Classifications

• • C—CHEMISTRY; METALLURGY
  • C05—FERTILISERS; MANUFACTURE THEREOF
  • C05B—PHOSPHATIC FERTILISERS
  • C05B11/00—Fertilisers produced by wet-treating or leaching raw materials either with acids in such amounts and concentrations as to yield solutions followed by neutralisation, or with alkaline lyes
  • C05B11/04—Fertilisers produced by wet-treating or leaching raw materials either with acids in such amounts and concentrations as to yield solutions followed by neutralisation, or with alkaline lyes using mineral acid
  • C05B11/06—Fertilisers produced by wet-treating or leaching raw materials either with acids in such amounts and concentrations as to yield solutions followed by neutralisation, or with alkaline lyes using mineral acid using nitric acid (nitrophosphates)
• • 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
  • G03C1/00—Photosensitive materials
  • G03C1/72—Photosensitive compositions not covered by the groups G03C1/005 - G03C1/705
  • G03C1/73—Photosensitive compositions not covered by the groups G03C1/005 - G03C1/705 containing organic compounds
• • 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
  • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
  • G03C5/58—Processes for obtaining metallic images by vapour deposition or physical development
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
  • Y10S430/167—X-ray
  • Y10S430/168—X-ray exposure process

Definitions

• the in vention does not relate to the use of silver halide as a photo-sensitive material.
• a silver image which is weak or even not perceptible by the eye is produced in the layer--hereinafter referred to as the silver germ image-which is subsequently intensified by physical development.
• the term physical development within the scope of the invention is to be understood to mean the growth of a weak metallic image to form an image of sufficient photographic'density, the image silver produced by reduction at least in part not originating. from rare metal ions locally present in crystallised connection.
• rare metal is to be understood here tomean a metal which is classified above the copper inthe electrolytic voltage series of metals. It thus includes inter alia silver, mercury, gold andqthe platinum metals; in most cases silver is preferred.
• the silver germ image usually has only a small capacity of being intensified, so that apart from an improvement in blackening and in colour, the amount of light required for producing the final contrast is decreased little or none by physical development. From the investigation leading to the invention and in which use is made of the experience gained with layers containing diazoand mercury compounds, it appears probable that the reason for the low intensifiability of the silver germ image must not be sought in a'small yield of the primary light reactionthis is in the said cases of the same order as the yield of the primary light reaction with the silver halides-but that this small intensifiability is attributable to the low degree of dispersion of the silver germ image to be developed.
• the extent of intensification of the silver germ image by physical development and hence its degree of dispersion may advantageously be influenced by certain steps to be mentioned hereinafter, in regard to the medium used during the formation of the silver'germ image.
• a pH-value of 1 may, in view of the properties of the material of the layerand/or the binder, be considered as extreme permissible value, whilst on the other hand the pH must, as a rule, not be higher than 13 in view of the conversions of the material of the layer and/or binder under the action of strong alkali.
• the term redox potential of the light-reaction product' is to 'be understood here to mean the potential assumed by an indifierent electrode, for example a platinum electrode, in a solution of the light-reaction product and of the product obtained therefrom upon oxidation by silver ions, measured with respect to the normal hydrogen electrode.
• silver potential is to be understood here to mean the potential assumed by a silver electrode in a solution containing silver ions, measured with respect to the normal hydrogen electrode.
• EAg 0.80-0.06 pAg' being the silver potential, and pAg the negative logarithm of the activity of the silver ions. If it is necessary to determine the silver potential at a pH value higher than 7, use may conveniently be made of the formula for pAg:
• the value of the normal redox potential is in .the majority of cases dependent upon acidity (pH), the infinence of the pH value becoming manifest in that the normal redox potential decreases upon increase of the pH, whereas the analytic concentrations of the light-reaction product and its oxidation product remain unchanged.
• the extent of the decrease in normal redox potential per pH-unit varies between volt and 0.09 volt and is frequently 0.06 volt. It may furthermore have difierent values in one and the same redox system in different pH-ranges.
• the value of the normal redox potential is dependent upon the presence of substances capable of binding themselves to different extents with the components of the redox system.
• the degree of intensifi: cation of the silver germ image by physical development is determined by the difference AE between the said two potential values. More particularly it has been found that it is possible to increase the intensifiability of the silver germ image by increasing the difference AE, which is achieved by providing for the silver potential to be increased and/ or the normal redox potential of the lightreaction product to be decreased during the formation of the germ image.
