US3632348A - Methine dye sensitizers for emulsions exposed at{31 180{20 {0 c. - Google Patents

Methine dye sensitizers for emulsions exposed at{31 180{20 {0 c. Download PDF

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US3632348A
US3632348A US822670A US3632348DA US3632348A US 3632348 A US3632348 A US 3632348A US 822670 A US822670 A US 822670A US 3632348D A US3632348D A US 3632348DA US 3632348 A US3632348 A US 3632348A
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silver halide
exposed
dye
emulsion
silver
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Thomas H James
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Eastman Kodak Co
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Eastman Kodak Co
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    • 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
    • G03C1/005—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein
    • G03C1/06—Silver halide emulsions; Preparation thereof; Physical treatment thereof; Incorporation of additives therein with non-macromolecular additives
    • G03C1/08—Sensitivity-increasing substances
    • G03C1/10—Organic substances
    • G03C1/12—Methine and polymethine dyes

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  • the highest occupied electronic energy level of the methine dye adsorbed on the silver halide is more positive than the highest occupied energy level in the valence band of the silver halide, and the lowest vacant electronic energy level of the dye adsorbed on the silver halide is more positive than the conduction band of the silver halide.
  • Particularly good results are obtained with the quinoline monomethine cyanines.
  • Preferred results are obtained when the dye is employed in a concentration sufiicient to give monomolecular layer coverage of the silver halide grains.
  • This invention relates to photographic processes, and more particularly to photographic processes in which silver halide emulsions are exposed at low temperatures.
  • One object of this invention is to provide a photographic process in which a silver halide emulsion is exposed at low temperatures.
  • Another object of this invention is to provide a photographic process which results in improved sensitivity of photo graphic silver halide emulsions when exposed at low temperatures.
  • Still another object of this invention is to provide photographic processes which result in images of increased contrast when silver halide emulsions are exposed at low temperatures.
  • an improvement is provided in the process for making photographic images by exposing a light-sensitive photographic silver halide emulsion to radiation at temperatures below about 1 80 C. to produce a latent image, and then developing the latent image to a silver image.
  • the improvement in accordance with this invention which comprises employing in the process a negative, unfogged, photographic silver halide emulsion having a methine dye adsorbed thereto, the highest occupied electronic energy level of the dye adsorbed on the silver halide being more positive than the highest occupied energy level in the valence band of the silver halide, and the lowest vacant electronic energy level of the dye adsorbed on the silver halide being more positive than the conduction band of the silver halide.
  • the quantity of dye used is sufficient to increase the sensitivity and the contrast of the emulsion when it is exposed at low temperatures.
  • concentration of the dyes employed in the practice of the invention is generally much higher than amounts of dye used to sensitize photographic silver halide emulsions for normal temperature exposures.
  • the practice of the present invention results in substantial increases in speed on lowtemperature exposure.
  • very high contrast can be obtained in the practice of the present invention; the contrast can be similar to that obtained with lith-type emulsions used with lith-type developers.
  • methine dyes generally decrease low-temperature sensitivity, as shown by West, Photographic Science and Engineering, Volume 6, No. 2, page 92 1962) at page 100.
  • FIG. 1 curve 4 of FIG. 1
  • FIG. 2 curves 7 and 8
  • FIG. 3 curve 13
  • any methine dye can be used in the practice of the invention, provided the highest occupied electronic energy level of the dye adsorbed on the silver halide is more positive than the highest occupied energy level in the valence band of the silver halide, and the lowest vacant electronic energy level of the dye adsorbed on the silver halide is more positive than the conduction band of the silver halide.
  • the highest occupied electronic energy level of methine dyes adsorbed on silver halide is preferably more negative than the conduction band of the silver halide.
  • the highest occupied electronic energy level of a methine dye adsorbed on silver halide, and the lowest va cant electronic energy level of a methine dye adsorbed on silver halide can be calculated by the method described by Tani and Kikuchi, Photographic Science and Engineering, Volume 11, No. 3, page 129 (1967) and Tani, Kikuchi, and Honda in Photographic Science and Engineering, Vol. 12, No. 2, page 1968).
  • the highest occupied energy level in the valence band of silver halide and the bottom conduction band of the silver halide has been determined by those skilled in the art. See, for example, Mees, and James, The Theory of the Photographic Process, Third Edition, (the MacMillan Company, 1966), pages 19-21, 264 and 265, and Tani, Kikuchi, and Honda, Photographic Science and Engineering, Volume 12, No. 2, (1968) page 80.
