Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C8/00—Diffusion transfer processes or agents therefor; Photosensitive materials for such processes
  • G03C8/02—Photosensitive materials characterised by the image-forming section
  • G03C8/04—Photosensitive materials characterised by the image-forming section the substances transferred by diffusion consisting of inorganic or organo-metallic compounds derived from photosensitive noble metals
  • G03C8/06—Silver salt diffusion transfer
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
  • G03C8/00—Diffusion transfer processes or agents therefor; Photosensitive materials for such processes
  • G03C8/24—Photosensitive materials characterised by the image-receiving section
  • G03C8/243—Toners for the silver image

Definitions

• This invention relates to the silver halide diffusion transfer process of photography and more particularly to methods for increasing the speed of the process and density of reproductions obtained thereby.
• an exposed emulsion layer is developed in the presence of a silver halide solvent, the emulsion layer being for at least a portion, or for the whole of the development period in effective contact with a receiving sheet, the surface of which generally carries a quantity of a silver precipitant which may comprise either physical development nuclei such as colloidal silver or silver sulfide or a chemical precipitant for silver ions, such as zinc sulfide, Development of the emulsion layer proceeds and is followed immediately by complexing of the residual unexposed silver halide with a silver halide solvent also present in the developer composition, and imagewise diffusion of the resulting silver complex to the receiving sheet where the silver precipitant causes the formation of an argental (of or containing silver) image.
• a silver precipitant which may comprise either physical development nuclei such as colloidal silver or silver sulfide or a chemical precipitant for silver ions, such as zinc sulfide
• the tone of they argental image is characteristically warm brown. This is true even if tonemodifying compounds such as the mercaptotetrazoles are employed in the emulsion, the developer or both. Accordingly, when the quaternary salt compounds and certain tone modifying compounds described hereinafter are present at the time the argental image is being formed in the receiving sheet, a profound improvement of the image tone is obtained, i.e. shift in color of the argental image from brown to black, and this effect is obtainable even when carrying out the diffusion transfer processes with stable alkaline developer compositions of pH of the order of about 10 to 10.4. This degree of improvement in image tone cannot be obtained in such solutions by use of the quaternary salt alone in any concentration or by use of the tone'modifying compound alone in any concentration.
• the objects of the invention therefore include providing means for increasing the effective speed ofdiffusion transfer processes, means for improving the tone of the prints obtained in the diffusion transfer processes and means for carrying out the diffusion transfer processes at moderate pH.
• Other objects of our invention will be: come apparent from the following description thereof.
• the onium compounds of the invention which are used in the diffusion transfer processes are quaternary ammonium and ternary sulfonium compounds, the onium radical of which has attached to it a chain containing at least 7 atoms such as carbon atoms, carbon atoms and oxygen atoms, etc. Included among the onium com pounds are the following representative groups of compounds:
• R and R represent alkyl groups, e.g., methyl, cat-boxymethyl, ethyl, propyl, butyl, etc., 'or aralkyl group's, e.g., benzyl,
• R represents an alkyl group of at least 7 atoms, e.g., heptyl, nonyl, decyl, dodecyl, tetradecyl, cetyl, etc., and
• X represents an anion, e.g., chloride, bromide, iodide,
• T etraalkyl quaternary ammonium salts having the general formula in which X is an anion or acid radical, for example, halide, p-toluene sulfonate, alkyl sulfate or perchlorate, R, R R and R are alkyl groups of which at least one has a chain or seven or more atoms such as carbon atoms, carbon atoms plus oxygen atoms, sulfur atoms or nitrogen atoms and ring systems, while the remaining R groups are alkyl such as methyl, ethyl, butyl, and benzyl as exemplified hereinafter.
• X is an anion or acid radical, for example, halide, p-toluene sulfonate, alkyl sulfate or perchlorate
• R, R R and R are alkyl groups of which at least one has a chain or seven or more atoms such as carbon atoms, carbon atoms plus oxygen
• the quaternary nitrogen atom may be linked through one of the R groups to a second quaternary nitrogen atom as in the bis-quaternary ammonium salts having the general structure wherein R, R and R are as just mentioned and Z is a bivalent radical as exemplified by those radicals disclosed in US. Patent 2,288,226, for example, the decamethylene radical.
