hydrophilic layer. The bulk of the web lid is initially coiled on the web supply spool 12 so that the hydrophilic surface of the web containing dispersed silver precipitating agent is on the inside. Rollers, not shown, may be mounted below the web supply spool 12 to provide an extended path for the web 14 through the tank 13 filled with processing solution 16. Means, not shown, are provided for rotating the spools l1 and 12 in either direction as desired.
In operation, the processing web 14 is wound from spool 12 onto the processing spool 11. The tank 13 is then filled with processing solution lid. The web 14 is then wound from spool 11 onto spool 12 as shown in FIG. 1 passing over rollers, if provided, and through the processing solution 16 in tank 13 at such a rate that the web absorbs a predetermined amount of processing solution sufficient to develop and fix the film to be processed. When this has been done the direction of rotation of spools 11 and 12. is reversed and the web is rewound onto spool 12 until only one wrap of the soaked processing web remains on spool 11. The end of the film 15 to be processed is then connected to the core of processing spool 11 by any suitable means in such a way that the emulsion side surface of the processing web. The tackiness of the soaked web may be sutlicient to hold the end of the film in contact with the web on the spool 11. Spool ill is then rotated in the direction shown in FIG. 2 of the drawing with the result that the film l5 and soaked processing webl are wound on spool 11 with the exposed emulsion layer of the film in intimate contact with thehydrophilic layer of the processing web. The film and web are allowed to remain in intimate contact on the processing spool until the film is substantially completely developed and fixed. The length of the processing period depends upon many factors known to those skilled in the photographic arts; about 2-10 minutes being sutficient in most cases as will be discussed further below. When processing is complete the film and web are separated by winding them back onto their respective spools Id and 12. In so doing the web 14 picks up fresh processing solution in passing through the tank 3. The rejuvenated web is then ready to process another strip of film.
Apparatus of the type described above may also be employed with dry webs, containing all of the chemical ingredients of the processing solution except water, by merely substituting the required water for the processing solution in tank 13. Similarly the same apparatus with tank 13 empty may be employed with wet webs previously soaked in processing solution.
Alternatively, continuous processing devices may be employed, where the dimensions and rate of film travel while in contact are so adjusted that sufficient processing time is obtained. For instance, the film and web are brought together by means of a pair of wringer rollers and allowed to remain in contact for the required processing time while traveling to a second pair of rollers where the elements are separated.
As will be appreciated by those skilled in the art, proc essing webs such as those described above may tend to deteriorate in time if stored containing highly alkaline processing solution, especially when the hydrophilic layer is composed of gelatin. It has been observed that degradation of such a web on storage reduces its ability to process photographic emulsion layers. This difficulty has been traced to the loss of alkalinity in the web which is probably due to the combination of alkaline material in the processing solution with acidic residues produced during degradation of the hydrophilic layer. Deterioration of the web and loss of alkalinity may be obviated by the use of a separate dry web containing the alkaline reagent normally present in the processing solutions of the invention. Processing of a photographic silver saltsensitized emulsion layer is then accomplished by bringing the dry alkaline web into contact with a web wet with processing solution, minus the usual alkaline inof the film is in contact with the hydrophilicgredient, and the combined web brought into contact with the emulsion layer to be processed. Diffusion of the inactive processing solution from the wet web into the dry alkaline web generates an active processing solution which is capable of developing and fixing the photographic emulsion layer. The dry alkaline webs comprise a suitable hydrophilic layer which may, for example, be composed of gelatin, polyvinyl alcohol, regenerated cellulose such as cellophane and the like. The hydrophilic layer is treated with a solution of one of the amine-sulfur dioxide addition products employed as alkaline materials in the usual processing solutions. The treated alkaline web is then dried and stored until needed. In this way it is possible to provide wet webs containing all of the processing ingredients except the required developer activator and dry webs containing the necessary alkaline ingredient, both webs being stable on storage for extended periods of time.
The processing elements or webs of the present invention comprise a hydrophilic organic colloid layer containing dispersed silver-precipitating agent. The hydrophilic layers may be employed alone if they have sufficient strength to be self-supporting or if desired, they may be coated on suitable film supports. The film supports and any subbing layers should preferably be inert to the chemicals in the processing solution and it is desirable in some cases that such supports be hydrophobic in nature as well. Suitable hydrophilic organic colloids include gelatin, cellophane, polyvinyl alcohol, hydrolyzed cellulose acetate, cellulose ether phthalate, carboxylated rubber, and similar materials. Particularly useful hydrophilic materials are gelatin and a copolymer made up of 80% acrylic acid and ethyl acrylate. It is essential for best results in the operation of the new processing method that the hydrophilic colloid layer be readily separable from the emulsion layer of the film to be processed. The emulsion layer will, of course, be composed of gelatin in most instances. It has been found that processing webs in which the hydrophilic layer is composed of gelatin are especially satisfactory in that the surface of the web adheres well to the gelatin emulsion layer of the photographic film during processing but is also readily separated from the processed film when processing is complete.
Certain finely porous, spongy materials, although not necessarily hydrophilic in the usual sense, can be used to hold the processing solution. One particularly advantageous material is a porous polyvinyl chloride film which has sufficient tensile strength to be used as a self-supporting processing web. Some of the other hydrophilic colloids mentioned earlier, e.g. cellophane and hydrolyzed cellulose acetate, may also be used in some instances without a separate underlying support.
