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
• • 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
  • Y10S430/136—Coating process making radiation sensitive element

Definitions

• This invention relates to photography and more particularly to photographic elements having, as the lightsensitive component, a substantially binder-free layer of silver halide crystals and to a process for preparing both such elements and additional elements utilizing a hydrophilic colloid binder.
• Conventional photographic elements employ a support material coated with a photographic emulsion that typically includes photosensitive silver halide crystals dispersed in a hydrophilic colloid such as gelatin.
• a hydrophilic colloid such as gelatin.
• gelatin or another hydrophilic colloid is a desirable, and necessary constituent of a photographic element.
• Typical binder colloids absorb light of short wavelengths (e.g. ultraviolet rays); as such, the binder material can determine the short wavelength limit of usefulness for any given photographic element.
• Such a condition operates to impede preparation of high quality, ultraviolet-sensitive photographic elements such as those used in astronomical studies and as electron-recording elements.
• developing agents are required to penetrate the colloid in order to develop a photographic image on the photosensitive material.
• the hydrophilic colloid tends to attract moisture which can adversely affect the stability and image-producing capability of the photographic element, and special measures must be taken to ensure adequate adhesion between the normally hydrophobic support and the hydrophilic colloid binder.
• Such coating means requires specialized apparatus to carry out the coating operation in a sealed system under conditions of elevated temperature and reduced pressure.
• the binderless, microcrystalline silver halide layers so deposited are subject both to non-uniform photographic response and to deterioration upon storage, the deterioration generally resulting from such factors as pressure-caused abrasion fog.
• presently known binderless silver halide elements are amenable to spectral sensitization only subsequent to the coating operation.
• Another object of this invention is to provide novel, substantially binder-free photographic elements employing preformed, presensitized silver salt crystals.
• Another object of the present invention is to provide a novel electrostatic coating process for preparing both substantially binder-free silver salt photographic elements and photographic elements incorporating a hydrophilic colloid.
• the objects of the present invention are accomplished both with photographic elements having an electrically insulating support coated with a substantially binder-free, radiation-sensitive layer of preformed silver salt crystals and with an electrostatic coating process for preparing both the subject elements and elements containing a hydrophilic colloid, which process includes:
• radiation-sensitive is descriptive of a chemical species (silver salts) that are activated by exposure to electromagnetic radiation to typically provide latent images that can be intensified by various photographic development techniques to provide visible images.
• the subject silver salt crystals are radiation-sensitive species that are light-sensitive.
• radiationsensitive comprehends responsiveness to activating radiation both within and without the visible portion of the spectrum.
• radiation-sensitive refers to the responsiveness of an activatable chemical species to a wide segment of electromagnetic radiation including, for example, X-radiation, ultraviolet rays, infrared radiation and the like.
• the preformed, radiation-sensitive silver salt crystals used in the practice of this invention include those of the silver halides typically employed in gelatino-silver halide photographic emulsions, such as silver bromide, silver chloride and silver iodide. Additionally, mixtures of these halides are advantageously utilized, as are silver halide co-crystals such as, for example, silver bromoiodide, silver chlorobromide, silver chloroiodide, and the like silver halides.
• the silver halides that function advantageously in the practice of this invention include sensitized preformed silver halide crystals that have been spectrally sensitized to additional portions of the spectrum, conventionally with sensitizing dyes such as cyanine dyes, carbocyanine and the like polymethine cyanine dyes, merocyanine dyes, styryl dyes, oxonol dyes, as well as additional sensitizers like substituted polycyclic quinones, pyrylium compounds and the like. Still additional spectral sensitizers are well known in the art.
• Spectrally sensitized silver halides can be dispersed in combination to obtain a composite dispersion containing silver salts sensitized to record various portions of the spectrum via the use of sensitizing dyes.
• sensitization can be effected subsequent to preparing a photographic element, such as by bathing the element in a solution of sensitizing dye.
• the silver salt crystals useful herein include silver salts of sensitizing dyes, they generally being the complex reaction product of a water soluble silver salt and a spectral sensitizing dye.
• Particularly advantageous silver salts include those of the more highly solubilizing anions, and especially silver nitrate.
• the complexes are sensitive in general to the absorption spectra of the complexed sensitizing dye.
• the resultant preformed silverdye complex crystals are desirably dispersed in a hydrophilic colloid material prior to being coated on a support material.
