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
  • G03C1/00—Photosensitive materials
  • G03C1/494—Silver salt compositions other than silver halide emulsions; Photothermographic systems ; Thermographic systems using noble metal compounds
  • G03C1/496—Binder-free compositions, e.g. evaporated
  • G03C1/4965—Binder-free compositions, e.g. evaporated evaporated
• • 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
  • Y10S430/133—Binder-free emulsion

Definitions

• This invention relates to photography and more particularly to novel sensitized photographic media and process for preparing same.
• Photographic media formed of a substantially homogenous mass of contiguous microcrystals of silver halide in a binder-free layer on a suitable substrate, and a process for manufacturing such media by vacuum evaporation techniques are disclosed in French Patent No. 1,267,623, granted June 12, 1961, to Technical Operations, Incorporated.
• Media of this type can be distinguished from conventional emulsion type photographic film and other photographic media not only by their structure and method of manufacture, but also for some purposes by their high acutance, high resolution and quick developability.
• Such media generally exhibit native sensitivities, in terms of ASA speed ratings, for example in about the range of 1X10 to l l0
• Such media may be photographically sensitized by treatment of the open surface of the microcrystalline layer, i.e. the surface of the layer which is not contiguous with the substrate.
• sensitivity of such media is enhanced by such treatment of the open surface of the silver halide layer
• certain problems arise.
• the optical sensitizer and chemical sensitizer are generally antagonistic. Consequently, either sensitivity to white light is reduced, or optical sensitization is poorly, if at all, achieved.
• some chemical sensitization procedures are not compatible with other treatments. For instance, surface sensitization can be achieved by depositing a sensitizer material, such as an elemental metal, upon the open surface of the microcrystalline silver halide layer.
• the present invention is directed toward the sensitization of mircocrysalline, binder-free, photographic media and has for its principal object the provision of a novel method for sensitizing media of this type and the products of such method.
• a sensitized photographic medium comprising a microcrystalline, binder-free layer of silver halide deposited on a surface of a support element and having a sensitivity stratum disposed at the interface of said layer and said surface;
• sensitization can be achieved by treatment with two or more sensitizers or sensitizing methods, at least one of which is antagonistic to the other or others when applied to the same surface of such a medium;
• the invention ac cordingly comprises the processes involving the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products and compositions possessing the features, properties and relation of elements which are exemplified in the following detailed disclosure and the scope of the application all of which will be indicated in the claims.
• the present invention is intended to provide a substrate mounted microcrystalline, binder-free, silver halide photographic layer which is sensitized at the layer-substrate interface. Additionally such a medium is therefore sensitizable at the open surface of the layer by yet one or more other sensitizing procedures and materials without antagonistic effect between the sensitizers. Generally, the formation of such a medium is achieved by providing the usual photographically inert substrate, or support sheet, and distributing upon one surface thereof a material which will sensitize, either optically or chemically, a microcrystalline binder-free silver halide layer.
• the latter is then formed, as by vacuum evaporative techniques, by deposition of the microcrystals in a substantially homogenous binder-free stratum on top of the substrate surface hearing the sensitizer.
• This creates, at least adjacent the interface of the substrate surface and the binder-free stratum, an image-forming sensitivity stratum, ie a stratum which enhances the image-forming characteristics of the silver halide.
• the foregoing process provides a novel and basic photographic medium which possesses several advantages. For instance, Where sensitizing materials are deposited, for example as a stratum, upon the outer or open surface of a binder-free microcrystalline silver halide layer, the thickness of such a sensitizer stratum renders it susceptible to mechanical damages. Further, when such a stratum is exposed to the ambient atmosphere, it is equally susceptible to contamination by or chemical reaction with airborne substances. In either instance, the sensitization achieved may then be impaired.
• the structure of the basic medium formed by the process of the present invention provides greater stability toward mechanical and chemical disturbance inasmuch as the sensitivity stratum lies in a protected position between the substrate and the silver halide layer.
• the basic photographic medium of the present invention may also be readily modified to provide some unique effects. Because of the positioning of the sensitivity stratum, provided by a first sensitizing material, between the substrate and the silver halide layer, the outer or open surface of the latter can additionally be sensitized Without materially affecting the sensitization previously achieved. Thus, a large variety of combination sensitizations can be produced.
