Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/09—Sensitisors or activators, e.g. dyestuffs

Definitions

• Photosensitive silver halide is spectrally sensitized by forming a dispersion of a substantially water-insoluble spectral sensitizing dye in a hydrophilic colloid, and incorporating the dispersion of dye in colloid in a light sensitive system comprising photosensitive silver halide dispersed in a hydrophilic colloid.
• This invention relates to new processes for spectrally sensitizing photographic materials, and to new compositions useful in such processes.
• photosensitive materials dispersed in a hydrophilic colloid which are sensitized in accordance with this invention tend to exhibit lower fog and generally higher sensitized speed than similar emulsions spectrally sensitized in accordance with prior art procedures.
• sensitized photographic materials may be coated at high speeds without the occurrence of coating defects caused by organic solvents in the system. Organic solvents were previously necessary in fairly large quantities in order to introduce the sensitizing dye in the emulsion.
• spectral sensitizing dyes for photosensitive materials are highly insoluble in water.
• aqueous systems such as a dispersion of a photosensitive material, e.g., silver halide, in a hydrophilic binder such as gelatin.
• Most of these dyes are so insoluble that large quantities of organic solvent are required to dissolve the dye for incorporation into the aqueous system.
• hydrophilic colloid systems serious problems are encountered, such as coating defects when coating the hydrophilic colloid system on a support. It would, therefore, be highly desirable if an improved process could be provided for incorporating water-insoluble dyes in hydrophilic systems.
• This invention solves the problem of excess solvent when incorporating water-insoluble dyes in hydrophilic colloids containing photosensitive materials, and in addition normally provides an unexpected reduction in fog and, generally, an increase in sensitized photographic speed. Since only extremely small quanties of organic solvent are employed in the process of the invention, difficulties such as coating problems arising from prior art techniques are avoided.
• One object of this invention is to provide a novel process for spectrally sensitizing photosensitive materials.
• a further object of this invention is to provide a novel process for dispersing sensitizing dyes in hydrophilic colloids containing photosensitive materials, such as silver halide.
• Still another object of this invention is to provide a process for making dispersions of sensitizing dye in hydrophilic colloids.
• Another object of this invention is to provide novel dispersions of dye in hydrophilic colloids.
• photosensitive materials are spectrally sensitized by forming a dispersion of a spectral sensitizing dye in a hydrophilic colloid, and the photosensitive material is then contacted with said dispersion.
• a spectral sensitizing dye is incorporated in a hydrophilic colloid by dissolving the dye in an organic solvent, and then adding the dissolved dye to a hydrophilic colloid.
• compositions comprising dispersions of spectral sensitizing dye in a hydrophilic colloid which is essentially free from photosensitive materials, the particles of the dye in the colloid having an average diameter of less than about 1.0 micron.
• the solvent is heated to dissolve the dye in as high a concentration as possible.
• the solution of dye is then combined with a hydrophilic colloid, such as an aqueous gelatin solution.
• a wetting agent may advantageously be employed to aid in dispersing the dye in the hydrophilic colloid.
• the dispersion of dye in hydrophilic colloid may be milled or homogenized.
• the solvent employed to dissolve the dyes is a substantially water-immiscible organic solvent which has a sufficiently high vapor pressure to volatilize from the dispersion upon drying. After forming the dispersion of dye in hydrophilic colloid, the dispersion is dried to remove essentially all of the solvent.
• EXAMPLE 1 A negative speed gelatino-silver bromoiodide emulsion is digested to optimum sensitivity with a mixture of labile sulfur compound and a soluble gold salt, and divided into two portions. These portions are spectrally sensitized in the 5000 to 6000 A. range as follows:
• Dye I a benzothiazolylidene-isopropylideneoxazolidinedione merocyanine dye of the type described in Example 7 of US. Patent 2,165,338, is added to the melted emulsion with good agitation at the rate of 0.132 g. per mole of silver halide from an acetone solution.
• the Wetting agent used in this example is an alkylnaphthalene sodium sulfonate product sold as Alkanol B by Du Pont.