• Useful spectral sensitizing dyes include, for example, dyes of the types commonly used to spectrally sensitize photographic silver halides and include such organic dyes as cyanine dyes, merocyanine dyes, oxonol dyes, hemicyanine dyes, styryl dyes, hemioxonol dyes, benzylidene dyes and the like. Such spectral sensitizers enter into complexes of varying strength with soluble silver salts.
• Preferred spectral sensitizing dyes used to prepare silver-dye complexes are merocyanine dyes such as:
• These silver-dye complexes are conveniently prepared by mixing the dye with a water soluble silver salt.
• the resulting complex can be used in the reaction solution or colloidal suspension without being isolated.
• an equi-molar quantity of silver to dye is necessary to form the complex.
• Dyes used in preparing the light-sensitive silver dye complexes are advantageously water soluble, but in the event that they are substantially insoluble in water, solutions can be obtained by dissolving them in sufficient water miscible solvent.
• the water miscible solvent is not critical but may be chosen from those which are compatible with any colloid which is used as a binder or coating medium.
• the reaction to form the complex can be carried out in a suitable solvent.
• such salts can, as noted above regarding silver-dye complexes, be dispersed first in a hydrophilic colloid material such as gelatin after which this existing dispersion is itself dispersed and coated according to the subject invention as long as each dispersed member, including the hydrophilic colloid, is substantially insoluble in the dispersion medium.
• a mixed grain color photographic element such as those described in US. Pats. 2,388,859 and 2,614,925,
• crystals of a radiation-sensitive silver salt or mixtures thereof are dispersed in a dielectric fluid medium by stirring or otherwise agitating the silver salt particles to prevent settling and maintain the particulate dispersion.
• a convenient agitation means for liquid media is provided by ultrasonic vibration apparatus, whereas spraying or fluidized bed techniques are advantageous Where the dispersion medium is a gaseous fluid.
• Liquid dispersion media are suitably non-aqueous. Due to the difficulty of obtaining advantageous electrical insulating properties with aqueous media, highly insulating organic liquids are preferred. Additionally, Where the silver salt is predispersed in a hydrophilic colloid, the liquid dispersion medium is preferably one in which all dispersed components are insoluble.
• Such advantageous organic dlS- persion media include, for example, hydrocarbon species typically having 4-12 carbon atoms including aliphatic hydrocarbons such as isobutane, n-hexane, n-heptane, as well as other branched and straight chain hydrocarbons and cyclic hydrocarbons such as cyclohexane, etc.
• Additional advantageous liquid dispersion media include halogenated hydrocarbons such as carbon tetrachloride, chlorinated fiuorinated lower alkanes, isoparaffinic hydrocarbons such as Isopar G (Humble Oil and Refining Co.), and the like.
• halogenated hydrocarbons such as carbon tetrachloride, chlorinated fiuorinated lower alkanes, isoparaffinic hydrocarbons such as Isopar G (Humble Oil and Refining Co.), and the like.
• Gaseous dispersion media are widely variable and include a wide selection of materials such as air or any of the conventional aerosol propellant gases, such as nitrogen, which are substantially non-reactive with the photosensitive species or colloids described herein.
• Electrostatic deposition of the subject silver salts onto a charged support from a liquid medium is promoted by the double layer charge relationship at the contact interface between the liquid medium and the dispersed solid.
• the ionic distribution can be such that a varying excess of either positive or negative ions exist at the solid surface.
• Such ionic distribution is related to the choice of dispersion medium. Accordingly, the relationship of the dispersed phase and the medium can affect the polarity and the magnitude of the double-layer charge. The polarity of the double layer determines whether a particle will behave like a positively or negatively charged entity under the influence of an electric field.
• a surfactant or surface active agent can be employed in conjunction with the dispersion to either impart or modify the double-layer charge that exists at the solidliquid interface.
• Typical surfactants include such compounds as metal salts of long chain fatty acid and cyclic organic carboxylic acids, e.g. cobalt naphthenates, aluminum stearate, etc.; long chain quaternary ammonium salts, e.g. lauryl trimethyl ammonium chloride and metal salts of long chain alkylsulfonic acids, e.g. sodium lauryl sulfonate.
• a charge of the desired polarity can be imparted to the dispersed particles by directing them past a charged point or grid.
• a charged source typically a rod or pin
• the dispersed particles receive a charge of like polarity as they pass by the charged source.
• a radiationsensitive silver salt is electrostatically deposited upon an electrically insulating member which functions as the support for the resultant photographic element.