• control of the thickness of the silver halide layer also yields some significant modifications. It is desired to keep the silver halide within a thickness range of about 0.1 to 0.5 micron inasmuch as the optimum photographic parameters such as gamma, density and sensitivity, are found within this range. Thin layers such as 0.1 micron to 0.2 micron are preferred in some modifications of the invention and thicker layers, e.g. 0.2 to 0.5 micron are desirable in other modifications for reasons pointed out hereinafter.
• the sensitization achieved by depositing a first sensitizer onto the substrate and subsequently depositing a contiguous microcrystalline layer of silver halide over the sensitizer is believed to be a surface effect.
• the sensitivity stratum is believed to be confined to the interface between the substrate and the silver halide and probably does not extend more than a fraction of a micron (less than 0.1 micron) into the silver halide layer depending upon the smoothness of the substrate surface.
• the silver halide layer is relatively thick, e.g. about 0.5 micron, it is then apparent that the surface sensitization of the silver halide substrate interface will not increase the sensitivity of the medium with respect to the outer surface of the silver halide layer.
• the present invention contemplates a modification of the basic photographic medium in which diverse sensitizers are respectively applied to opposite surfaces of the microcrystalline silver halide layer.
• Binder-free microcrystalline silver halide layers can be chemically sensitized to provide two different types of media, one of which is normally developable to provide a positive image, and the other of which is similarly developable but provides a negative image.
• a sensitizing stratum between a silver halide layer of predetermined thickness and the substrate By providing a sensitizing stratum between a silver halide layer of predetermined thickness and the substrate, and then treating the open surface of the layer with the same or another sensitizer, one obtains a photographic medium which has quite unusual properties.
• a medium if exposed to form a latent image and then developed at the open surface with a developing agent that does not materially dissolve the silver halide, will yield a developed surface image of one type.
• Such surface silver images are amenable to transfer from the silver halide layer to a receiving sheet by adhesion. This transfer may be readily effected because the adhesion between the developed silver and the underlying undissolved silver halide is quite poor.
• the surface silver image at the second sensitized surface may be removed by transfer, may be destroyed by mechanical abrasion for example, or may be removed by the use of an oxidative etch such as a solution of potassium dichromate.
• an oxidative etch such as a solution of potassium dichromate.
• the medium is sufliciently thick e.g.
• the medium may now be further developed in a developing reagent, such as an internal developer which contains for example a quantity of silver halide solvent, to remove silver halide overlying the sensitivity stratum so that the latent image at or adjacent the latter can be developedinto a silver image of, if desired, the other type.
• a developing reagent such as an internal developer which contains for example a quantity of silver halide solvent
• a positive image may be obtained at the outer sensitized surface which image is then transferrable to an opaque reflective transfer sheet to provide a positive reflection print.
• the image formed at the silver halide-substrate interface can be also a positive.
• both a positive transparency and a positive reflection print can be formed from the same medium.
• the basic medium heretofore disclosed is again sensitized on its outer surface to provide a dual sensitization.
• the two sensitizers differ in that one is a chemical sensitizer which increases the sensitivity of the medium to white light, while the other is an optical sensitizer which extends the useful range of the medium in terms of frequency response.
• the silver halide layer be sufficiently thin (e.g. about 0.1 to 0.2 micron) so that while the two sensitizations do not chemically interact with one another, the medium can be developed as by an internal developer to provide a single image adhering to the substrate.
• the sensitivity stratum can be formed by depositing the sensitizing material upon the substrate as by precipitation from solution
• the sensitization of the outer surface of the silver halide layer can be achieved in a variety of ways, for instance by a third evaporation deposition, by deposit from solution, by treatment with sensitizing solutions, and other like techniques.
• Typical photographic media according to the present invention may be prepared by vacuum evaporation techniques similar to those described in the aforementioned French Patent No. 1,267,623.
• a basic machine of the kind useful in applying such techniques to form media of the present invention is illustrated and described in the book Vacuum Deposition of Thin Films by L. Holland, published by John Wiley & Sons, New York City, 1948, pp. 7-8.