• an intermediate phase that of the formation or the introduction of germs.
• A-method of reducing the normal redox potential of the light-reaction product consists in that before or during the formation of the silver germ image substances are introduced into the layer which bind themselves with the oxidation product of the light-reaction product obtained by the conversion between the light-reaction product and the silver ions, to a greater extent than with the light-reaction product itself.
• the means usedin this 'method naturally varywith the photo-sensitive substance used. If this-is, for example, a ferric salt, then pyrophosphates, fluorides, citrates and oxalates, for example, have the effect of reducing the redox potential of the lightreaction-product and are thus fundamentally serviceable.
• the light-reaction product is, for example, hydroquinone, which is the case if. p-diazophenolisfusedas the photo-sensitive substance, the addition of sulphite to a line vapour or with arliquid, the pH-value of-which is I higher than that of the layer and' more particularly with a liquid the pH-value of which is at least 7..
• Use is preferably made of bufier mixtures to enhance the reproducibility of the method. f.
• the said technique provides a method'of improving the possibility of intensifying the silver germ image.
• the layer is treated in such manner that during the formation of the silver germ image the silver poten-' tial in the layer is increased--'which at a pH-value smaller than about 7 make take place by increasin'gthe silver-ion concentration in the layer-and/or the redox potential in'the layer is decreased, which may takev place either by increasing the pH in the layer or by binding the oxidation product of the light-decomposition product.
• a larg number of, substances are fundamentally serviceable for the method heredescribed, an intensifiable germ image being provided in a layer.
• the use ofgthe'invention' requires that the photo-sensitive substance is adapted to be converted by radiation into a light-reactionproduct capable of reducing silver ions to form silver metah
• the light reaction may be coupled to take place in the presence of the silver compound from which the latent image is produced by cellulose,-a pH-value up to 11 is permissible.
• this fogging may he avoided in that the development of the silver germ image already produced is preceded by treatment of the layer with a liquid capable of dissolving silver metal and/or silver compounds.
• a treatment with dilute oxidising acid, such .as nitric acid, or a solution containing ferricyanide and thiosulph'ate is particularly suitable: These liquids must react for a short time only and the concentrations of the dissolved substances'must not be unduly high, since otherwise .the silver germ-image is also dissolved. Considering the increase in sensitivity obtained after physical development, the silver germ image is attacked to a much smaller extent than the latent fog.
• the concentrations of the baths mustnot be unduly low since otherwise the desired effect is not obtained. However, the concentrations must neither be unduly high and the reaction period of the baths must not be undulylong in order to restrict the attack of the silver germ image to a negligible minimum.
• impregnation ofthelayer in a 5% sodium-thiosulphate solution inwater for 3 minutes we may mention here impregnation ofthelayer in a 5% sodium-thiosulphate solution inwater for 3 minutes. Otherwise it is advisable in each individual case to determine the suitable composition of the values by a single test.
• AE acquires a value suitable for satisfactory or even maximum intensification of the silver image-hence by impregnating the layer in a solution having a pH-value such that AE comes within the range between ().2 and 0.8 volta layer is obtained which is more serviceable than would be possible without this step, since it has been found that in such layers the phenomenon of so-called regression occurs to a smaller extent than if use is made of, for example, neutral layers.
• regression is to be understood to mean that the silver germ image is produced to an extent which is smaller as the time between exposure and formation of the silver germ image is longer.
• a lyophile layer may be utilised consisting, for example, of regenerated cellulose, superficially saponified cellulose ester or paper.
• a layer is sensitised, for example by impregnation in an aqueous solution containing the photo-sensitive material and, if desired, silver compounds and or substances the object of which is to adjust the pH in the layer to a given value.
• a binder such as gelatine, together with the above-mentioned solution, to be dried on a support.
• the layer thus obtained which has been exposed and contains an amount of silver compound sufiicient for the formation of the silver germ image, is treated with a liquid having a pH-value higher than the initial pH-value of the layer, or the layer is treated with an alkaline vapour. If, as may be examined beforehand, fogging during development does not occur, the layer subsequent to the adjustment of the pH-value may be treated with a developer. If fogging does occur then development is preceded by a treatment with a fog-eliminating liquid as mentioned be- By providing that, after exposure, the conditions amber-a fore. As previously stated, fogging always occurs if the pH-value during one of the treatments is higher than about 7. At lower pH-va'lues fogging occurs only when using particular photo-sensitive compounds such as diazonium compounds and methylene-blue.