• Decamethylene-a-w-bis(oxymethylpyridinium perchlorate) Laurylpyridinium perchlorate Decamethylene-bis-(oxymethyl a picolinium perchlorarate) p-Xylylene-bis-(pyridinium perchlorate) HeXamethylene-bis(oxymethylpyridinium perchlorate Hexadecylpyridinium bromide Decamethylene bis(oxymethyldimethylbenzylammonium perchlorate) Decamethylene-bis(N-methylpiperidinium perchlorate) Lauryl pyridinium-p-toluenesulfonate N-n-tetradecyl-N-methylmorpholinium-p-toluene sulfonate Lauryl trimethylammonium-p-toluene sulfonate n'Myristyl-trimethylammonium-p-toluene sulfonate Decamethylene-bis-trimethylammonium bromid
• ionic polyalkylene oxide compounds include cationic materials such as quaternary ammonium and phosphonium polyalkylene oxide salts, and ternary sulfonium polyalkylene oxide salts; and anionic polyalkylene oxide compounds such as the polyalkylene oxide carboglutamic acid salts, polyalkylene oxide-bis-N-carboxymethyl carbamate salts, polyalkylene oxide-bis-sulfuric acids, etc.
• the cationic quaternary and ternary polyalkylene oxide salts used in the invention are characterized as containing bivalent polyalkylene oxide radicals such as corresponding to polyethylene oxide, polypropylene oxide and polybutylene oxide radicals to which is attached at least one onium salt group such as a quaternary ammonium, phosphonium or ternary sulfonium salt group, and wherein n is a positive integer at least as great as 4 representing the least number of alkylene oxide units present in the polyalkylene oxide radical of the salt.
• a representative cationic salt is octaethoxy ethyl-bispyridinium perchlorate having the following formula:
• Q and Q represent organic radicals containing quaternary nitrogen atoms
• R and R represent alkylene groups
• R represents an alkyl group of from 1 to 4 carbon atoms
• n represents a positive integer of from 1 to 2
• A represents a chain of atoms of the class consisting of carbon, nitrogen, oxygen and sulfur atoms, there being less than 34 atoms present in the linear chain connecting Q to Q.
• the anion of the above ammonium and sulfonium compounds may be any acid radical not injurious to photographic emulsions, for example, p-toluene sulfonate, chloride, bromide, iodide, perchlorate or alkyl sulfate.
• p-toluene sulfonate chloride, bromide, iodide, perchlorate or alkyl sulfate.
• the introduction of halide anions into photographic silver halide emulsions alters the halide concentration in the emulsion and compensating changes in the emulsion may be desirable if such salts are employed. For this reason, it is ordinarily preferred to employ compounds containing anions other than halides. Perchlorates and p-toluene sulfonates are advantageously employed.
• p-phenylenediamine may replace the hydroquinone and thiosulfate in the formula since it functions both as a developing agent and as silver halide solvent in the processes described hereinafter.
• the emulsion is then rolled into contact with a receiving sheet containing a suitable silver precipitant and left in contact until an argental image has formed on the sheet from the silver halide transferred thereto.
• the receiving sheet in the examples was prepared as follows: The following solutions were provided:
• Jet streams of the two solutions were passed at equal rates into a funnel for rapid mixing, and thereafter the mixture was allowed to trickle through a column packed with glass helices over a period of approximately 12 seconds allowing the mixture to fall into a gelatin solution being stirred rapidly, the gelatin solution comprising 15 grams of gelatin, cc. of water, the temperature being 40 C.
• the mixing of the solutions required about 5 minutes.
• To 200 cc. of the resulting dispersion which had been stirred for 1 hour were added 2.8 grams of lead acetate. After 15 minutes of stirring, the pH was adjusted to 3.0 with 6 molar nitric acid and thereafter the composition was coated at a coverage of 2 cc. per square foot on a film base.