• Vacuum coating apparatus of this type is well known and usually comprises an evacuatable container, such as a bell jar, and known means for evacuating the latter to a predetermined and controlled ambient. pressure which is preferably less than 1 l0- mm. of Hg. The latter appears to be the maximum pressure at which reasonably desirable film formation from silver halides can be achieved.
• a crucible or boat which is intended to carry the material which is to be evaporated.
• Means for heating the boat are usually included, and in one form of the apparatus the boat is made of, for instance, tungsten provided with leads to a source of electrical power so that the crucible can be heated electrically. By this method the temperature of the evaporating material can be readily controlled.
• the starting material may be heated by electrical induction, for example.
• the apparatus also includes means for holding substrate material, such as a support sheet, at a predetermined location spaced from the boat within the bell jar wherein preferably one surface of the substrate faces the boat, thus insuring that the stream of vapor from the evaporating material in the boat will strike the substrate surface and condense thereon to form a film or layer according to the well-known principles of evaporation techniques.
• a quantity of evaporable sensitizer is placed within the container, for example, at a first location and a suitable substrate sheet is placed Within the container at a second location displaced a predetermined distance from the first location.
• the container is pumped down to achieve an operating pressure, and the sensitizing material brought to a temperature at which evaporation thereof will occur.
• the resulting vapor will transfer to and be deposited upon the substrate surface and can readily be controlled to provide a layer of substantially uniform thickness.
• concentration of material so deposited is determined according to such factors as the heated sensitizers vapor pressure which is temperature dependent, and the time during which evaporation occurs.
• the substrate may be coated in either batch or continuous manner by this technique or by other techniques such as precipitation from solution.
• a microcrystalline binder-free silver halide layer of predetermined thickness is then deposited thereon. This may be accomplished in the same apparatus, for instance, by leaving the sensitizer-coated substrate in its position, replacing the container of sensitizer with a container of silver halide, again pumping down the operating pressure, and raising the silver halide to an evaporation temperature.
• the sensitized coated substrate in strip form can be continuously transported out of the evaporative stream of sensitizer and through another position within the same ambient reduced pressure.
• the thickness of the silver halide layer is readily controlled as by adjustment of the evaporation temperature, the evaporation time (in batch processing) or speed of movement of the substrate (in continuous processing), and the distance between the silver halide source and substrate, or any of them.
• the layer thus provided exhibits a density which appears quite close, i.e. within about to that of a solid silver halide crystal. As taught by the aforesaid French patent, the density ratio of polymicrocrystalline layers of this type to solid crystals is approximately 95%.
• Exemplary support or substrate materials upon which the doped layer is deposited include many diverse materials, either moisture impervious and pervious, e.g. vitreous substances such as glass; fibrous materials such as paper and composition board; natural polymers such as gelatin; synthetic resins including particularly polyethylene terephthalate, polyvinyl chloride, copolymers of vinyl acetate-vinyl chlorides, polystyrene and many other polyesters, polyamides and the like; and cellulose esters such as cellulose acetate, cellulose propionate and the like.
• microcrystalline binderfree silver halide materials which can be evaporated onto a surface to provide a sensitization of the microcrystalline binderfree silver halide are the normally (i.e. under standard conditions of temperature and pressure) solid elements other than the halogens, selected from the group of elements of the periodic table classified in Groups I through VI and VIII.
• chemical elements which can be vapor deposited on the outer surface of a micro- 5 crystalline, binder-free silver halide photographic medium to increase the photographic sensitivity thereof, and with which, in each case, there can be obtained upon standard exposure and development a normal (i.e. a negative) image, a solarized (i.e. direct positive) image or both, are set forth in tabular form in Table I following.
• the layer of sensitizer material is not substantially greater than 10 atoms per square centimeter of adjacent surface of the photographic silver halide.
• Solarized images are generally achieved Where the concentration of sensitizer is between approximately 10 to 10 atoms per square centimeter of adjacent silver halide surface. Layers in yet heavier concentration result in fogging.