The silver precipitating agents incorporated in the hydrophilic colloid layer of the processing webs may be physical development nuclei or chemical precipitants including (a) heavy metals, especially in colloidal form, and the salts of these metals, (b) salts, the anions of which form a silver salt less soluble than the silver halide of the photographic emulsion to be processed, or (c) non-diffusing polymeric materials with functional groups capable of combining with and insolubilizing silver ion. Suitable silver precipitating agents for use in the invention are disclosed in Rott US. Patent 2,352,014, Yutzy and Yackel US. Patent 2,740,717, and in Yackel et al. United States patent application Serial No. 586,705, filed May 23, 1956, now US. Patent 3,020,155, issued February 6, 1962. More specifically, useful silver precipitating agents include sulfides, selenides, polysulfides, polyselenides, thiourea and its derivatives, mercaptans, stannous halides, silver, gold, platinum, palladium, and mercury, colloidal sulfur, aminoguanidine sulfate, aminoguanidine carbonate, arsenous oxide, sodium stannite, substituted hydrazines, xanthates, and the like. Polyvinyl mercaptoacetate is an example of a non-diifusing polymeric silver precipitant. Heavy metal sulfides such as lead, silver, zinc,
nickel, antimony, cadmium, and bismuth sulfides are useful, particularly the sulfides of lead and zinc alone or in admixture, or complex salts of these with thioacetamide, dithio-oxamide, or dithio-biuret. The heavy metals and the noble metals particularly in colloidal form are especially effective. Other silver precipitating agents will occur to those skilled in the art.
The particular means employed to precipitate silver in the hydrophilic layer will depend on the demands of simplicity, ease of fabrication, compatibility, and the effect on the photographic quality of the light sensitive element to be processed. As indicated, silver precipitating agents may be materials that act as nuclei or will form nuclei which are sites for physical development upon which metallic silver from the soluble silver complexes may be deposited by the action of developing agents. Those silver :recipitants that will form metallic silver directly or form insoluble silver salts may be incorporated in the hydrophilic layer in sufficient quantity to supply stoichiometric amounts for reduction or precipitation of silver ion, rather than in the considerably lower quantities used to promote physical development or catalytic decomposition.
The concentrations of silver precipitants in the hydrophilic layer of the web must at least be sufficient to insure positive and complete removal or" undeveloped silver halide from the light sensitive element to be processed. However, it has been found that a very considerable degree of control of the sensitometric properties of the image in web processed photographic material can be obtained through choice of the silver precipitant and by adjusting its concentration. For example, Carey-Lea silver nuclei incorporated in the hydrophilic layer of the web to give a coverage of 3 mg. of silver nuclei per square foot is sufficient to cause complete removal of substantially all undeveloped silver halidefrom a silver chlorobromide negative material processed by such a web. As this coverage is increased up to mg. of silver nuclei per square foot negative fog is lowered and the processing rate increases. Furthermore, the use of lead sulfide nuclei in a gelatin layer at a coverage of 8 mg. per square foot has been found to result in higher negative contrast when the same photographic material is processed. In turn, increasing the coverage of lead sulfide nuclei. will increase the contrast and speed of the processed negative image, while lowering maximum density. The lead sulfide and carey-Lea silver nuclei are the preferred silver precipitants when used at coverages of 3 to 120 mg. per square foot in the hydrophilic layer of the web.
Although the silver precipitating agents of the present invention are chemically the same as those employed by Rott, Land and others in solvent transfer system of the prior art, they are generally employed in concentrations of a different order of magnitude. Concentrations of from about 3 to 120 milligrams of nucleating agent, e.g. Carey-Lea silver, per square foot of web are used in web processing to obtain rapid and thorough processing of a photographic negative whereas in the solvent transfer systems of the prior art only about 0.5 to 2 milligrams of colloidal nuclei are employed per square foot of receiving sheet.
it is important that the web be composed of a material which will swell and absorb aqueous solutions and that the extent of this absorption be sufficient to accommodate enough of each processing ingredient to obtain substantially complete development and fixation. In general it has been found that processing webs of the type described intended for the processing or" slow or moderate speed silver chlorobromide films. If the amount of silver halide dry web to the moist negative.
'7 per unit area of the negative film is high or if the film contains a silver brornoiodide emulsion, a higher degree of solution absorption in the web may be necessary. An upper practical limit of processing solution absorption would be about 25 grams per square foot.
it is import-ant when it is desired to store webs containing processing solution that any tendency of the webs to exude liquid should be minimized. Exudation may appear as small droplets of liquid growing upon the surface of a soaked web after excess processing solution has been removed with a squeegee. These droplets of the processing solution may make it difficult to achieve intimate contact between the web and the negative to be treated, thus reducing the efiiciency of the process. The otherwise preferred acrylic acid-ethyl acrylate webs have a greater tendency than gelatin to exude processing solution. It has been found, however, that this tendency can be minimized by coating the hydrophilic copolymer on a suitable support at a coverage of about 2 grams per square foot and hardening the copolymer to the point Where it will absorb only 5 to 6 grams of processing solution per square foot, resulting in not more than about 309% swelling of the hydrophilic layer. A suitable hardener is bis(2,3-epoxypropoxyethyl) ether used in amounts between 0.5 and 2.5% based on the weight of the copolymer. 7
When it is desired to store rolls of processing web containing processing solution, care must be taken to prevent oxidation or drying of sections of the web which would cause incomplete development and fixation in use. Therefore, it is necessary that each convolution of web in a roll be in contact over its entire surface with an adjacent convolution since any gaps provide access for air. The sides of the presoalted web roll must be protected against drying out and oxidation during storage, either by soaking the entire roll in an impermeable package or by the use of tight fitting pressure flanges. In addition to the obvious solution to the problem of eliminating gaps in the roll by careful winding of the web under suitable ten sion, it has been found that the use of a duplitized web is advantageous. A duplitized web is one in which both surfaces of a film support, for example, are coated with a hydrophilic layer. Such a web would be prepared for eventual use by soaking both hydrophilic layers in processing solution and then coiling the web upon itself under tension, thus assuring intimate contact between the hydrophilic layer on the outside of each coil and the hydrophilic layer on the inside of the succeeding coil of the web. The two hydrophilic layers can be the same or different. One or both of the layers may contain silver halide precipitating agent and may be employed in the processing of a silver halide emulsion. Alternatively, one or" the hydrophilic layers may be especially constituted to have mechanical properties making it particularly suitable as a cushion for the hydrophilic processing layer.