• the densities of the transferred positive images obtained on the receiving surfaces were read by transmission and from the resulting characteristic curves speeds were measured in units of (l-log E) where E is the exposure in meter-candle seconds required to produce a density of 0.3 above fog. Since the densities were read by transmission and the positive images were designed for viewing by reflection, the effective densities are higher than those shown in the examples. From the data in the examples it will be observed that the maximum eifectivness of the quaternary nitrogen compounds in increasing speed occurs when these compounds are used in the emulsion.
• EXAMPLE 1 Addition of quaternary ammonium salt to the emulsion An extremely high-speed bromoiodide emulsion optically sensitized with methyl -3,3-diethyl seleno carbocyanine iodide and chemically sensitized with gold and sulfur compounds was provided. Also there was added to the emulsion 2 grams per mole of silver halide of 4-hydroxy-6-met'hyl-1,3,3a,7-tetrazaindene (indicated as AZA hereafter). The amounts of the quaternary nitrogen compound indicated in the following table were then added to samples of this emulsion and the samples tested as described above:
• Hydfoqumone Sodium sulfite 80 The emulsion 0f Example 2 WES s and w Sodium hydroxide 2 5 mg amounts of quaternary nitrogen compounds were lll- Hypo 10 corporated into samples of the receiving sheet: g,i gig; g giggg 2 Il'll'g 1111 '1 ansmission 3O g g-i i nitrate V1 1 Tc S T v 1 u te Compound rl fcii v'i' D mum Water to 1 liter.
• EXAMPLE 4 The following examples illustrate usage of the ternary Addition of quaternary ammonium salt and stabilizing sulfomum Ompounds m dlfiuswn transfeir Processes agent to the emulsion
• the ternary sulfomumcompounds themselves have little solvent action on silver hahde T emulsion of p 1 was used to which had but when employed with a silver halide solvent such as been add the azain'dene Compound above, and hypo, sodium sulfite, potassium thiocyanate or potassium cadmium chloride in the amount 'S in the fOHQWiIIg bromide, the rate of solution of the silver halide through table: complexing with the solvent is increased considerably.
• a greater amount of the silver Compound Grams per speed halide is made avaliable for formation of the positive mole AgX image on the receiving sheet.
• a smaller amount of silver halide solvent 393 or a weaker silver halide solvent can be used in the 427 system.
• a developer may be used contain- 32 422 ing /3 to /3 of the usual amount of hypo and a speed 5 427 increase of about 0.45 log E is obtained when the onium 2% compound is also present. Similar effects are obtainable 439 when sodium thiocyanate and to a lesser extent high concentrations (50200 grams per liter) of potassium bromide are substituted for hypo.
• a weak image can even EXAMPLE 5 be obtained with sodium sulfite in the presence of the onium compound.
• the onium compound Addmon of asulfomm. salt to the develop? in the developer in concentrations of the order of 1.0 quaternary ammomum salt to the emulsmn gram per liter, an increase in speed of about 0.15 to To a high-speed bromoiodide emulsion optically sensi- 0.30 log E is readily obtainable.
• a warmer toned image is obtained with loss fur and gold compounds, were added 2 grams of AZA, of maximum density partly because of development of 0.4 gram Quat.
• the maximum effectiveness of the ternary sulfonium compounds occurs when they are used in the developer compositions and is generally accompanied by either no change or an increase in maximum density of the transferred positive image as compared to a developer free of the sulfonium compound.
• EXAMPLE 7 sulfonium compound in developer
• the receiving sheet was prepared as follows: A solution containing 100 cc. of water and 1 cc. of 0.5 molar sodium sulfide was added in 1 minute and 20 seconds to a solution of 1 cc. of 0.5 molar zinc nitrate and 0.5 cc. of 10 percent gelatin solution in 375 cc. of water at 40 C. Twenty-five cc. of a 10 percent gelatin solution were then added and 1.5 grams of lead acetate and a suitable gelatin hardening agent. The resulting composition was then coated at a coverage of 6 cc. per square foot upon a film support.