• the last three columns set forth the approximate pressure in millimeters of mercury, time used for achieving appropriate deposition of the sensitizer vapor, and either the voltage or current through a crucible, at which volt age or current, satisfactory vapor deposition of the element is obtained.
• the filament used in most cases in Table I is tungsten and has approximate dimensions of 0.75 x 2.25 X 0.002 inch.
• a tantalum filament or other filament material is preferably employed to avoid having a filament with which the starting material reacts chemically.
• positing antimony and bismuth a tantalum filament is preferred.
• the teachings of Holland at pages 110-114 in his aforesaid book can be followed in many cases, particularly in the use of a boat form of filament.
• the media sensitized to . provide normal images, upon exposures of relatively short duration, for example second, and subsequent development will of course yield negative images.
• the elements of the above table are also effective as sensitizers although the use of the ammonium chloroiridite solution is often precluded.
• certain of the elements such as chromium, selenium and sulfur, display a strong tendency to yield a solarized image even when treated with the solution.
• Their usage to provide negative-image forming sensitization by deposit on the substrate is not recommended unless the substrate is pervious to the solution and the silver halide substrate outerface can thus be treated.
• Deposition of elemental materials can also be achieved from solution. This is of particular value in such cases as the use of sulphur and selenium because these latter are difficult to control in a vapor deposition process owing to their relatively high vapor pressures at relatively low temperatures.
• a layer of sulphur for instance, can be deposited from solution using a colloidal suspension of sulphur in dioxane, a quick evaporation vehicle identified in the Merck Index, 7th edition, page 387, published 1960 by Merck & Co., Inc. of New Jersey.
• Selenium and sulphur can be deposited, each from a solution in dimethyl sulfoxide (Merck Index, ibid., page 373). In each latter case a saturated solution is employed at room temperature, and the precipitant is washed with water with which dimethyl sulfoxide is miscible and in which the precipitant is relatively insoluble.
• sensitizier is to be applied to either the substrate or silver halide layer open surface by other than an evaporative process
• a wide variety of sensitizers is available for use, for instance, a host of dyes in aqueous or aqueous-alcohol solutions for optical sensitization, and many diverse chemically sensitizing materials. Included in the latter are organic compounds such as condensation products of alkylene oxides, various polyamines, polyvinyl resins, sulfoxides, complexed borane hydrides and many others.
• useful chemical sensitizers are inorganic compounds such as copper halides, ammonium halides and acetate, salts providing hydroxyl ions in solution and many others.
• the internal developer employed is formed from 60 ml. of the foregoing surface developer to which 3 ml. of 1% sodium thiosulfate solution is added.
• EXAMPLE 1 A sheet of subbed polyethylene terephthalate available commercially under the trademark Cronar from E. I. du Pont de Nemours & Co., Delaware, and in which the substratum is believed to be a water permeable colloid layer (described in US. patents, No. 2,627,088 or No. 2,698,242) is placed in a vacuum deposition apparatus of the type described at a distance of approximately 4 inches from a tungsten container having dimensions of approximately 0.75 x 2.25" x 0.002". A sample of less than 10 milligrams of gold is placed in the container. The apparatus is pumped down to achieve an operating pressure of approximately 2X10 mm.
• the tungsten container is heated by application therethrough of 2 amperes at 110 volts. After the gold is melted, the substrate is exposed to the vapor stream therefrom for a period of 5 seconds. This forms a layer of about 10 or slightly less (i.e. within one order of magnitude) atoms per square centimeter of the surface of the sheet.
• a new container of similar size is substituted for the first container and a sample of silver bromide of high purity, i.e. less than ppm. impuri ties, placed in the new container.
• the apparatus is again pumped down to achieve an operating pressure of approximately 1X10 mm. of mercury and the container raised to a temperature (about 625 C.) at which the silver halide is molten. Under these conditions, the process is carried on for about one minute to evaporate the silver halide and condense the vapors thereof as a substantially homogeneous layer of contiguous microcrystals of binder-free silver bromide until the layer is of substantially uniform thickness of about 0.3 micron.