• a layer which has been exposed and contains an amount of silver compounds sufiicient for the formation of the silver germ image may be treated with an alkaline liquid which also dissolves silver compounds from the layer in order to avoid fogging.
• a solution of thiosnlphate, the pH of which is adjusted to a value between 8 and 12 by the addition of buffering substances and/or alkalis is particularly suitable for this purpose.
• the silver compounds required for the formation of the silver germ image may frequently be provided in the layer prior to exposure. This is effected in the simplest way by dissolving this compound in the liquid by which the layer is sensitised. In this case also use may be made of the above-mentioned simplification by combination of alkaline treatment and dissolution of silver compounds.
• the treatments may be simplified by treating the layer, subsequent to exposure, with a solution of silver compounds which also raises the 'pH-value of the layer.
• Physical development such as is used according to the invention, consists in reaction of a solution containing a rare-metal compound and a reducing agent, upon the silver germ image.
• the rare metal compound commonly used is 'a silver compound, usually a silver nitrate, so that the final contrasts have a grey to grey-black colour.
• developers containing a compound of other rare metals such as mercury or platinum.
• the reducing agent being used is, for example, hydroquinone.
• such developers usually contain further substances such as alkalis, acids and salts.
• a suitable developer contains, for example, in addition to a reducing agent and a silver salt, alkaline hydroxide and alkaline sulphite.
• a developer containing citric acid is particularly suitable, the contrast then becoming of a neutral grey colour a short time after the beginning of the development so that contrasts of satisfactory colour may be obtained with the use of these developers, which contrasts have a lower gradation than those obtainable With the use of other developers.
• the gamma increases as the time of development is longer.
• the photo-sensitive layer according to the invention which layer contains a photo-sensitive compound having a light-reaction product of low solubility or incapable of diffusion, leads to the additional effect of an increased resolving power even if the layer is not provided with a silver compound until after exposure.
• This may be achieved by means known per se such, for example, as by the introduction into the photosensitive compound of an aliphatic chain comprising at least 8 carbon atoms.
• Suitable examples of such substances are the aforementioned ferriand uranyl compounds.
• photo-sensitive organic substances reduced by exposure and the light reaction product of which also satisfies the aforementioned condition are likewise suitable.
• photo-sensitive organic materials are, for example, benzoquinone and its derivatives which, upon irradiation, change to multivalent' phenols.
• Other suitable photo-sensitive organic substances which have not been used hitherto in photography are colouring matter such as indophenols, indamines and indanilines, which are converted by exposure into their leuko compounds.
• Light-reaction products reducing more strongly are obtained, for example, by the exposure of colouring matter belonging to the azine-, oxazine-, thiazineand indigo classes.
• the colouring physical development can always be used.
• Example I superficially saponified cellulose acetate foil is sensitised by impregnation in a solution containing 0.21 g./mol. of ferri-nitrate, 0.23 g./mol. of silver nitrate and 0.15 g./mol. of citric acid per litre water, and subsequently dried.
• AB Due to the treatment with the last-mentioned solution, AB is increased from 0.13 volt to 0.44 volt.
• the value 0.75 volt is that of the silver potential of the sensitising solution measured in a solution of 0.23 g./mol. of silver nitrate and 0.15 g./mol. of citric acid per litre water; this'value is not varied due to the step concerned.
• the value 0.62 volt is that of the normal redox potential measured in a solution containing ferri- 'nitrate developer.
• the use of the step according to the invention hence by the treatment with a solution containing 0.5 .g./mol. of sodium lactate per litre water for 0.5 minute, has the effect of decreasing the normal redox potential from 0.62 to 0.31 volt. The latter value has been found by measurement on a solution containing ferrinitrate and ferro-nitrate in a common concentration of 0.10 g./mol. in a litre of 0.5 g./mol. of sodium lactate solution in water.
• Example II A film of superficially saponified cellulose acetate is impregnated in a solution containing 0.01% of methyleneblue and 0.1 n sulphuric acid and subsequently dried.
• the blue-green film which absorbs red light but which freely transmits blue and green radiation is exposed with the use of an incandescent lamp, treated with a solution of 0.5 g./mol.