• electrically insulating members which can also be termed electrical insulators or dielectric members or supports, are advantageously formed from materials having a surface resistivity in excess of about ohms per square as measured by Van der Pauw technique, described in Phillips Research Report, 13, 1-9 (1958).
• Exemplary of electrically insulating support members are supports fabricated from electrically insulating resins such as cellulose triacetate, cellulose acetate butyrate, polystyrene, poly- (vinylbutyral), poly(ethylene terephthalate), polyethylene, polypropylene, etc.
• the subject supports are advantageously laminates, having at least one electrically insualting surface.
• a thin layer of an electrically insulating material such as the described polymeric resin compositions, can be laminated to a second material, such as paper, to provide a composite support which possesses the requisite electrically insulating surface.
• a support member such as paper, metals, wood, etc., can be overcoated with an electrically insulating layer to provide an advantageous composite support material.
• Widely varied alternative supports can be used, With the only requirement being the existence of at least one electrically insulating surface.
• an electrically insulating support such as those described elsewhere herein is first electrostatically charged such as by friction, by exposure to a corona discharge source or another like means that is effective to impart an electrostatic charge to the electrically insulating support surface.
• the surface is raised to a potential of at least about 50 volts.
• Conveniently used voltages conventionally range up to about 1,500 volts, but voltages in excess of 1,500 can be used for particular situations if desired.
• the support member, bearing an electrostatic charge on a surface thereof, is then immersed, either partially or totally, into a silver salt dispersion of this invention.
• the support can be advantageously charged to the opposite negative or positive polarity. Since the surface charges present on the support and the dispersed silver salt grains are of opposite polarity, the silver salt particles are attracted to and deposited upon the support whereupon they from a composite, substantially binderless coating of silver halide crystals or grains.
• the silver salt crystals can be predispersed in a hydrophilic colloid such as gelatin or polyvinyl alcohol, and this resultant dispersion can then be dispersed in a liquid medium as described elsewhere herein. After the desired deposition has been obtained ,the coated support is removed from the dispersion and dried, thereby preparing a composite photographic element.
• the support charged as described above, is exposed to an aerosol of dispersed particles which have been oppositely charged by techniques such as those previously described.
• Convenient aerosol formers include fluidized bed apparatus, spray apparatus, etc.
• the charged dispersed particles are drawn to the oppositely charged support where they adhere to form a composite, radiationsensitive photographic element.
• the resultant sensitive, silver salt layer can be substantially binder free or can contain a hydrophilic binder if the silver salt crystals (e.g. silver-dye complex) are predispersed in a hydrophilic colloid prior to the coating operation.
• the dispersed silver salt can comprise either one silver salt or mixtures thereof sensitized, for example, to record light of various portions of the spectrum as is required for the preparation of full color photographic images.
• the uniformity of the deposit, whether it be from a liquid or gaseous medium, can be advantageously improved particularly in the case of thin coatings by having an electrode, known as a Development Electrode, separated from but in close proximity to the charged surface of the support.
• the electrostatic coating process of this invention provides a number of advantages over presently employed flow or extrusion-type coating techniques for the preparation of light-sensitive, photographic layers.
• the amount of material deposited is primarily a function of the electrostatic charge per unit area and by the charge on the particles of the dispersed phase. As such, it is a demand situation and does not require intricate supply mechanisms such as variable pumps. Additionally, the amount of dispersion medium deposited is very small relative to the deposited radiation-sensitive silver-salt crystals, and it is not necessary to provide evaporative or other elaborate removal means for the deposited dispersion medium. Additionally, flat, curved or irregularly shaped supports can be coated with substantial uniformity by electrostatic coating means.
• a completely prepared photographic element is removed from contact with the dispersion and dried, it can be imagewise exposed, developed and fixed or otherwise stabilized to yield a permanent photographic silver image.
• Exposure is to a suitable radiation source, e.g. X-rays, visible light, ultra-violet light, etc., whereupon a metallic silver latent image is produced in the electrostatically deposited silver salt layer.
• Developing the latent image to a visible photographic silver image is accomplished in the case of monochromatic elements by treating the image- Wise exposed photographic element with a photographic developing composition.
• Such developing compositions incorporate a silver halide developing agent, typically polyhydroxy benzenes like hydroquinones, catechols and pyrogallols, as well as other polyhydroxy compounds such as ascorbic acid.
• Additional developing agents include aminophenols, p-phenylenediamines and 3-pyrazolidones.