• Each emulsion is further treated by the addition of a magenta-forming coupler of the pyrazolone type suitably dispersed in a high boiling solvent.
• the emulsions are then coated on a suitable support.
• the resulting coatings are exposed for /2 second to the light emitted by a 500- watt tungsten lamp adjusted to 2650" K. in an intensity scale sensitometer further modified by a Wratten No. 15 filter and processed by the color negative process disclosed by Hanson, Jr., and Kisner in Journal of the Society of Motion Picture and Television Engineers,
• EXAMPLE 2 A negative speed gelatino-silver bromoiodide emulsion digested to optimum sensitivity with a mixture of liable sulfur compound and a soluble gold salt is divided into two portions. These portions are optically sensitized in the 5000 to 6000 A. region as follows:
• Dye I g 0.130 Benzene cc Ethyl acetate cc 65 10% aqueous gelatin cc 200 5% aqueous alkanol B cc 75 The dispersion is formed as in Example 1(b), dried and added to the emulsion as the plumped and melted dispersion at the rate of 0.132 g. of dye per mole of silver halide.
• Each emulsion is further treated by the addition of a magenta forming coupler of the pyrazolone type suitably dispersed in a high boiling solvent.
• the emulsions are then coated on a suitable support.
• the resulting coatings are exposed for second to the light emitted by a 500-watt tungsten lamp adjusted to 2650 K. in an intensity scale sensitometer further modified by a Wratten No. filter and processed as in Example 1. The following results are obtained:
• EXAMPLE 4 Antifoggant action of dispersion sensitization is also evident in reversal processing of emulsions in the process described in U.S. Patent 2,294,898, col. 11, as Color Process 1. Slightly larger amounts of dye are used to increase the speed of the reference coating. Substantial antifoggant action is evident at these higher concentrations of dye and is found in the black and white developing step as lower D and in full reversal color process as higher D The following results are obtained on coatings prepared as in Example 2 above with the exception of the higher concentration of dye as indicated.
• Example 5 shows a preferred method of dispersing spectral sensitizing dyes in hydrophilic colloids.
• the dye is first dissolved in a highboiling, partially water-miscible solvent.
• the dye is dissolved in heated solvent to provide as high a concentration of dye in the solvent as possible.
• the concentrated solution of dye is then dispersed in an aqueous hydrophilic colloid, and the mixture is preferably milled or homogenized.
• This procedure results in an oil-in-water emulsion featuring small particle size globules of solvent containing the dye.
• This dispersion of dye in hydrophilic colloid may be used to sensitize photosensitive materials. If desired, the dispersion can be set and stored until it is desired to use the dispersion to sensitize a photographic material.
• dye A is normally dissolved in methanol at 0.05 g. per 11. oz. of methanol, and dye B at 0.025 g. per 11. oz. of methanol.
• the phenoxyethanol was heated to 220 F. for dye A and 180 F. for dye B in the above samples.
• prior art methods resulted in the introduction of 1952 ml. of organic solvent into an emulsion, whereas to introduce the same concentration of dyes, only 120 ml. of organic solvent are introduced into the system.
• the high boiling solvent solution of dye is, while hot, mixed into an aqueous solution of gelatin containing a surfactant, and milled or homogenized.
• the resulting dispersion is allowed to set and may be stored, e.g., at about 40 to 50 F.
• the set gel is added directly to a warm silver halide emulsion, where it is dissolved causing the sensitizing dye to precipitate as a crystalline or amorphous solid dispersion of very fine, uniform particle size (average diameter is under 1 micron).
• the very fine dye dispersion obtained has a high surface area to mass ratio which promotes dye dissolving and transfer to the silver halide grains. Similar results are obtained when the phenoxyethanol is replaced with n-butanol, and with ethyl acetate.
• Example 6 The lower fog and higher sensitized speed of emulsions sensitized with the dispersion of Example 5 are shown in Examples 6 and 7.
• EXAMPLE 6 Two multilayer color films are prepared as described in Example 1 of Van Campen U.S. Patent 2,956,879.
• the green sensitive emulsion is spectrally sensitized with an oxazole-thiohydantoin dye of the type described in Example 3 of Brooker US. Patent 2,282,116 using about 180 mg. per mole of silver halide.
• the dye is added from a solution consisting of mg. of dye per ml. of acetone-methyl alcohol 1:1.