• the emulsion used was a medium-speed bromoiodide emulsion.
• the developer had the same composition as the standard hydroquinone developer given preceding Example 1 except that the hypo was reduced from the normal level of 14 grams to 7.5 grams per liter and 0.95 gram of dimethyl n dodecyl sulfonium p toluene sulfonate was added per liter.
• the diffusion transfer process of Example 1 was carried out with the result that a speed increase of 0.3 log E in the shoulder regions, a 0.6 log E increase in the toe regions of the characteristic curve, a maximum density increase of about 0.15 and a slightly colder tone was obtained compared to the same emulsion processed in the standard hydroquinone developer free of the sulfonium compound and containing the higher level of hypo. By transmission the increase in density was 0.42.
• EXAMPLE 8 Sulfonium compound in developer A receiver was prepared by first mixing rapidly a solution comprising Water cc 1200 0.5 M sodium sulfide cc 6.0
• the negative consisted of a gelatino-silver bromoiodide emulsion containing 6.3 mole percent iodide, optically sensitized with methyl-3,3-diethyl-seleno-carbocyanine iodide, and containing the antifoggant 4-hydroxy-6-methyl- 1,3,3a,7-tetrazaindene.
• the emulsion was coated on film support so as to obtain 0.09 g. silver and 0.50 g. gelatin per square foot.
• the developer was the same as the standard hydroquinone-control developer except that 0.5 gram per liter of the sulfonium compound of Example 7 was used.
• a speed gain of 0.45 log E was realized over the same process in which the sulfonium compound was omitted from the developer.
• the increase in D max. was 0.15 (by reflection) and 0.07 (by transmission).
• EXAMPLE 9 Sulfonium compound in emulsion
• EXAMPLE 10 Sulfonium compound in receiving sheet
• the emulsion, developer and procedure of Example 7 were employed with the receiving sheet of Example 8 above to the coating of which had been added 1.0 gram of the sulfonium compound of Example 7.
• An increase in density of 0.15 was obtained in the positive compared to the control process where the sulfonium compound was absent from the receiving sheet.
• EXAMPLE 11 Sulfonium compound in receiving sheet The process of Example 10 was carried out except that the receiving sheet consisted of a water resistant paper sheet carrying a gelatin coating containing colloidal silver and 15 milligrams of the sulfonium compound of EX- ample 7 per square foot. The image obtained in the positive was brown in color and of significantly higher density compared to a light yellow image contained in the control process using the same receiving sheet free of sulfonium compound. A D max. (transmission) 0.37.
• EXAMPLE 12 Sulfonium compound in developer The process of Example 11 was carried out except using 2.0 grams per liter of the sulfonium compound only in the developing solution. The same improvement in image tone was obtained. The maximum density (trans-. mission) was 0.73, compared with 0.16 for the control.
• EXAMPLE 13 sulfonium compound in developer
• the receiving sheet of Example 1 and a fast bromoiodide emulsion were used in the process.
• the standard hydroquinone developer contained 0.4 gram per liter of Sulf. I.
• a speed gain of 0.15 log E was obtained compared to the control process using no sulfonium compound in the developer.
• azaindene stabilizing agents suitable for use in the invention as indicated above are those such as described in the Carroll et al. US. patent application Serial No. 627,135, filed December 10, 1956, as follows: 4- hydtoxy-6-methyl-l,3,3a,7-tetraazaindene, carboxy-4- hydrox -1,3,3a,7-tetraazaindene (Reynolds et al. U. S.
• Additional ingredients useful in the emulsion of the diffusion transfer process of the invention include the noble metal salts of group VIII of the periodic table, gold, salts, reducing agents, mercury compounds and various combinations of silver halides disclosed in the Carroll et al. US. patent application Serial No. 627,135, filed December' 10, 1956, now US. Patent 2,944,902 granted July 7, 1960.