• silver halide developing agents that are advantageously used herein are compounds like 2- methyl-3-chlorohydroquinone, bromohydroquinone, catechol, S-phenylcatechol, pyrogallol monomethylether(lmethoxy 2,3 dihydroxy benzene), S-methylpyrogallol monomethylether isoascorbic acid, N-methyl-p-aminophenol, dimethyl-p-phenylene diamine.
• the photographic silver image is stabilized by treatment with a photographic fixing bath including a fixing agent to remove undeveloped silver salt.
• a photographic fixing bath including a fixing agent to remove undeveloped silver salt.
• Conventional fixing agents or silver halide solubilizing agents include water-soluble thiosulfates, thiocyanates and mercaptans such as ammonium thiosulfate, sodium thiocyanate and the disodium salt of 2-mercapto-4-hydroxy-S-aminopyrimidine.
• a particularly preferred fixing agent is sodium thiosulfate.
• Stabilization is generally accomplished by treatment with a fixing bath that incorporates a fixing agent such as those mentioned previously. Exemplary of fixing baths is one having the formula:
• a mixed grain dispersion suitable for deposition according to the present invention to prepare a full color photographic element can be made by codepositing silver halide grains that are spectrally sensitized to record particular light ranges.
• silver chlorobromide grains that are sensitized to record red light by a photographic spectral sensitizing dye can be dispersed in a suitable medium, such as those described herein, along with silver bromide grains that are sensitized to record green light by a photographic spectral sensitizing dye.
• a hydrophilic colloid material is utilized as a medium in which each of the types of silver halide grains is predispersed.
• the codispersed silver halide grains can then be electrostatically deposited on an electrically insulating stipport according to the above-described procedures of the subject invention.
• Unsensitized silver halide grains treated with a yellow filter dye can then be electrostatically deposited in a second blue sensitive layer over and contiguous to the first described layer containing silver halide sensitized to record light of the red and green portions of the spectrum.
• Such a composite element upon imagewise exposure and processing, produces full color photographic images.
• a mixed grain emulsion of the type described in US. Pat. 2,388,859 can be prepared according to the electrostatic coating process of the subject invention.
• One photosensitive layer is electrostatically deposited, such a layer including fast silver halide grains sensitized to record the blue spectral region and slow silver halide grains sensitized to record the red and green spectral regions.
• the sensitivity of the grains primarily sensitive to blue light is considerably greater than the blue light sensitivity of either the red or the green sensitized silver halide grains.
• a yellow colored filter layer which absorbs enough blue light so that the speed of the fast blue sensitive component of the mixed grain emulsion is reduced to a value equivalent to those of the red and green speeds of the two other components.
• a yellow filter absorbing 98% of the overall blue light may be used.
• Such a filter can be one containing a dye of the pyrazolone type exemplified by tartrazine.
• This filter would reduce the blue speed of the red and green sensitive components of the mixed grain emulsion to approximately 2% of the speeds of the red and green thereby rendering the blue sensitivity of these grains negligible for printing purposes.
• the high speed blue sensitive emulsion still prints the blue record at the same speed required for printing the red and green records onto the other two components.
• This yellow filter layer can be, for example, flow coated from an aqueous gelatin solution subsequent to electrostatically depositing the photosensitive silver halide grains.
• a mixed grain element prepared as described herein can be imagewise exposed and developed in a conventional silver halide developing composition to produce a negative silver image.
• a conventional silver halide developing composition to produce a negative silver image.
• Exemplary of such a developer is one having the formula:
• the element after negative development has a negative silver image produced by the blue exposure, a negative silver image produced by the green exposure and a negative silver image produced by the red exposure. In each layer, there remain unexposed and undeveloped grains having the three recited light sensitivities.
• the film can then be light-exposed through the base through a red filter transmitting light of longer wavelength than about 640 millimicrons, to expose the residual red sensitive grains and can then be developed in a color-forming developer which can have the following composition:
• the film can then be exposed from the support side to green light to expose the residual green sensitive grains and the film can then be developed in a developer which may have the following composition:
• the film can then be exposed to white light to expose the residual blue sensitive silver halide grains and developed in a developer which may have the following composition:
• the film is washed and bleached in a solution having a formulation such as the following composition:
• the radiation-sensitive layer has, as the sensitive component, silver-dye complex crystals or mixtures thereof
• imagewise exposure to a suitable source of radiation is followed by physical development to prepare a photographic image. Exposure of the sensitive silver-dye complex produces physical development nuclei in exposed areas.