• EXAMPLE 2 A gold sensitized basic photographic medium is prepared according to Example 1. However, the silver halide outer surface thereof is sensitized by application in the evaporator apparatus of another layer of gold deposited in an apparatus of another layer of gold deposited in an increased time (about 5.3 sec.) to achieve a concentration of between and 10 atoms per square centimeter of the silver halide surface on which it is deposited. The medium thus formed is exposed and then developed with a surface developer for seconds. This forms a surface silver image on the surface of the silver halide layer sensitized with the second deposit of gold. The surface developed medium is then washed with water and dried.
• a tacky transfer medium such as a pressure-sensitive adhesive coated polymeric sheet (available for example as Scotch brand tape manufactured by Minnesota Mining and Manufacturing Co.) to the silver image and stripping the tape from the medium the surface silver image is substantially completely removed leaving the medium substantially silver image free.
• 21 second silver image is formed at approximately the location of the first sensitized surface of the silver halide layer. Because of the disparity in the concentrations at the two silver halide surfaces the first silver image removed with the transfer sheet is a positive image, while the second formed silver image is a negative image which adheres well to the support sheet.
• EXAMPLE 3 A gold sensitized basic photographic medium is prepared according to Example 1. However, the evaporation time with respect to the silver bromide is reduced to achieve a microcrystalline binder-free silver halide layer of approximately 0.2 microns. A sample of about 5 mg. of l,1-diethyl 2,2'-carbocyanine bromide (pinacyanol) is sublimated at a 20 pressure at a temperature of approximately 200 C. onto the open silver bromide surface of the basic medium. The evaporation is continued until there is a substantially uniform distribution of a visible layer of dye on the silver bromide surface in a concentration of about 1 microgram per 70 sq. mm.
• pinacyanol l,1-diethyl 2,2'-carbocyanine bromide
• the film upon wetting the dye surface of such a medium with pure water, upon the same exposure and development the film shows a red sensitivity of the order of 4 l0 and a white light sensitivity of about 4X 10*.
• the basic medium when sensitized by application of dye to its surface, upon similar exposure and development shows a minimum sensitivity to the white light of more than 4X 10 with no impairment of the previously mentioned red sensitivity.
• An image recording medium comprising a substrate element having a surface providing a recording area, a photographic layer of vapor deposited photosensitive silver halide microcrystals in substantially continuous phase supported upon said element and substantially covering the extent of said area, said layer being adhered directly to said substrate and said microcrystals being cohered directly to each other, said layer having a density less than that of said halide in solid crystalline form, said layer being a fraction of a micron in thickness and the surface portion of said layer over said area immediately adjacent the substrate element having been treated with a sensitizing material to provide an increased photographic sensitivity for said surface portion.
• a silver halide photographic element comprising a substrate sheet having a surface providing a recording area, and a photoresponsive layer having a stratum of substantially binder-free, vapor deposited silver halide microcrystals supported on said surface of said sheet and substantially covering said area of said sheet, said stratum having a thickness of a fraction of 21 micron and a density of less than that of said halide in solid crystalline form, said layer further including a photosensitizer for said halide applied and distributed substantially uniformly over the surface of said stratum over said area immediately adjacent the substrate sheet.
• a method of forming a silver halide photographic element comprising evaporating silver halide under a high vacuum with said silver halide at a temperature in excess of its melting point, condensing the silver halide vapors over a surface area of a base member to form a layer of light responsive silver halide upon said base as a support therefor, said evaporation being conducted from a pool of molten silver halide, said evaporation and condensation being effected under substantially stable conditions of pressure and temperature to afford substantially uniform characteristics to the silver halide deposit, and wherein said silver halide is deposited to a thickness sufficient to cover substantially said entire area of said base member but no greater than a fraction of a micron, and said method further including the application of a silver halide photosensitizer to the surface of said silver halide layer immediately adjacent the base member.
• a method of forming a photographic medium comprising the steps of distributing a first photosensitizing material for silver halide onto a substrate surface and condensing a substantially homogeneous mass of contiguous unichrocrystals of silver halide from the vapor state thereof in a substantially uniform binder-free layer overlying said material, and treating the surface of said layer remote from said substrate with a silver halide photosensitizing material, (a) the first mentioned photosensitizing material and its concentration in terms of quantity per unit area of silver halide surface, and (b) the second mentioned photosensitizing material and the treatment therewith, each of (a) and (b) improving the image producing qualities of said silver halide over its unsensitized state relative to speed, or spectral sensitivity, or ability to produce a solarized image.