• suitable colored or colorless coupler compounds of the phenolic hydroxyl, pyrazolone and open-chain reactive methylene types may be employed in the emulsion, receiving sheet, or developer.
• the quaternary ammonium and ternary sulfonium compounds indicated are similarly beneficial for use with other types of diffusion transfer processes such as that disclosed in the Yackel et al. US. patent application Serial No. 586,705, filed May 23, 1956, wherein a unitary element is provided having, for example, a removable cellulose ether phthalate silver halide emulsion layer coated upon a receiving layer containing a silver precipitant.
• the quaternary ammonium or ternary sulfonium compound may be present in either the emulsion, the receiving layer or the developer solution.
• the element is exposed in a suitable manner, development initiated in the presence of a silver halide solvent and a positive image formed in the receiving layer accompanied by removal of the overlying emulsion layer containing the negative image.
• the indicated quaternary ammonium salts are used in the process of the Yackel et al. invention, it is advantageous to also employ one of the azaindene stabilizing compounds preferably together with a tone modifying agent. That is, when a high speed coarse-grained emulsion is to be used containing the cellulose ether phthalate vehicle and a minimum of gelatin, the stability of the emulsion is increased by adding an azaindene compound such as mentioned in Example 9 above.
• the stability conferred by this compound is greater than obtainable with antifoggant compounds of the benzothiazole and mercaptotetrazole types; however, a loss in D mm is sustained and it is desirable to further add a quaternary nitrogen compound such as Quat. II above to restore D max, and preferably also 2-mercapto-5-phenyl-1,3,4- oxadiazole to improve the tone of the image.
• 3-pyrazolidone silver halide developing agents which may be employed in the developer composition alone or in conjunction with other silver halide developing agents such as hydroquinone are disclosed in the James US. Patent 2,571,300, granted June 19, 1956, for example, 1-phenyl-4,4-dimethyl-3-pyrazolidone. Such usage of the pyrazolidone compounds may be alone or in conjunction with ascorbic acid for the purposes disclosed in the patent. Also, the silver halide developing agents may be present in the emulsion layer rather than in the alkaline solution containing the silver halide solvent.
• developer compositions exemplified above containing the combination of a silver halide solvent, a 3-pyrazolidone developing agent, a hydroquinone such as hydroquinone, per se, toluhydroquinone, and chlorohydroquinone, and one of the mentioned quaternary ammonium salts, especially the cyclammonium quaternary salts are especially useful in the diffusion transfer processes.
• quaternary salts are employed in the diffusion transfer processes in conjunction with certain tone modifying compounds, pronounced improvement in image tone is obtainable even when the processes are carried out at moderately low pH.
• Suitable quaternary salts are those mentioned above.
• the following quaternary salts are representative cyclammonium quaternary salts, which are particularly effective in combination with the tone modifying compounds.
• Tetradecamethylene-bis (pyridinium perchlorate) a-Dimethyldithiocarbamatoethyl-N-methyl pyridinium -ptoluene sulfonate Decamethylene-ot,w-bis-(oxymethyl pyridinium perchlorate) 3,6,9,12,15,18,21,24 octahexacosane 1,26 bis(5-ethyl- Z-methyl pyridinium methane sulfonate) Z-B-phenethylisoquinolinium bromide l-p-phenethylquinolinium bromide 3,14-dioxahexadecane-1,16-bis-(pyridinium methane sulfonate) 13 l-methyl-Z-nonanoyl pyridinium p-toulene sulfonate Heptoxymethyl-Z,4,6-trimethyl pyridinium chloride
• this compound and other similar quaternary ammonium bases and salts which consist of an onium radical attached to short chain aliphatic groups such as tetramethyl ammonium hydroxide, tetraethyl ammonium hydroxide, tetra-n-propyl ammonium hydroxide, tetra-kis(2-hydroxy-ethyl)ammonium hydroxide, or the halide, perchlorate, or p-toluene sulfonate salts of these bases, are not suitable for the purposes of this invention.