• the dye is in the form of a dispersion in gelatin containing 2 g. of dye per pound of dispersion prepared as described in Example 5 (the set dispersion of dye in gelatin is added to the warmed emulsion).
• coated films are exposed and developed for 25 minutes in a developer of the type described in Example 1 of US. Patent 2,956,879 and processed as described in this patent with the following results.
• the following example illustrates the increase in sensitivity that can be obtained using sensitizing dye dispersions.
• EXAMPLE 7 Two multilayer coatings containing dye-developers are prepared as described in Example 1 of Weyerts and Salminen US. Patent 3,146,102.
• the red sensitive emulsion is spectrally sensitized with a thiacarbocyanine dye of the type described in Example 9 of Sprague US. Patent 2,503,776 using about 140 mg. of the dye per mole of silver halide.
• the dye is added from a solution consisting of 120 mg. of dye per 30 cc. of methyl alcohol.
• the dye is added in the form of a dispersion containing 2 g. of dye per pound of dispersion prepared as described in Example 5 (the set dispersion of dye in gelatin being added to the warm emulsion).
• the coated films are exposed and processed as described in U.S. Patent 3,146,102 using an activator similar to activator IV Q described in this patent. The following results were obtained.
• Dye dispersion 151 Results similar to those in Examples 6 and 7 are obtained when the solvent is n-butanol and instead of gelatin, the hydrophilic colloid is polyvinyl alcohol.
• sensitizing dye dispersions and sensitizing photosensitive materials is further illustrated in the following example.
• This example shows the technique of dissolving a spectral sensitizing dye in a volatile, watermiscible solvent, and adding this solution to a heated aqueous solution of hydrophilic colloid, which is then chilled and set. The solvent vaporizes from the colloid, leaving a fine dispersion of dye crystals in the colloid. This dispersion may then be used to spectrally sensitize photosensitive materials. No milling or homogenizing of the dispersion is necessary in this method to get very fine crystals of dye.
• EXAMPLE 8 A cyanine dye (a 2,2-cyanine) 1.6 grams) is refluxed in 4.2 fl. oz. of methanol, and when it is dissolved the hot solution is immediately poured into 18 fl. oz. of well agitated 5% aqueous gelatin solution at F. The resulting dispersion is immediately cooled and set. This dispersion is then added to a gelatin silver halide emulsion to spectrally sensitize the silver halide, with results similar to those of the above examples.
• This invention is applicable to spectral sensitizing dyes which are substantially insoluble in aqueous solutions.
• Spectral sensitizing dyes with which this invention are concerned generally have a solubility in water (at 20 C.) of less than about 1%.
• useful spectral sensitizing dyes are the eyanine dyes, the hemicyanine or merocyanine dyes, styryl dyes and the like, such as:
• Oxonal dyes such as 3-hydroxy3-oxy-2.2-methenyldithionaphthene; phthaleins such as erythrosine;
• Photosensitive materials which can be spectrally sensitized include silver halide, such as silver bromide, silver chloride, silver iodide, and mixed silver halides such as silver chloroiodide and silver bromoiodide.
• Other photosensitive materials may be spectrally sensitized by this invention, such as TiO or ZnO.
• the photosensitive material to be sensitized may be dispersed or suspended in a hydrophilic colloid binder solution, or the dispersions of this invention may be applied over binder-free deposits of the photosensitive material, such as supports having vacuum deposited thereon a light sensitive silver halide layer.
• any suitable solvents may be used for dissolving the dyes, the cyanines generally being soluble in lower alco hols such as methanol and the merocyanines generally having good solubility in ketones such as acetone.
• the organic solvents which may be used may be water-miscible, water-immiscible or partially water-miscible.
• the solvent used has a sufliciently high vapor pressure to volatilize from the hydrophilic colloid, thereby providing compositions which may be entirely free of organic solvent, or compositions which contain such a small quantity of organic solvent that coating problems are avoided.
• partially water-miscible solvents such as organic solvents having a solubility between 1 and 8 percent at room temperature (20 C. or 68 F.) and a boiling point above 175 F.
• Typical preferred solvents of this type are:
• the particle size of the dye crystals in the hydrophilic colloid have an average diameter of less than about 1 micron. Dispersions of dyes having large particle size do not effectively sensitize photographic materials.