The processing webs of the present invention may also be prepared and stored in a dry condition. Webs of this type are prepared by soaking in a processing solution in the usual way and then drying the web to remove the free water. The web may then be rolled or not as desired and stored in a convenient manner. Alternatively the hydrophilic layer may be coiled with the processing solutions incorporated, and then dried. Dry webs of this type containing all of the chemical ingredients of the processing solution may be readied for use by replacement of the necessary water in a variety of ways. For example, the moisture may be replaced by steaming the web prior to use or the web may be dipped in water briefly and the excess removed with a squeegee. A third method is to dip the negative to be processed in water, remove the excess with a squeegee or soft sponge and then apply the It has been discovered, surprisingly enough, that dry webs containing the chemical processing ingredients may be rendered suitable for use in the method of the invention by replacing less than one-half the amount of water originally present in the processing solution used in the preparation of the web. Webs containin the reduced amounts of water have been found to yield processed negatives sensitometrically equivalent to those processed with webs used directly after soaking, and the reduced amount of water present providcs a processed negative which is substantially drier than those obtained in the usual way. On the other hand a web soaked in a double strength modification of a preferred processing solution, and permitted to absorb the same amount or" the processing solution ingredients (eX- ept Water) as when soaked in the normal solution, gives poor processing of the negative.
In addition to the presoaked webs and dry webs containing processing chemicals which are described above, the invention also includes webs composed of hydrophilic colloid layers containing only dispersed silver precipitating agent. Webs of this type are soaked in processing solution immediately prior to use.
Tie processing solutions of the present invention comprise one or more silver halide developing agents, a silver halide solvent, an amine-sulfur dioxide addition product and water. Certain other ingredients may also be prescut, for example, where foam on the processing solution is not a problem, it has been found that the addition of certain surface active agents to the processing solution improves the quality and effective sensitometric speed of the negatives obtained. Further, the addition of small amounts of potassium iodide to the processing solution modifies the deposition of silver in the web. In some instances small amounts or" potassium iodide have been found beneficial in eliminating a mirror-like coating which is formed on the surface of the negative. The shape of the characteristic curve or" the processed photographic element may be varied not only by adjusting the silver coverage and hardness of the negative but also by adjusting the concentration of the ingredients of the processing solution and the character and concentration of the silver precipitating agent in the web.
The silver halide developing agents which may be employed in the processing solutions include methyl-paminophenol sulfate hydroquinone, chlorhydroquinone, diaminophenols, e.g. 2,4-diaminophenol and 3,4-diaminophenol hydrochloride, glycine, l-phenyl-S-pyrazolidone and its derivatives, triaminophenols, including 2,4,6-triaminophenol, catechol, pyrogallol, gallic acid, paraphenylene diamines, ene-diols, such as ascorbic acid, and combinations of these developing agents. Especially useful developing compositions comprise mixtures of monomethy-p-aminophenol sulfate and hydroquinone; l-phenyl-3-pyrazolidone and hydroquinone; and especially 4,4- dimethyl-l-phenyl-Z-pyrazolidone and hydroquinone.
The processing solution must have certain very definite characteristics which are not common to conventional rnonobaths used in simultaneous development and fixation of silver halide emulsion layers. For example, the processing solution must be capable of absorption by the hydrophilic colloid layers described above to provide complete processing and therefore, must have a relatively low salt content. The low salt content is also necessary to prevent crystallization on the processed negative inasmuch as the usual final Washing operation may in some cases be eliminated in the new process. The developing capability of the processing solution must also be relatively high both as to capacity and rate since development should be essentially complete before fixation occurs. Further, inasmuch as the web process does not provide a reservoir of silver halide solvent as is the case with conventional monobath'processing, the concentration of silver halide solvent is generally substantially less than that present in such monobaths. For example, monobaths for processing photographic materials em loy sodium thiosulfate pentahydrate in concentrations of 50 to 200 grams per liter while developers for the web process use only 2 to 25 grams of sodium thiosulfate pentahydrate per liter.
Further, since all the products of development are contained at the sites of development, and cannot diffuse into a surrounding bath, the processing solution must contain highly efficient agents that will overcome the effect of restraining products produced by development. In particular, most photographic developers contain a pre servative, such as sodium sulfite which will react With the oxidized developing agent formed in the development process or by aerial oxidation, thus removing these oxidation products and preventing them from causing development restraint or otherwise affecting the development process. In addition the development reaction is acid forming and it is therefore necessary to employ efiicient buffering alkalis in the developer solution that will react with the acid formed and prevent large changes in pH that would cause signficant changes in the development process.
For the purposes of this invention, it was found that the amine-sulfur dioxide addition products may be added to processing solutions to provide efficient preservative and buffering action. The amine-sulfur dioxide addition products are prepared by reacting a suitable amine with sulfur dioxide gas. Amines suitable for this preparation include primary, secondary, and tertiary amines such as Z-aminoethanol, Z-rnethylaminoethanol, 2-dirnethylaminoethanol, Z-ethylaminoethanol, Z-diethylaminoethanol, 2,2,2"-nitrilotriethanol, 2-aminoethylaminoethanol, 2,2-iminodiethanol, 5-diethylamino-Z-pentanol, Z-amino- 2-methyl-l-propanol, morpholine, and piperidine, among others. For the present invention the preferred aminesulfur-dioxide addition product is prepared in the following manner. Sulfur dioxide gas is slowly bubbled through one mole of the preferred amine, 2,2-iminodiethanol, with adequate stirring until it adsorbs the equivalent of 0.25 mole of sulfur dioxide. The resulting 2,2'-iminoethanol-sulfur dioxide addition product contains the equivalent of 13 percent sulfur dioxide by weight, or mole percent. When this amine-sulfur dioxide product is incorporated in typical processing solutions of the present invention a pH from 9.0-9.5 is obtained.