• the light-reaction product of methylene-blue has a comparatively lowsolublity, ,so that a suflicient resolving power is obtainable despite the fact that the layer does'not cont'ain'any silver compound during ex posure.
• the photo-sensitive colouring matter used may be other thiazine colouring matter, such as Lauths violet, or azine colouring matter, such as Janus green, or oxazine colouring matter such as brilliant cresyllue.
• Example III nitrate in ccs. of water (pH-16.5; AE thus varies from-.1 Subsequently, in
• Example IV A film consisting of superficially saponified cellulose acetate is sensitised by impregnation for 2 minutes in a solution containing 2.67 gms. of p-d'iethylaminobenzenediazoniumboronfiuoride and 0.85 gm. of silver nitrate in 100 ccs. of water, and subsequently dried in air.
• the value AB is in this case about 0.1.
• the dry film is exposed behind a sensitometer with the use of a mercury-vapour lamp.
• the film is now treated with a 10% solution of sodium acetate (pl-l: 8.5) for l minuteso that the value of AB is increased to about 0.4 volt-and subsequently with a 10% solution of sodium thiosulphate in water for 3 minutes.
• a 10% solution of sodium acetate pl-l: 8.5
• a 10% solution of sodium thiosulphate in water for 3 minutes.
• physical development takes place for 8 minutes with a solution containing 0.2% of Metol, 0.7% of citric acid and 4% of silver nitrate, followedby washing and drying.
• a beautiful black copy of the sensitorneter is then obtained, the blackening curve of which has a gamma value of 1.3, the highest blackening being about 3.
• the gamma value is 2.3 after development for 4 minutes and. 8 after development. for-8 minutes.
• the highest blackening in the. copy is then greater than 3.
• the sensitivity is 500 times higher. With, respect to. the case in which physical development only takes place after exposure, a gain in sensitivity of a factor 50 to 100 is obtained. In the latter case fogging frequently occurs in the physical development.
• Example V A film consisting of superficially saponified cellulose acetate is impregnated for 2' minutes ina solution containing 1.66 gms. of p-aminobenzenediazonitunboroniiuoridcv and 1.5. gms. of silver nitratein. 10.0 ccs.. of'water. The value of AEis in this case about 0.1. volt.
• the gain in sensitivity with respect to the method of German patent specification 601,676. is. in this case a factor 100.
• the gain in sensitivity with respect to the case in which physical development only takes place, is a factor 20.
• Example VI superficially saponified cellulose acetate is impregnated in a solution of 4 gms. of the chlorinebenzene sulphon-acid salt of p-diazophenol and 4 gms. of silver nitrate in ccs. of water.
• the value of AB is in this case about 0.16 volt.
• the gamma value is 0.5 and the highest blackening is l.
• the colour is brown-black, the gain in sensitivity with respect to the method of German patent specification 601,676 being a factor 150.
• the gain in sensitivity with respect to the method in which physical development only takes place, is a factor 10.
• Example VII A film of superficially saponified cellulose acetate is impregnated in the solution containing 2.29 gms. of hydroxy-l, diazoniurn-Z, methyl-6,. benzenesulphonic acid- 4, together with 3.33 gms. of silver nitrate and 2 gms. of citric acid per 100 ccs. of water. After exposure, the film is treated with the following solutions: 10%. soda solution (pH: 10.6) for 1.5 minutes, 10% solution of potassium rhodanide for 4 minutes, physical development of Example I for 5 minutes. The result, is a black sensitometer copy having a gamma-value of 1.7 and at highest blackening of 2. The sensitivity is about 200 times that obtained by the method according to German patent specification 601,676 and also about 200 times that, which is obtained if the treatment with the two firstrmentioned solutions is omitted.
• the sensitising solution instead of containing the above-mentioned diazonium compound, contains 2.67 gms. of diazoniurn-1, naphthol-Z, sulphonic acid-4, then after a similar treatment the gamma-value is 2.5 and the highest blackening is more than 3, the gain'in, sensitivity being of the same order of magnitude.
• Example VIII Non-glued paper is impregnated in a solution of +2.5 gms. of amino-1 dimethoxy-2.5 benzene diazonium-boronfluoride-4 in 100 ccs. of acetane. Then again impregnation takes place in a solution of 1.7 gms. of silver nitrate and 2 gms. of citric acid in 100 ccs. of Water. The value of AB is in this case about 0.34.