• the process of spectrally sensitizing hydrophilic photosensitive systems in accordance with this invention is particularly useful when the system is being coated at high speeds, such as over 150 feet per minute.
• the dispersions of sensitizing dye provided by this invention may be incorporated in warm solutions of the hydrophilic photosensitive system shortly before coating.
• the photosensitive system in which the dispersions are being incorporated may be concentrated; for example, gelatin silver halide emulsions in which more than such as /3 or more, of the gelatin emulsion is silver halide, and the emulsion viscosity is at least 50 cps, such as 500 cps. or more.
• the small amount of organic solvent employed in the processes and dispersions in accordance with this invention allows high speed coating with such concentrated emulsions since only small quantities of organic solvent are present.
• Large quantities of organic solvents cause coating defects in various ways, such as by causing local dehydration of the hydrophilic colloid which results in particulate matter which cannot readily be redispersed. This particulate matter remains in the composition causing coating defects such as streaks or spots.
• the process of sensitizing as described herein is highly useful in wet-on-wet coatings, and high speed coatings such as the coating techniques described in British Patents 855,- 216; 925,179; US. Patents 2,620,285 and 2,681,294.
• the coating may be applied simultaneously with at least one other layer such as by using the procedures described in U.S. Patents 2,941,898 of N. R. Wynn or in 2,761,791 of T. A. Russell.
• the coating operation is conveniently carried out using an emulsion having a viscosity of 50- centipoises and a coating speed of 150500 feet per minute.
• the dispersions of sensitizing dye and hydrophilic colloid provided herein are highly stable.
• prior art solutions of spectral sensitizing dye in organic solvent remain stable for a very short time.
• This feature of the novel dispersions of the dye is highly useful in commercial operations, since dispersions of the dye can be formed and stored for relatively long periods of time until required in the course of manufacturing sensitized materials.
• hydrophilic, water-permeable organic colloids can be suitably utilized in preparing the dispersions of sensitizing dyes of this invention.
• Gelatin is preferably utilized although other colloidal material such as colloidal albumin, cellulose derivatives, synthetic resins or the like can be utilized.
• Suitable colloids that can be used are polyvinyl alcohol or a hydroyzed polyvinyl acetate as described in Lowe, US. Patent 2,286,215, issued June 16, 1942; a far hydrolyzed cellulose ester such as cellulose acetate hydrolyzed to an acetyl content of 19 to 26% as described in US. Patent 2,327,808 of Lowe and Clark, issued Aug.
• a still further advantage of the processes and compositions of this invention is the reduction in hazard in employing smaller quantities of organic solvents and less flammable solvents, thereby reducing hazards of fire, explosion or toxicity.
• sensitizing dye in hydrophilic colloid could be used to spectrally sensitize photosensitive materials dispersed in a hydrophilic colloid. It would not be expected that the sensitizing dye would diifuse through an aqueous solution of hydrophilic colloid in which the dye is relatively insoluble and become adsorbed to a photosensitive material such as silver halide crystals.
• a light sensitive system comprising silver halide dispersed in a hydrophilic colloid to spectrally sensitize the silver halide photosensitive material.
• a hydrophilic colloid selected from the group consisting of gelatin; polyvinyl alcohol; cellulose acetate hydrolyzed to an acetyl content of from 19 to 26%; water-soluble ethanolamine cellulose acetate; polyacrylamide having a combined acrylamide content of 30 to 60% and a viscosity of 0.25 to 1.5; an imidized polyacrylamide having a combined acrylamide content of 30 to 60% and a viscosity of 0.25 to 1.5; zein; and, the polymeric material which results from polymerizing a protein with a monomer having a vinyl group, said hydrophilic colloid being essentially free from silver halide; and,

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Colloid Chemistry (AREA)

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Citations (6)

• 1965
  • 1965-06-21 US US465736A patent/US3469987A/en not_active Expired - Lifetime
• 1966
  • 1966-06-10 BE BE682413D patent/BE682413A/xx unknown
  • 1966-06-16 DE DE19661547705 patent/DE1547705A1/de not_active Withdrawn
  • 1966-06-21 GB GB27678/66A patent/GB1154781A/en not_active Expired

Patent Citations (6)

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