The preferred amine-sulfur dioxide addition products contain about 20 mole percent sulfur dioxide, but depending on the requirements of pH, buffering capacity and preservative action the percentage of sulfur dioxide in the addition products may be varied from about 5 to 33 mole percent. Thus through proper choice of starting amine and the amount of reaction with sulfur dioxide, amine-sulfur dioxide addition products may be prepared that, when added to Web processing solutions, will produce a pH from about 7.0 to about 11.5.
The preferred product 2,2-iminodiethanol-sulfur dioxide addition product (20 mole percent sulfur dioxide) has many particular advantages when used in the new web processing solutions, which are demonstrated to a somewhat lesser extent by other amine-sulfur dioxide addition products in one respect or another. A number of amine-sulfur-dioxide products have volatile components which are thought to cause fogging of photographic emulsions that may be stored in the presence of Web processing solutions prior to processing. Vapor pressure attributable to the 2,2-iminodiethanol addition product is relatively low and practically no fog is produced on films stored in the presence of this product.
The amine-sulfur dioxide addition products have been found to have an effect upon the pick-up or absorption of processing solution by webs. In general, sulfur dioxide addition products prepared from primary amines appear to cause disproportionate swelling of both soft and hard gelatin coatings but have no adverse effect on hydrophilic coatings of the acrylic acid-ethylacrylate copolymer. Products prepared from secondary and tertiary amines have not been found to soften gelatin coatings in any appreciable degree. This is particularly true of the it) 2-,2'-iminodiethanol-sulfur dioxide addition product and Webs presoaked in processing solutions containing this product may be stored for long periods of time without appreciable degradation of the hydrophilic colloid layer.
The pH of the processing solution also has a considerable eifect upon the degree of absorption obtained with acrylic acid-ethyl acrylate copolymer hydrophilic layers although its effect is minor with gelatin layers. In general, satisfactory results are achieved with processing solutions having a pH in the range from about 8.7 to about 9.5. The preferred 2,2-iminodiethanol sulfur dioxide addition product is used in developers to produce solutions ranging in pH from 9.0 to 9.5 which is within the range that produces the desired degree of absorption. In addition these moderate pH processing solutions have sufiicient activity to give the desired complete processing. This is surprising since the pH range is well below the pH at which conventional monobaths operate. Still further the moderate pl-I solutions containing this aminesulfur-dioxide addition product have considerably less tendency to cause degradation of hydrophilic layers of stored presoaked webs than is the case with higher pH solutions. The moderate pH and absence of active volatile components of solutions containing this amine-sulfur dioxide addition product results in a processing solution of lower toxicity than that associated with higher pH developers or those containing amine-sulfur dioxide addition products of higher volatility.
The web process can be operated by the use of modifications of conventional developers or monobaths, however, but at the expense of one or more of the advantages listed herein. For example, a conventional monobath containing a preservative such as sodium sulfite and a buffering alkali such as sodium carbonate may be used in a Web. However, due to high salt concentration, insufficient amounts of such a solution would be absorbed in acrylic-acid ethyl acrylate copolymer hydrophilic layers to give complete processing and solution will exude from the web on storage. Webs employing a gelatin layer will more readily absorb such a monobath, but are likely to deteriorate on storage both because of the action .of the alkali on the gelatin and the tendency for water to evaporate from the web. In contrast, solutions of similar pho tographic capacity employing the preferred 2,2-iminodiethanol sulfur dioxide addition product despite generally lower pH, are readily absorbed in both gelatin and acrylic acid-ethyl acrylate copolymer layers, and will not subsequently be exuded from such layer, or cause deterioration of the layer on storage. The humectant-like properties of the amine-sulfur dioxide addition product also inhibits the evaporation of Water from the soaked Web.
It is also possible to prepare monobaths that include a preservative such as sodium sulfite and an amine, including those amines which are uesd to prepare aminesulfur dioxide addition products, as an alkali. These are more readily absorbed in hydrophilic layers than those solutions containing inorganic alkali buffers. However, the higher salt concentration that results from the use of sodium sulfite in sufficient quantity to provide adequate preservative action still makes such solutions inferior to those containing amine-sulfur dioxide addition products. In addition the photographic results produced by developers containing amine-sulfur dioxide addition products and the stability of such solutions are often better than those of similar developers in which unreacted amine and sodium sulfite are employed.
The concentration of amine-sulfur dioxide addition product affects the degree of absorption of processing solution by the webs. In general, an increase in the concen tration of the addition product results in a decrease in absorption by the web. This is particularly true with the acrylic acid-ethyl acrylate copolymer hydrophilic layers where a variation in the concentration of the amine addition product from 50 to 500 grams per liter of processing solution results in a decrease in absorption of from 16 to 4 grams per square foot. Absorption by gelatin webs on the other hand, varies only from 5.5 to 3.2 grams per square foot under similar conditions. The polyvinyl alcohol webs are also quite sensitive to the concentration in the processing solution of amine-sulfur dioxide addition product, the absorption of solution dropping to 2 grams per square foot at a concentration of 250 grams of amine per liter. Large concentrations of the amine-sulfur dioxide addition product increase the viscosity of the processing solution which is generally undesirable. The speed and fog of the processed photographic element also increase with the concentration of amine-sulfur dioxide addition product. Taking all of the above into consideration, it has been found that a concentration of the aminesulfur dioxide addition product from about 35 to about 200 grams per liter, depending on the choice of the amine and the molar proportion of sulfur dioxide, have been found to provide sutficient preservative action, pH, total alkalinity, and satisfactory sensitometric properties under varying conditions of use. The amine sulfur dioxide addition compounds are uniquely useful in the web process. Higher effective concentration of the developer is possible, the presoaked webs are more stable, and development is efiective at a lower pH.