• Example IX from about 0.04 to about 0.39 volt) and washed. This is followed by a-treatment with a solution of 0.37 g. of potassium ferricyanide and 1.25 gms. of sodium thiosulphatein100 ccs. of water. After renewed washing development takes place in a solutionof metol (0.5%), tartaric acid (1%) and silver nitrate (0.5%) for 12 minutes.
• the copy obtained is grey-black with a violet colourpthe gamma-value is 2.5 and the greatest blackening is more than 3.
• the sensitivity is about 70times as high as.that obtained by the method according to German patent specification 601,676.
• Thepositive copy obtained is of a beautiful blackness, of satisfactory sharpness and beautiful gradation.
• anexposure sufiices which is 100 times-smaller than if the'same m'aterial is treated in accordance with German patent specification 601,676, or if physical development only takes place.
• images of a high gamma value are obtained.
• Example X Superficially saponified cellulose acetate issensitised with a. solution of 2.67 gms. of p-diethylaminobenzenediazoniumboronfluoride and 3.4 gms. of silver nitrate in 100Jccs. of water and dried. Subsequently, 4 pieces are exposed and each treated in one of four alkaline solutions of 15% sodium thiosulphate, obtained by adding 10% of sodium acetate, 3% of borax, 10% of soda and 1.7% of piperidine respectively. After washing, all four strips are physically developed for 8 minutes in a developer containing 0.2% of metol, 0.7% of citric acid and 0.4% of silver nitrate.
• the pH value of the alkaline thiosulphate solutions is 859.1, 10., and 12 respectively.
• the gammavalues of the copies are about 2, and the highest black- Example XI
• a clear black image is produced having a gamma-value of about 0.5 and a maximum blackening which is slightly higher than 1. If use is made of a 15 times greater exposure and if the physical development is precededby treatment with a solution of silver nitrate in water exhibiting the same pAg as the above-mentioned solution of silver nitrate and sodium lactate, an image is obtained which is barely perceptible only.
• the film after the soda treatment, is introduced into 35 ccs. of a 2% solu tion of ammonium rhodanide in water. After being left in this bath for 4 minutes, 5 ccs. of each of the following three solutions are added whilst stirring the liquid:
• Example XIII I A foil of superficially saponified cellulose acetate is sensitised by impregnation for 2 minutes in 0.1 n nitric acid in which 0.75% of benzoquinone and 0.5% of silver nitrateare dissolved, and subsequently dried.-
• Exposure behind a sensitometer with the. use of a mercury vapour lamp is followed by treatment with 0.5 11 solution of ammonia in water for 2 minutes. After washing, development takes place for 2 minutes in a developer consisting of 1% of metol, 3.5% of citric acid and 0.4% of silver nitrate in water. A satisfactory, neutral-grey copy of weak gradation is obtained.
• the gain in sensitivity with respect to the cases in which the ammonia treatment and the physical development respectively are omitted, is certainly a factor 25 to 30.
• the value AB is here decreased by the treatment with ammonia from 0.05 to about 0.04 volt.
• Example XIV Strips of the exposed film of Example I are treated for 0.5 minute in one of the following solutions:
• the strips are treated with a 0.3 n solution of ammonia in water forZl minute. After washing,
• Example XV A film of superficially saponified cellulose acetate is sensitised by impregnation in a solution containing 0.25 g./m ol. of uranylnitrate, 0.23 g./rnol. of silver nitrate and 0.08 g./mol. of citric acid per litre water, and subsequently dried.
• a strip After exposure under a. sensitometer with the use of a mercury vapour lamp, a strip is treated in the solution (b) of Example XIV for 0.5 minute, subsequently bathed in a solution of sodium thiosulphate in water for 3 minutes and after washing for 7 minutes, physically developed in the developer of Example I for 5 minutes. Another strip is treated in the solution (c) of Example XIV for 3 minutes. After washing, this strip is also developed in the same developer for 5 minutes. Satisfactory, black copies of the sensitometer are obtained. The gain in sensitivity with respect to the method in which physical development only is used is a factor 100 and 25 respectively.