• the mentioned tone modifying compounds which are useful in combination with the quaternary salts, and which are particularly useful in combination with the cyclarnw monium quaternary salts given immediately above, are the following cyclic and open chain sulfur and nitrogencontaining compounds which are characterized as being organic compounds forming with silver ion, such as present during the transfer of dissolved silver halide, a silver compound less soluble than silver bromide in water and solutions of silver halide solvents. It is known that some of these organiccompoundsare useful in controlling the tone of silver images but as mentioned above and shown in the examples hereafter pronounced improvement in tone results when these organic sulfur and nitrogencontaining compounds are used in combination with the onium compounds compared to using either compound alone.
• the tone-modifying effect does appear to be related to the fact that in the diffusion transfer processes the compounds all form with the silver halide of the emulsion, silver salts less soluble in water than silver chloride or silver bromide.
• g r 1 1 23 ment of the sensitive elements of the above Yackel et a1.
• neutral toned images being obtained by development for two minutes at 68 F.
• the first five materials are dissolved in approximately 750 cc. of water at 90 F.
• the benzothiazolium methyl metho sulfate and the tetradecamethylene-bis-pyridinium perchlorate are dissolved in 50 cc. of warm water.
• the solutions are then added to the bulk solution which is then made up to one liter with cold water.
• the solution has a pH of approximately 10.1.
• EXAMPLE 18 A gelatin solution (250 cc.) was diluted with 750 cc. water. 2.5 cc. of 1 N Na S were then added to the solution. 250 cc. of water containing 2.6 cc. of 1 N zinc nitrate were added slowly to the sulfide solution through a jet, resulting in the formation of a colloidal dispersion of zinc sulfide. To this dispersion were added 10 liters of a 3% gelatin solution, 300 cc. of a 7.6% saponin solution and 134 cc. of a 10% formaldehyde solution. The mixture was dispersed at 40 C. and then coated on a photographic paper support at a coverage of 2 1b. of solution per 100 sq. ft. of coated surface and dried, forming the silver precipitating layer.
• cellulose ether phthalate an ethyl cellulose containing 45.8% ethoxyl phthalated to 22.7% phthalyl
• tone modifying compound S-nitroindazole, or the quaternary ammonium salt, 3,6,9,12,l5,18,2l,24-octoxahexacosane 1,26,bis (5-ethyl-2-methylpyridiniummethane sulfonate), is omitted from the developer solution, an unacceptable, warm-toned positive image is obtained.
• Example 19 The process of Example 18 was carried out using the same developer solution but in which S-nitroindazole was replaced by benzothiazolium methyl metho sulfate in like amount to also obtain a neutral-toned image. The omission of either of the nitrogen-containing compounds from the developer solution yields a warm-toned positive image.
• Example 20 The procedure of Example 18 was carried out with a number of developer solutions in which the pyridinium salt was replaced with the same amount of each of the following cyclammonium quaternary salts:
• Example 21 The procedure of Example 18 was carried out with a number of developer solutions in which 5-nitroindazole was replaced by the same amount of benzothiazolium methyl metho sulfate and the pyridinium salt replaced by one of the following cyclammonium quaternary salts:
• Tetradecamethylene-bis (pyridinium perchlorate) a Dimethyldithiocarbamathoethyl N methyl pyridinium-p-toluene sulfonate Decamethylene-a,w-bis-(oxymethyl pyridinium perchlorate) 2-,8-phenethylisoquinolinium bromide 3,l4-dioxahexadecane-l,l6bis-(pyridinium methane sulfonate) l-methyl-Z-nonanoyl pryidinium-p-toluene sulfonate HeptoXymethyl-2,4,6-trimethyl pyridinium chloride Tetradecamethylene-bis-(trimethyl ammonium perchlorate) 3-methyl-2,[3-phenethyl isoquinolinium bromide 25 4,4,10.10 tetraoxo 4,10 dithiatr-idecane bis (pyridinium perchlor
• Example 22 The process of Example 18 was carried out with separate developing solutions except containing the following quaternary salts in place of the pyridinium salt of the Example 18 solution.