Although any of the well known silver halide solvents e.g. alkali thiocyauates, alkali selenocyanates, thioglycerol, aminoethanethiols, ,6,,B'-dithiasuberic acid, etc., may be employed as a fixing agent in the processing solution of the present invention, the preferred solvent is hypo, sodium thiosulfate pentahydrate. The concentration of this reagent in the processing solution may range from 2 to about 25 grams per liter with advantage. In most cases, for example, it has been found that about 8 grams per liter of sodium thiosulfate pentahydrate provides satisfactory clearing of undeveloped silver halide with acrylic acid-ethyl acrylate copolymer webs whereas about 6 grams per liter is sufhcient with gelatin webs.
A particularly useful processing solution of the present invention has the following composition:
Water to make 1.0 liter.
The process is carried out at ambient or slightly elevated temperatures. For example, up to about 85 F, the temperature not being particularly critical. The rate of negative image development with processing solutions of the type described above is rapid, it having been observed that a significant degree of development takes place within 10 seconds and that maximum contrast is usually achieved after about seconds. Development is essentially complete within one minute. Clearing of the undeveloped silver halide from the silver halide emulsion is essentially complete at the end of 4 minutes in most instances. Therefore, processing times of from about 4 to 10 minutes are generally sutiicient. However, since the processing reaction goes to completion, no harm is done in leaving the negative in contact with the web for even a period of hours, providing that loss of moisture which might cause the two sheets to become cemented together, does not occur.
The method and compositions of the present invention are generally applicable to the processing of photographic emulsions of the developing-out type. 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 emulsions are formulated according to known procedures and may include any of the usual addenda such as sensitizers, antifoggants, hardeners and the like.
1.2 The method and compositions of the invention can also be employed to process silver salt-sensitized emulsion layers containing incorporated developing agent. In this embodiment the silver halide developing agent is omitted from the processing solution since his already present in the emulsion layer, all other steps of the process being carried out as with the usual developing agent-containing processing solutions and webs.
The invention will now be described in greater detail in the followin examples which are chosen for purposes of illustration and are not intended to limit the scope of the invention.
Example 1 A processing web was prepared in the following manner: A cellulose acetate film base was placed in a hydrolyzing bath (sodium hydroxide aqueous alcohol solution) for one hour and tncn washed and dried. This treatment iydrolyzed enough of the surface of the film base so that it would pick up sufiicient solution for web processing. Nuclei were incorporated in the hydrolyzed acetate by the following procedure:
The hydrolyzed sample was soaked for 3 minutes in a 0.1% gold chloride solution followed by a 3-minute soak in a 0.2% solution of monomethyl-p-aminophenol sulfate. This formed metallic gold nuclei in the hydrolyzed acetate. The sample was then washed for 5 minutes in water.
Processing chemicals were introduced to the Web by soaking it'for 5 minutes in a solution comprising:
Grams 1-henyl-3-pyrazolidone 1.0
ydroquinone 10.0 Z-dirnethylaminoethanolsulfurdioxide (20 mol percent SO 174.0
Sodium thiosulfate pentahydrate 11.0
Potassium bromide 2.0
Water to make 1.0 liter.
he web was squeegeed ofiafter soaking. A silver chlorobromide negative material was suitably exposed and rolled in contact with the soaked web and allowed to remain for 10 minutes. Whenthe two were peeled apart, full development of the negative had occurred and the unexposed areas were cleared of silver halide.
Example 2 Grams 4,4-d1methyl-1-phenyl-3-pyrazolidone 1.0 Hydroquinone 10.0 2,2-iminodiethanol-SO addition product (20 mol percent 190.0 2,2'-iminodiethanol 50.0 Sodium thiosulfate, p-entahydrate 8.0
Water to make 1.0 liter.
The sheet was then squeegeed off and rolled in contact with a suitably exposed negative emulsion. After 10 minutes, the two were separated. A fully developed negative image had formed on the exposed film while the unexposed areas were cleared of residualsilver halide.
Example 3 On a cellulose acetate support was coated a layer comprising 2 grams of gelatin and 8 mgm. Carey-Lea silver per souare foot. A hardening agent was included at a concentration sufficient to limit the absorption to 5 grams 13 per square foot when soaked for 3 minutes in a solution consisting of:
2,4,6-triaminophenol grams 6 2,4-diaminophenl hydrochloride do 6 Triethanolamine-SO addition product (20 mol percent S0 rnl 100 Sodium thiosulfate grams 3 Carboxymethyl cellulose (2% solution) ml 100 Water to make 1 liter.
After soaking, the web was drained and squeegeed and then rolled in contact with a suitably exposed silver chlorobromide negative emulsion. The negative image was developed and residual silver halide cleared from this negative emulsion during the minutes it was left in contact with the web.
Example 4 A gelatin web containing Carey-Lea silver nuclei similar to that already described in Example 3, was soaked for 3 minutes in a solution comprising:
2,4,6-triaminophenol "grams" l2 Triethanolamine-SO addition product mol percent S0 ml 200 Sodium thiosulfate pentahydrate grains 2 Carboxymethyl cellulose (2% solution) m1 200 Example 5 A web material was prepared in which the hydrophilic layer consisted of a copolymer of acrylic acid and ethyl acrylae in the proportions of 80:20. The copolymer was provided in a water solution containing 8.3 percent solids and 12 percent isopropanol.
At 60 C. a mixture was made comprising:
Copolymer solution "grams" 9520 Isopropyl alcohol ccs 474 Distilled water ccs 2753 Carey-Lea silver (as a 5% gelatin solution containing 0.485 gram silver per gram dry gelatin) "grams" 3136 Bis(2,3-epoxypr0poxyethyl)ether ccs 4.1 4-chloro-3,5-xylenol, 3% methanol solution ccs 24 Saponin (15% solution) ccs 80 The coating was made on a polyester support by the usual emulsion coating techniques. The resultant coating had 1.44 grams solids and 108 mg. silver/ft? After the web coating had hardened, a piece was soaked for 3 minutes in a developer comprising:
Grams Z-dimethylaminoethanol 71 Z-dimethylaminoethanol-SO addition product (31.6
percent S0 .96 4,4-dimethyll-phenyl-3-pyrazolidone .96 Hydroquinone 9.6 Potassium bromide 1.9 Hypo 10.55
Water to make 1 liter.
