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
  • G03C8/24—Photosensitive materials characterised by the image-receiving section
  • G03C8/26—Image-receiving layers
  • G03C8/28—Image-receiving layers containing development nuclei or compounds forming such nuclei

Definitions

• This invention relates to the production of transfer images by the silver salt diffusion process.
• This dissolved silver halide diffuses to a transfer layer, where it is reduced to a positive image by the developer under the catalytic action of the nuclei for development present in the said layer.
• the meaning of the terms negative and positive as used in this description is relative, which means that if the emulsion layer is exposed to a negative original, a direct negative will be produced in the reception layer whereas if the emulsion layer is exposed to a positive original a direct positive will be obtained in the said transfer layer.
• a photographic element comprising a silver halide emulsion layer and having coated thereon a gelatin or polyvinyl alcohol layer containing physical development nuclei, for example colloidal silver or chemical precipitants for silver ions. If this element is treated after exposure with a silver halide developer containing a silver halide solvent, there is obtained in the silver halide emulsion (negative) layer a negative silver image and in the upper layer a positive silver image of the copied original.
• the upper layer is then transferred in several continuous portions onto absorbent supports to produce several positives. It is, however, in many cases diflicult to detach the positive layer in several strata from the negative layer due to the strong cohesion of the former as a result of which this layer tends to be completely detached from the negative layer with the first print.
• binding agents are used for the positive layer which possess only a comparatively weak cohesion and to which are added organic compounds that do not form continuous films and which are readily soluble in Water and alkalis. In this way, positive layers are obtained which can easily be pulled off in several thin successive strata.
• binding agents there may be employed watersoluble starch ethers or carboxymethyl cellulose. Suitable starch ethers are the methyl, ethyl, and starch ethers containing per anhydroglucose unit a carboxymethoxy o-cH,cooH
• polyethylene glycols having a molecular weight of about 200 to 2000 are particularly suitable organic compounds having no film-forming capacity. These polyethylene glycols substantially facilitate the layer being printed olf in thin portions and are unable to penetrate to an appreciable degree into the negative layer. They are preferably used in amounts of 10-70 percent by weight as calculated on the total amount of binding agent plus polyethylene glycol.
• a salt-containing solution such as a silver halide developer solution
• colloidal heavy metals such as colloidal silver, heavy metal sulphides or heavy metal selenides such as silver, lead, zinc, and cadmium sulfides
• colloidal heavy metals such as colloidal silver, heavy metal sulphides or heavy metal selenides such as silver, lead, zinc, and cadmium sulfides
• these layers compounds such as heterocyclic nitrogensulphur compounds, for example 5-phenylmercaptotetrazole, which on the one hand lead to a black form of silver deposit and on the other hand produce pure whites.
• the material after exposure of the negative layer, the material may be conducted through a silver halide developer solution containing a silver halide solvent.
• the developer and the silver halide solvent for example sodium, potassium, or ammonium thiosulfate, penetrate through the positive layer into the negative layer.
• the exposed silver halide is developed and the unexposed silver halide is dissolved.
• the dissolved silver halide diffuses into the positive layer and forms therein the positive of the copied original.
• a sheet of ordinary writing paper is placed on the positive layer, which is still in close contact with the negative layer, and these combined sheets are passed through a tray or tank of water.
• the excess water is squeezed out by a roller wringer or by a pair of rollers and the writing paper is separated from the positive layer.
• the positive layer can be detached as a single layer if it is from '1 to 3 microns thick. With greater layer thicknesses, for example of from 5 to 15 microns, a larger number of layers or strata can be detached.
• the process can be repeated several times until the entire positive layer has been removed from the negative layer. In this way, several positive prints are obtained from one negative.
• layers which contain a comparatively large quantity of polyethylene glycol, they soften very considerably in a developer which contains a salt.
• the positive layer can then be transferred from the negative layer to another support during development, either all at once or stratum by stratum.