• a method of forming a photographic medium comprising the steps of condensing a substantially uniform stratum of a normally solid, photosensitizing material for silver halide from the vapor state thereof onto a substrate, and condensing a substantially homogeneous mass of contiguous microcrystals of silver halide from the vapor state thereof in a substantially uniform binder-free layer overlying said material, and treating the surface of said layer remote from said substrate with a silver halide photosensitizing material, (a) the first mentioned photosensitizing material and its concentration in terms of quantity per unit area of silver halide surface, and (b) the second mentioned photosensitizing material and the treatment therewith, each of (a) and (b) improving the image producing qualities of said silver halide over its unsensitized state relative to speed, or spectral sensitivity, or ability to produce a solarized image.
• a method of forming a photographic medium comprising the steps of condensing a substantially uniformly distributed quantity of a normally solid first photosensitizing material for silver halide from the vapor state thereof onto a substrate, condensing a substantially homogeneous mass of contiguous microcrystals of silver halide from the vapor state thereof in a substantially uniform binder-free layer overlying said material, and treating the surface of said layer remote from said substrate with a silver halide photosensitizing material, (a) the first mentioned photosensitizing material and its concentration in terms of quantity per unit area of silver halide surface, and (b) the second mentioned photosensitizing material and the treatment therewith, each of (a) and (b) improving the image producing qualities of said silver halide over its unsensitized state relative to speed, or spectral sensitivity, or ability to produce a solarized image.
• one of said first and second sensitizing materials is an optical sensitizer, and the other of said first and second sensitizing materials is a chemical sensitizer.
• one of said first and second sensitizing materials is a material for so sensitizing the adjacent surface of said layer as to provide said surface with the capability of having a latent image thereat normally developable into a direct positive image
• the other of said materials being a material for so sensitizing the surface of said layer adjacent thereto as to provide the latter surface with the capability of having a latent image thereat normally developable into a negative image
• a photographic medium comprising a substrate, first photosensitizing material for silver halide distributed on a surface of said substrate, a homogeneous mass of vapor deposited contiguous microcrystals of silver halide in a binder-free layer in contact with and overlying said first sensitizing material, and second photosensitizing material for silver halide 0n the open surface of said layer, the concentrations of both sensitizing materials in terms of quantity per unit area of silver halide surface being selected to improve the image producing qualities of said silver halide over its unsensitized state relative to speed, or spectral sensitivity, or ability to produce a solarized image.
• a photographic medium as defined in claim 24 wherein said silver halide is selected from the group consisting of silver bromide, silver iodide, and silver iodobromide.
• a photographic medium as defined in claim 28 wherein said silver halide is selected from the group consisting of silver bromide, silver iodide, and silver iodobromide.
• a photographic method of forming multiple images comprising the steps of forming a photographic medium by distributing a substantially uniform stratum of first chemical sensitizing material onto a substrate, condensing a substantially homogeneous mass of contiguous microcrystals of silver halide from the vapor state thereof in a substantially uniform binder-free layer overlying said stratum, treating the open surface of said layer with a second chemical sensitizing material, exposing said medium to form a developable latent image therein, developing with a surface developer the sensitized open surface of said layer to form a surface silver image, transferring substantially all of said surface image by adhesion to a transfer sheet to leave said medium substantially free of silver image, and developing said medium with a developer containing a silver-halide solvent to form a second silver image at the surface of said layer previously sensitized with said first material.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)

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Citations (2)

• 0
  • NL NL301545D patent/NL301545A/xx unknown
• 1962
  • 1962-12-11 US US243746A patent/US3219449A/en not_active Expired - Lifetime
• 1963
  • 1963-12-09 BE BE641008A patent/BE641008A/xx unknown
  • 1963-12-11 GB GB49026/63A patent/GB1072686A/en not_active Expired

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