14 Example 6 A web containing silver sulfide nuclei was made as follows:
A solution comprising:
Silver nitrate, 1 Normal 8.8 Ammonium hydroxide sufficient to convert the silver nitrate to the soluble silver ammonium complex 200 Distilled water.
was mixed rapidly with good stirring to the following solution which had just been heated to 60 C.:
Copolymer solution, as in Example 5 ccs 1485 Distilled water ccs 306 Sodium sulfide, 1 Normal ccs 8.8
After stirring for 5 minutes, there were added 15% saponin solution ccs l0 Bis(2,3-epoxypropoxyethyl)ether cc 0.6
The solution was coated in the same manner as the previous example. The coating contained 11.7 mg. silver as silver sulfide per ft.
After hardening, the web was soaked in the processing solution of Example 5 for 3 minutes at 70 F. After soaking, the web was drained and squeegeed and then rolled in contact with a suitably exposed silver chlorobromide negative emulsion. The negative image was de veloped and the residual silver halide cleared from this negative emulsion during the 10 minutes it. was left in contact with this web.
Example 7 A polyvinyl alcohol coated web was made as follows: A solution comprising 5% Elvanol 71-30 ccs 1500 Sodium sulfide, 1 Normal ccs 30 A polyvinyl alcohol available from E. I. du Pont de Nemours and Company.
was mixed rapidly with good stirring with a solution comprising 5% Elvanol 71-30 ccs 1500 Silver nitrate, 1 Normal ccs 30 After stirring, the following were added:
1% borax (pH 5.5) ccs 150 15% saponin ccs 30 The Elvanol was put in solution by heating to C., but the mixture was cooled to 40 C. for coating. Gelation of the liquid coating was brought about by fuming with ammonia, after which the coating was dried. As coated on a polystyrene support, the hydrophilic layer contained 1.65 grams of solids and 32 milligrams of silver as silver sulfide per square foot.
The web was soaked in the processing solution of Example 5 for 3 minutes at 40 (1., after which it was drained, squeegeed, and rolled in contact with a suitably exposed silver chlorobromide negative emulsion. The negative image was developed and the residual silver halide cleared from this negative emulsion during the 10 minutes it was left in contact with the web at 70 F.
Example 8 A web comprising the gelatin hydrophilic layer of Example 3 but coated on a polyester support was soaked for 3 minutes at 70 F. in a processing solution comprismg:
Grams 2,2'-1minodiethanol-SO addition product (13.0%
Water to make 1 liter.
Example 9 A web similar to that of Example 8 but containing 4 grams of gelatin per square foot was soaked for minutes at 85 F, to give an absorption of 23 grams per square foot, in a processing solution comprising:
Grams 2,2-iminodiethanol-SO addition product (13% S0 200 Hydroquinone 40 4,4-dimethyl-l-phenyl-3-pyrazolidone 2 Monomethyl-p-aminophenol sulfate 6 Sodium thiosulfate pentahydrate 14 Potassium iodide 0.2
Water to make 1 liter.
At 70 F., the soaked web was wrung in contact with an exposed sheet of a very high-speed, moderate-grain, silver bromo-iodide negative film. On separation after 30 minutes, the negative was found to be developed and fixed. The sensitometric curve closely matched that obtained by processing the same film for 12 minutes in the conventional Kodak D-76 Developer, but was 0.2 log E faster (Exposure E in meter-candle seconds).
Example A solution (A) containing gelatin and a processing solution was made in the following proportions:
Developer ml 400 N-methyl-p-aminophenol sulfate grarns 3.1 Sodium sulfite do 45.0 Hydroquinone do 12.0 Sodium carbonate, desiccated do 67.5 Potassium bromide do 1.9 Water to make 1 liter.
% gelatin ml 125 Sodium thiosulfate pentahydrate grams 60 The solution was mixed and held at 40 C. A solution (B) containing nuclei for physical development was prepared by mixing solutions of zinc nitrate and sodium sulfide in the presence of gelatin so that the final cornposition was 0.1 N zinc sulfide and 2.5% gelatin.
A mixture comprised of:
Solution A ccs 100 Solution B ccs 100 Potassium bromide gram 0.4
As in Example 8, the web was soaked in the processing solution, but after squeegeeing, was dried with a hair drier.
A slow silver chlorobromide negative film was exposed, immersed in water for 30 seconds, squeegeed, and wrung in contact with the dry processing sheet. On separation after 10 minutes, a developed and fixed negative image was obtained.
Example 1 2 A nondiifusing polymeric silver precipitant was prepared by adding 5 grams of polyvinyl alcohol (Du Pont Elvanol 7130), with stirring, to ml. of mercaptoacetic acid. The swollen mixture was warmed on the steam bath and treated with 0.5 ml. of concentrated sulfuric acid. After one-half hour, the solution was cooled and diluted with 4-5 ml. of dioxane. This solution of polyvinyl mercapto acetate was coated on hydrolyzed acetate film base, dried, washed in water to remove impurities, and redried. A suitably-exposed, fine-grain silver bromoiodide photographic film was bathed in a developer solution comprising:
Grams N-methyl-p-aminophenol sulfate 2.5 Hydroquinone 4.5 Sodium sulfite (desiccated) 25.0 Sodium carbonate monohydrate 40.0 Sodium thiosulfate pentahydrate 10.0 Potassium bromide 1.0
Water to make 1 liter.
The photographic emulsion was then placed in intimate contact with the polyvinyl mercapto acetate coating and allowed to remain in contact for 4 minutes, after which time the two were separated. An image was formed in the exposed area and unexposed silver halide was removed from the emulsion and deposited in the polyvinyl mercapto acetate layer.
Alternately, the polyvinyl mercapto acetate coating may be overcoated with a gelatin layer and this layer soaked in the above developer solution prior to placing it in contact with the exposed film. Furthermore, the polyvinyl mercapto acetate may be dispersed in gelatin and coated on a suitable support to make a processing web.