• Typical reducing agents used in the physical developer include, for example, polyhydroxy-substituted aryl compounds such as hydroquinones, catechols and pyrogallols; ascorbic acid derivatives; aminophenols; p-phenylenediamines, and the like developing agents used in the photographic art.
• cm. pieces of polyethylene-coated paper serve as the support material.
• Five 17 x 20 mm. areas on each support strip are electrostatically charged by exposure to a corona through a screen grid in such a way as to charge each of the areas to a diflerent potential from to 1000 volts. All charged areas on any one strip have the same polarity which can be either positive or negative.
• a positively charged support strip is bathed for 30 seconds in the silver bromide-hexane dispersion, removed, and allowed to dry, thereby preparing a photographic element having a substantially binderless layer of crystalline silver bromide. Visual examination indicates that silver bromide is deposited predominantly in the charged areas.
• the treated support strip is then exposed for one second through a neutral density step tablet to the ambient room light provided by watt tungsten lamps positioned at a distance of about five feet from the exposure plane.
• the exposed element is then developed for 15 seconds in a photographic developer solution having the formula:
• the resultant photographic element is then exposed to a tungsten light source on a .3 log E wedge spectrograph, developed 30 seconds in a photographic developer solution, fixed, washed and dried, all processing as in Example 1.
• a photographic silver image of the spectrograph is produced in the photographic layer.
• EXAMPLE 4 A gelatino, silver bromoiodide emulsion as described in Example 3 but also including the spectral sensitizing dye 3,3-diethyl-9-methylthiacarbocyanine bromide in an amount of 100 mg. per mole of silver based on the silver halide. After coating, exposure and development as in Example 3, the photographic element exhibits an image of the spectrograph with increased sensitization being achieved over a broad band of from 400 to 600 nm.
• EXAMPLE 5 Electrostatic deposition from an aerosol dispersion: grams of a fine grain gelatin bromoiodide emulsion containing 1 mole silver, 25 grams gelatin and 25 grams of copoly 3-thiapentylacrylate-3-acryloxypropanel-sulfonic acid, sodium salt per 1.09 kilograms is added to 300 ml. of a pure grade cyclohexane containing 0.30 gram sorbitan monooleate, and the mixture is blended with stirring for 8 minutes.
• Example 1 A photographic silver image appears where the element is exposed, and it is evident that the silver halide is deposited on the negatively charged area.
• EXAMPLE 6 Two dispersions of silver bromoiodide emulsions are prepared as in Example 3 except that each portion of silver bromoiodide is treated with a different spectral sensitizing dye, the first being sensitized to record red light with 8- phenyl-3,4,3',4-dibenzothiacarbocyanine bromide and the second being sensitized to record green light with 3,4- beuzothia-2-cyanine bromide.
• the solids are separated, washed and codispersed in equal quantities (5 g. each) in cyclohexane containing sorbitan monooleate as in Example 3 and according to the stirring and ultrasonic dispersing technique of Example 3.
• Electrostatic coating of this mixed grain dispersion is accomplished as in Example 3. After drying, portions of the composite photographic element are first exposed on a wedge spectrograph through red and green filters respectively and then developed and fixed according to the procedure of Example 1. The resultant negative silver images indicate the desirable red and green light sensitivity present in the coated layer.
• An electrostatic coating process for preparing a photographic element comprising a support having an electrically insulating surface of a surface resistivity in excess of about 10 ohms per square on which is coated a radiation-sensitive layer comprising preformed silver salt crystals, said process comprising:
• silver salt is a silver halide salt selected from the group consisting of silver bromide, silver chloride, silver iodide and co-crystals and mixtures thereof.
• An electrostatic coating process for preparing a photographic element comprising a support having an electrically insulating surface of a surface resistivity in excess of about 10 ohms per square on which is coated a radiation-sensitive layer comprising preformed silver salt crystals, said process comprising:
• silver salt crystals are silver halide crystals selected from the group consisting of silver bromide, silver chloride, silver iodide and cocrystals and mixtures thereof.

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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)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (1)

Publications (1)

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Cited By (2)

• 1970
  • 1970-03-19 US US21174A patent/US3690918A/en not_active Expired - Lifetime
• 1971
  • 1971-02-10 CA CA104,978A patent/CA965288A/en not_active Expired
  • 1971-03-16 FR FR7109098A patent/FR2084673A5/fr not_active Expired
  • 1971-03-16 BE BE764354A patent/BE764354A/fr unknown
  • 1971-04-19 GB GB2455871*A patent/GB1336671A/en not_active Expired

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