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7.0 and containing a light sensitive compound selected from the group consisting of diazonium, azine, oxazine, thiazine and indigo compounds, indophenols, indamines, and indanilines to decompose said compound at selected portions of the layer, said layer after exposure having a AB, in the presence of a water-soluble silver salt, of less than 0.8volt, treating the exposed layer with an alkaline medium and moisture in the presence of said water-soluble silver salt to form a latent silver contrast, the alkalinity of the alkaline medium being sufiicient to increase AB to a value greater than at least 0.2 volt, and physically developing the latent contrast by then applying to said layer a developingsolution containing a salt of a metal higher than copper in the electromotive series and reducible to metal in solution and a watensoluble reducing agent.
• a light sensitive compound
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7 .0 and containing a' light sensitive oxazine compound to decompose said compound at selected portions of the layer, said layer after exposure having 21 AB, in the presence'of a water-soluble silversalt, of less than 0.8 volt, treating the exposed layer with an alkaline medium and moisture in the presence of said water-soluble silver salt to'form a latentsilver contrast, the-alkalinity of the alkaline medium being sutficicnt to increase AE to a value greater than'at' least 0.2 volt, and physically developing the latent contrast by'then applying to said layer a developing solution containing a salt of a metal higher than copper in the electromotive series and reducible to metal in solution andawater-solublc reducing agent.
• a method of producing photographic. contrasts comprising the steps, selectively exposing slayer having a pH less than about-10am containinga light sensitive diazoni m mpo nd tel-d composesaid compoun t lected portions of thelayer, said layerafter exposure hav?
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7.0 and containing a light sensitive thiazine compound to decompose said compound at selected portions of the layer, said layer after exposure having a AB, in the presence of a water-soluble silver salt, of less than 0.8 volt, treating the exposed layer withan alkaline medium and moisture in the presence of said water-soluble silver salt to form a latent silver contrast, the alkalinity of the alkaline medium being sufficient to increase AE to a vaue greater than at least 0.2 volt, and physically developing the latent contrast by then applying to said layer a developing solution containing a salt of a metal higher than copper in the electromotive series and reducible to metal in solution and a water-soluble-reducing agent.
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7.0 and containing a light sensitive indamine to decompose said compound at selected portions of the layer, said layer after exposure having a AB, in the presence of a water-soluble silver salt, of less than 0.8 volt, treating the exposed layer with an alkaline medium and moisture in the presence of said water-soluble silver salt to form a latent silver contrast, the alkalinity of the alkaline medium being sufficient to increase AB to a value greater than at least 0.2 volt, and physically developing the latent contrast by then applying to said layer a developing solution containing a salt of a metal higher than copper in said electromotive series and reducible to metal in solution and a water-soluble reducing agent.
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7.0 and containing a light sensitive azine compound to decompose said compound at selected portions of the layer, said layer after exposure having a N5, in the presence of a water-soluble silver salt, of less than 0.8 volt, treating the exposed layer with an alkaline medium and moisture in the presence of said water-soluv ble silver salt to form a latent silver contrast, the alkalinity of the alkaline medium being sufficient to in: crease AE to a. value greater than at least 0.2 volt, and physically developing the latent contrast by then applying to said layer a developing solution containing a salt of a metal higher than copper in the electromotive series and reducible to metal in solution and a water-soluble 'reducing agent.
• a method of producing photographic contrasts comprising the steps, selectively exposing a layer having a pH less than about 7.0 and containing a light sensitive compound selected from the group consisting of diazonium, azine, oxazine, thiazine and indigo compounds, indophenols, indamines, andindanilines, to decompose said compound at selected portions of the layer, said layer after exposure having a AB, in the presence of a watersoluble silver salt, of less than 0.8 volt, treating theex posed layer with an aqueous solution of an alkali metal thiosulfate in the presence of said water-soluble silver salt to form a latent silver contrast, the alkalinity of the thiosulfate solution being sufficient to increase AB to a value greater than at least 0.2 volt, and physically developing the latent contrast by then applying to said layer a developing solution containing a salt of a metal higher than copper in the electromotive series and reducible to metal in solution and

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• Silver Salt Photography Or Processing Solution Therefor (AREA)
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  • BE BE504812D patent/BE504812A/xx unknown
• 1943
  • 1943-05-08 DE DED4051D patent/DE892586C/de not_active Expired
• 1950
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• 1951
  • 1951-07-10 US US236068A patent/US2738272A/en not_active Expired - Lifetime
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  • 1951-07-22 DE DEN4202A patent/DE892553C/de not_active Expired
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• 1956
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