It has been found that the processing webs of the present invention such as those described in detail in the foreging examples may be regenerated for reuse by treatment with fresh processing solution. Webs in which the hydrophilic layer is composed of gelatin or a copolyrner of acrylic acid and ethyl acrylate have, for example, been regenerated and reused for processing additional silver halide emulsion layers up to 20 times or more with satisfactory results. The technique of regenerating the Webs of the invention will be illustrated by the following example.
Example 13 A web comprising a hydrophilic layer composed of a copolyrner of acrylic acid and ethyl acrylate in the proportions of :20 was soaked for 4 minutes in the processing solution of Example 2, squeegeed and brought into intimate contact with a strip of silver halide sensitized negative film. Smooth even contact was established by pressing the web and the film between steel rollers. The resulting web-film sandwich was stored in the dark for 10 minutes and then the web and film were separated yielding a fixed negative image in the film and the usual positive image in the web. The web was then resoaked in freshprocessing solution and the process repeated with a similar strip of previously unprocessed film. The second strip of photographic film was satisfactorily developed and fixed. The same web was then employed repeatedly in the processing of additional strips of film, being rejuvenated by treatment with processing solution between each successive use. After 20 such processing cycles with the same web, the web had become quite dark in color but was still capable of achieving a satisfactory negative image in a strip of film when resoaked in processing solution. Sensitometric comparison of the processed negatives showed a slight loss in speed and contrast but no loss in fixation after 20 uses of the web. A similar series of tests was con ducted with a processing web having a hydrophilic layer composed of gelatin. This Web also achieved satisfactory development and fixation after as many as 20 processing cycles.
The method and compositions of the present invention are useful in a great variety of applications in the field of photography as will be readily apparent to those skilled in the art. The invention provides a rapid and convenient method for processing a wide variety of photographic elements and is especially useful for the development and fixation of long strips of film such as motion picture film and microfilm and in applications where speed of process- 1? ing or the elimination of bulky equipment and processing baths is required, or where water or processing chemicals are not available. The specific modificationse of the invention described in the detailed examples above are illustrative only and are not to be construed as limiting the scope of the invention as set forth in the accompanying claims.
1. A method of processing a silver halide emulsion layer containing a latent photographic image to form a developed and fixed silver image in said emulsion layer which comprises (A) intimately contacting in superposed relation an exposed silver halide emulsion layer with a reusable water-permeable hydrophilic organic colloid processing element separable from said emulsion layer and having dispersed therein a silver precipitating agent, said processing element containing an amount of processing solution suflicient to develop said exposed silver halide to metallic silver and to dissolve substantially all undeveloped silver halide from said exposed emulsion layer and not more than the amount of said solution which said processing element is capable of absorbing without exudation of liquid that makes it difiicult to achieve intimate contact between the said exposed silver halide emulsion layer and the said processing element, said processing solution containing at least one (a) silver halide developing agent, (b) aliphatic hydroxyamine sulfur dioxide addition product and silver halide fixing agent, and (B) maintaining said processing element in intimate contact with said emulsion layer until development of said latent image is substantially complete and substantially all of the undeveloped silver halide has a been cleared from said emulsion layer and precipitated in said processing element, and (C) separating said emulsion layer containing the resulting developed and fixed silver image from the processing element.
2. A method of processing a silver halide emulsion layer containing a latent photographic image to form a developed and fixed silver image in said emulsion layer which comprises (A) intimately contacting in superposed relation an exposed silver halide emulsion layer with a reusable water-permeable hydrophilic organic colloid processing element separable from said emulsion layer and having dispersed therein a silver. precipiating agent, said processing element containing at least about 4.5 grams of processing solution per square foot but not more than the amount of said solution which said processing element is capable of absorbing without exudation of liquid that makes it difiicult to achieve intimate contact between the said exposed silver halide emulsion layer and said processing element, said processing solution having a pH in the range from about 7.0 to 11.5 and comprising:
Water to make 1 liter.
and (B) maintaining said processing element in intimate contact with said emulsion layer'until development of said latent image is substantially complete and substantially all of the underdevelopedsilver halide has been cleared from said emulsion layer and precipitated in said processing element, and (C) separating said emulsion layer containing the resulting developed and fixed silver image from the processing element.
3. The method of claim 2 in which the hydrophilic organic colloid of the processing element is gelatin.
4. The method of claim 2 in which the hydrophilic organic colloid of the processing element is an acrylic acidethyl acrylate copolymer.
5. A method of processing a silver halide emulsion layer containing a latent photographic image to form a developed and; fixed silver image in said emulsionflayer which comprises (A) intimately contacting in superposed relation an exposed silver halide emulsion layer with'a reusable water-permeable hydrophilic organic colloid processing element separable from said emulsion layer and having dispersed therein a silver precipitating agent, said processing element containing at least about 4.5 grams of processing solution per square foot but not more than the amount of said solution which said processing element is capable of absorbing without exudation of liquid that makes it difiicult to achieve intimate contact between the said exposed silver halide emulsion layer and said processing element, said processing solution having a pH in the range of about 9.0-9.5 and comprising:
2,2'-iminodiethanol-sulfur dioxide addition product (20 mole Water to make liter.
and (B) maintaining said processing element in intimate contact with said emulsion layer until development of said latent image is substantially complete and substantially all of the undeveloped silve halide has been cleared from said emulsion layer and precipiated in said process ing element, and (C) separating said emulsion layer containing the resulting developed and fixed silv-er image from the processing element.
6. The method of claim 5 in which the hydrophilic organic colloid of the processing element is gelatin.
7. The method of claim 5 in which the hydrophilic organic colloid of the processing element in an acrylic acid-ethyl acrylate copolymer.