• EXAMPLE 23 The inadequacy of the short chain quaternary ammonium salts to improve the tone of the solvent transfer images was demonstrated by carrying out the procedure of Example 18 except using tetramethylammonium chloride, tetra-n-propylammonium chloride and trimethylphenylammonium chloride respectively as the quaternary salt in the following solution, development being carried out for 2 min. at 68 F.
• the acidic solution may contain a metal salt as titanous chloride, a metal ion chelating compound such as ethylenediamine tetraacetic acid and a silver halide solvent such as hypo as follows:
• Titanium trichloride solution (20%) 'cc 150 Ethylenediamine tetraacetic acid tetrasodium salt grams 100 Sodium thiosulfate.5H O do 20 Water to make liter 1 pH adjusted to 4.0.
• a suitably exposed emulsion is immersed in the solution briefly, then squeegeed in contact with a receiving sheet such as described above until a silver image is formed in the receiving layer.
• Other chelating agents such as iminotriacetic acids, oxalic, tartaric, etc. may be substituted in the developer solution.
• Another method for preparing developer compositions which are appreciably less alkaline than those prepared with caustic alkali or alkali carbonate includes using an organic alkaline buffer compound as the source of alkali.
• the buifer compounds are reaction products of sulfur dioxide and amino alcohols such as 2-diethylamino ethanol sulfite, 2-aminoethanol sulfite, 2-ethylaminoethanol sulfite, Z-methylaminoethanol sulfite, Z-dimethylaminoethanol sulfite.
• One advantage of the use of the buffer compounds lies in the fact that they permit the preparation of highly concentrated developer solutions which can be diluted with as much as forty parts of water without appreciable loss in activity.
• a representative formula containing the buffer compounds is as follows:
• the composition can be diluted to one liter for use and as such has a pH of 9.8.
• the effective amines include the primary aliphatic amines containing a linear carbon chain of from 4 to 6 carbon atoms, that is, amines of the normal butyl to hexylamine series. Surprisingly, lower and higher members of the series e.g., propylamine and heptylamine, are ineffective.
• amines which are effective are the a,w-alkylene diamines containing from 8 to 12 carbon atoms in the alkylene chain separating the amino groups, as in the series from oc,w-0Ctyln6 diamine to a,w-dodecylene diamine.
• one of the amino groups of the diamine may be replaced by a hydroxyl group as in the alkanolamines.
• benzylamine and cyclohexylamine are useful for the same purpose.
• These amines are advantageously used in the developing solutions containing developing agent and silver halide solvent used for initiating development of the sensitive element, in concentrations up to about 0.5%.
• a representative developer composition especially usefully in those processes is as follows:
• butylamine may be replaced in similar quantity by other amines such as disclosed above or one of the amines in combination with one of the above-mentioned sulfur and nitrogencontaining tone modifying compounds.
• the sulfite addition compound can be replaced by sodium sulfite by adjustment of the developing agent and silver halide solvent concentrations.
• the above solution was used to develop sensitive elements such as shown in the examples of Yackel et al. US. patent application Serial No. 586,705 for 2 minutes at 68 F.
• tone modifying compound benzothiazolium methyl metho sulfate is omitted, a weak positive image is obtained. If, on the other hand, the methylimino bispropylamine is omitted, no positive image is obtained.
• Tetradecarnethylene-bis-(pyridinium perchlorate) a-Dimethyldithiocarbamatoethyl-N-rnethyl pyridinium p-toluene sulfonate N-methyl-2-N-propyl mercapto pyridinium perchlorate Decamethylene-a,w-bis-(oxymethyl pyridinium perchlorate) 3,6,9,12,15,18,21,24 octaoxahexacosane 1,26 bis-(5- ethyl-Z-methyl pyridinium methane sulfonate) 2-fi-phenethylisoquinolinium bromide l-fi-phenethylquinolinium bromide 3,14-dioXaheXadecane-1,16 his (pyridinium methane sulfonate) l-rnethyl-Z-nonanoyl pyr

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