• the positive layer of the two-layer material can be transferred to another support, for example to a support consisting of normal writing paper, in the manner described above and either all at once or stratum by stratum. If it is desired to produce a large number of prints from the negative-positive layer system, it is advisable to apply the positive layer in two separate working steps, for example, by choosing as bottom layer a material which swells to a lesser degree in water than the upper layer.
• the silver content of the negative layer may be varied according to the other conditions which are chosen. Layers containing less than 1 g. of silver per square meter usually only produce from 2 to 3 positives, whereas layers containing from 3 to 4 g. of silver produce substantially more positives.
• Hardened gelatin is generally employed as binding agent for the negative layer.
• Substances which facilitate detachment of the positive layer such as an emulsion of stearic acid, may be added to the gelatin layer if desired.
• the sharpness of the positives obtained is satisfactory, the positives being sharper the further they are removed from the negative layer when they are formed.
• the precipitation of the dissolved silver salts on the development nuclei requires a certain high silver salt concentration the range of which is always narrower with increasing distance from the negative because of a lateral diffusion.
• a white (i.e. unexposed) line in the negative produces a line which becomes progressively thinner as the positive is formed further from the negative, which is recorded by the eye as an increase in sharpness. It has also been found that the silver precipitation in the positive layer occurs quite uniformly throughout the entire cross section of the layer if the choice and quantity of the nuclei are correctly measured.
• Example 1 100 cc. of a 5 percent stearic acid emulsion are added to a liter of an ordinary silver chloride emulsion together with clarifying, hardening and wetting agents. This emulsion is used to form a negative layer containing 1.5 g. of silver per square meter.
• a positive layer is coated on to the negative layer.
• the positive layer is cast from a solution having the following composition:
• the two-layer material after being exposed to the original to be reproduced is first passed by itself through the developer solution.
• a sheet of typewriting paper is then laid on the positive layer, whereafter the material while in contact with the said paper is passed through the apparatus once more. Then typewriting paper is then separated from the two-layer material.
• a major part of the positive layer remains adhered to the typewriting paper. By repeating the operation, 2 to 3 more positive copies can be produced.
• Example 2 An ordinary gelatino silver chloride emulsion containing a stabilizer, such as benzotriazole in usual amounts, is cast onto a paper or film support to produce an emulsion layer containing 2.5 g. of silver per square meter.
• a stabilizer such as benzotriazole in usual amounts
• econd layer is applied to the aforementioned layer.
• the second layer is cast from a solution having the following composition:
• the thickness of the layer should be 12 microns when dry.
• this 2-layer material is developed at room temperature for about 1 minute in a developer having the composition:
• This latter layer is cast from a solution having the following composition:
• Detachment of the positive layer stratum by stratum from the negative layer is effected in this case by means of water.
• a sheet of writing paper is placed on the twolayer material and the sheets are passed in contact through a tray or tank of water the excess water being squeezed out by rollers.
• the Writing paper is detached from the two-layer'material and it is seen that the uppermost part of the positive layer adheres to the writing paper. This operation can be repeated about times, that is to say, about 10 positive prints can be obtained from one negative.
• a process for the production of photographic transfer images by the silver salt diifusion process which comprises exposing a photographic sheet material having a light-sensitive silver halide emulsion layer and coated thereon an unsensitized colloid layer, the colloid of which consists essentially of a member of the group consisting of a water-soluble starch ether and carboxymethyl cellulose, said colloid layer having incorporated therein a polyethylene glycol and physical development nuclei, developing the said exposed photographic material in a silver halide developing solution in the presence of a silver halide solvent to produce a negative silver image in the said silver halide emulsion layer and a positive silver image in the said colloid layer, and transferring at least a stratum of the said colloid layer containing the said positive silver image onto a separate support.

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Citations (7)

• 0
  • BE BE586259D patent/BE586259A/xx unknown
• 1959
  • 1959-01-08 DE DEA31092A patent/DE1076491B/de active Pending
• 1960
  • 1960-01-05 US US512A patent/US3067033A/en not_active Expired - Lifetime
  • 1960-01-05 CH CH7460A patent/CH405928A/de unknown
  • 1960-01-06 FR FR814925A patent/FR1244254A/fr not_active Expired
  • 1960-01-07 GB GB627/60A patent/GB925313A/en not_active Expired

Patent Citations (7)

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