8. A method of processing an exposed silver halide emulsion layer having silver halide developing agent incorporated therein which comprises (A) intimately contacting in superposed relation said exposed silver halide emulsion layer with a resuable Water-permeable hydrophilic organic colloid processing element separable from said emulsion layer and having dispersed therein a silver precipitating agent, said processing element containing at least about 4.5 grams of processing solution per square foot but not more than the amount of said solution which said processing element is capable of absorbing without exudation of liquid that makes it difficult to achieve intimate contact between the said exposed silver halide emulsion layer and said processing element said processing solution having a pH in the range from about 7.0 to 11.5 and comprising:
a Grams Aliphatic hydroxyamine-sulfur dioxide addition product 35-200 Sodium thiosulfate pentahydrate 2-25 Water to make 1 liter.
layer containing the resulting developed and fixed silver image from the processing element.
9. A processing solution having a low salt content and a pH in the range from about 8.7 to about 9.5, said solution being adapted for use in conjunction with a waterperrneable hydrophilic organic colloid processing element containing dispensed silver halide precipitating agent in the development and fixation of a silver salt-sensitized photographic emulsion layer, said solution comprising:
, Grams Silver halide developing agent 5-40 Aliphatic hydroxyamine-sulfur dioxide addition product 35-200 Sodium thiosul'fate penthahydrate Water to make 1 liter.
p 10. A processing solution having a low salt content and a pH in the range from about 8 .7 to about 9 .5, said solution being adapted for use in conjunction with a Waterpermeable hydrophilic organiccolloid processing element containing dispersed silver halide precipitating agent, in the development and fixation of a silver salt-sensitized photographic emulsion layer, said solution comprising:
2,2'-iminodiethanol-sulfur dioxide addition product (20 mole percent S About 190 grams. Hydroquinone About 11-12 grams. 4,4-dimeth l-1-phenyl-3- pyrazolidone About 1 grams. Sodium thiosulfate, desiccated About 5-6 grams.
Water to make 1 liter.
11. A method of processing a silver halide emulsion layer containing a latent photographic image in order to form a developed and fixed silver image in said emulsion layer which comprises the steps;
(a) intimately contacting in superposed relation said exposed silver halide emulsion layer with a first reusable water-permeable hydrophilic organic colloid processing element having a silver precipitating agent dispersed therein and containing at least about 4.5 grams of aqueous processing solution per square foot, said processing solution comprising about 5-40 grams of a silver halide developing agent andabout 2-25 grams of sodium thiosulfate pentahydrate per liter,
(b) intimately contacting in superposed relation said first processing element while it is in contact With said emulsion layer with a second reusable waterpermeable hydrophilic organic colloid processing element containing an aliphatic hydroxyamine-sulfur dioxide addition product in an amount sufiicient, when dissolved in the processing solution of said first processing element, to yield a concentration of said addition product in said processing solution in the range from about 35-200 grams per liter and suflicient to bring the pH of said solution within the range from about 7.0-1l.5,
(c) maintaining said first processing element in intimate contact in superposed relation with said emulsionlayer on one side and with the said second processing element on the other side until development of said latent image is substantially complete and substantially all of the undeveloped silver halide has been cleared from said emulsion layer and precipitated in said first processing element, and g (d) separating said emulsion layer containing the resulting developed and fixed silver image from the said first processing element. 7 p
12. A photographic process in which silver halide emulsion'layers containing latent images are converted to visible fixed silver images in said layers comprising the 5 steps:
(1) intimately contacting in superposed relation said 20 exposed silver halide emulsion layer with a waterpermeable hydrophilic organic colloid processing element having a silver precipitating agent dispersed therein and containing at least about 4.5 grams of aqueous processing solution per square foot, said processing solution having a pH in the nange of from about 7 to about 11.4 and comprising about 5-40 grams of a silver halide developing agent, about 35-200 grams of an aliphatic hydroxyamine-sulfur dioxide addition product, and. from 2-25 .grams of sodium thiosulfate pentahydrate per liter of solution,
(2) maintaining said processing element in intimate contact with said emulsion layer until development of said latent image is substantially completeand substantially all of the undeveloped silver halide has been cleared from said emulsion layer and precipitated in said processing element, then (3) separating said emulsion layer containing the resulting developed, and fixed silver image from said used processing element, and
(4) reusing said used processing element to process more. unprocessed photographic silver halide emulsion layers according to steps (1), (2) and (3) after regenerating said element by replacing in it the processing solution used in steps (1), (2) and (3) by contacting said element with a supply of said processing solution so that the regenerated element contains at least 4.5 grams of processing solution per square foot.
Reierences Cited by the Examiner UNITED STATES PATENTS H Hochstetter 6-29 1,207,042 12/16 2,197,016 4/40 Wood 96-66 2,197,017 4/40 Wood 96-66 2,306,923 12/42 Wood 96-66 2,343,326 4/44 Reckmeyer et al. 9,6-66 2,662,822 12/53 Land 96-29 2,692,830 10/54 Land 96-29 2,834,676 5/58, Stanley 96-66 2,882,151 4/59 Yutzy et al. 96-29 3,017,270 I/ 62 Tregillus et al. 96-29 FOREIGN PATENTS 9,248 5/05 Great Britain. 571,389 8/45 Great Britain. 486,056 8/52 Canada. 713,163 8/54 Great Britain.
7 OTHER REFERENCES Photo Methods for Industry, February 1959, pp. 32- 35, 72 and 73.
NORMAN :FORQHIN, Primary Examiner. PHILIP E. MANGAN, ABRAHAM HlWINKELSTEIN,
MILTON STERMAN, Examiner IINITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,179,517 April 20, 1965 Leonard W Tr egillus et al,
ied that error appears in the above numbered pat- It is hereby certif said Letters Patent should read as ent requiring correction and that the corrected below.
line 61, for "underdeveloped" read line 24, for "silve" read same column 18,
undeveloped column 18, silver line 32, for "in" read is line 67, for "dispensed" read dispersed Signed and sealed this 12th day of April 1966.
( L) Attest:
ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER- Commissioner of Patents