  • the highest occupied energy level of the valence band of silver halide is about 6.0 ev. relative to 0 for vacuum, and the bottom of the conduction band of silver halide is about 3.5 ev.
  • any of the methine dyes including the styryl and cyanine methine dyes, can be employed in the practice of the invention, provided the dyes when adsorbed to silver halide, including adsorption in their aggregated state, have a highest occupied electronic energy level and a lowest vacant electronic energy level, respectively, that is more positive than the highest occupied energy level in the valence band of the silver halide and the bottom conduction band of the silver halide.
  • methine dyes which meet the above criteria and have at least one of the following formulas:
  • h, m, n and p each represents an integer of from 1 to 2;
  • R R and R each represents an alkyl group, including substituted alkyl, (preferably a lower alkyl containing from one to four carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, etc., and substituted alkyl groups (preferably a substituted lower alkyl containing from one to four carbon atoms), such as a hydroxyalkyl group, e.g., ,B-hydroxyethyl, whydroxybutyl, etc., an alkoxyalkyl group, e.g., B-methoxyethyl, w-butoxybutyl, etc.,
  • an oxazole nucleus e.g., 4-methyloxazole, S-methyloxazole, 4-phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5-dimethyloxazole, S-phenyloxazole, benzoxazole, 5-chlorobenzoxazole, S-methylbenzoxazole, 5- phenylbenzoxazole, 6-methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, S-methoxybenzoxazole, S-ethoxybenzoxazole, S-chlorobenzoxazole, o-methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroxybenzoxazole, naph
  • Dyes of formula 1 above wherein h represents 1 and Z, and Z, each represents a quinoline nucleus, i.e., quinoline monomethine cyanine dyes, provide particularly good results in the practice of this invention.
  • Some specific dyes which can be used in this invention are listed below:
  • the invention can be practiced with any of the light-sensitive photographic silver halides, including silver bromide, silver bromoiodide, silver chloride, silver chlorobromide, and silver chlorobromoiodide.
  • Silver bromoiodide emulsions in which the halide is at least mole percent bromide are especially useful in the practice of the invention.
  • the silver halide grains can be of any suitable type, such as octahedral or cubic grain. Conventional negative, developing-out, unfogged silver halide emulsions are used in this invention.
  • the silver halide emulsion may contain chemical sensitizers, antifoggants, stabilizers, speed-increasing compounds, hardeners, plasticizers, and may utilize the binders described and referred to in Beavers U.S. Pat. No. 3,039,873 (1962) col. 10-13. Substantial increases in speed and contrast are not observed when direct positive emulsions containing the dyes employed herein are given low-temperature exposures.
  • the temperatures used in the practice of the invention are from about l 80 C. and below, such as down to the temperature of liquid helium, i.e., about 269 C.
  • Liquid air (l86 C.) or liquid nitrogen (l96 C.) can be conveniently used to lower the temperature of silver halide for the low-temperature exposure.
  • Emulsions which have been given low-temperature exposures in accordance with the invention are advantageously processed under conventional conditions, i.e., using standard developers and normal temperatures, such as above about 0 C. for example, up to about 50 C. and preferably at about room temperature or about 20 to 25 C.
  • the radiation to which the emulsions are exposed while held at a low-temperature can be any radiation to which the emulsions are inherently sensitive, i.e., radiation which the silver halide absorbs, or radiation which is absorbed by the spectral sensitizing dye. Exposures in just the region of absorption by the dye give approximately the same results as do exposures to just radiation to which the silver halide is sensitive.
  • EXAMPLE 1 A cubic grain emulsion is prepared according to the method described in Illingsworth et al. U.S. Pat. application Ser. No. 500,366 filed Oct. 21, 1965, and corresponding French Pat. No. 1,497,202 by adding an aqueous solution of potassium bromide and potassium iodide and an aqueous solution of silver nitrate in equal molar amounts simultaneously to a rapidly agitated aqueous gelatin solution maintained at a temperature of 70 C. the addition being carried out over a period of 35 minutes.
  • the pH of the aqueous gelatin solution is maintained at 2.0 by occasional additions of sulfuric acid and the pAg is maintained at 9.0 by adjusting the relative rates of addition of the halide and silver nitrate solutions.
  • the emulsion is washed and a protective colloid is added in the form of an aqueous gelatin solution.
  • the emulsion is coated on a cellulose acetate base.
  • the coating is exposed for 2 minutes, while immersed in liquid nitrogen (-1 96 C.), through a step wedge to a 1,000-watt tungsten lamp filtered by a combination of one Wratten 36 filter and one Wratten 38A filter (which filters limit the exposure to the region of inherent sensitivity of the silver halide) and operated at 2,650 K. at a distance of 80 cm. from the film.
  • the exposed film is then developed for 12 min. at 20 C. in a solution of N-methyl-p-aminophenol sulfate 2.5 g., ascorbic acid 10.0 g., sodium metaborate (Kodak Balanced Alkali) 35.0 g., potassium bromide 1.0 g., and water to make 1 liter.
  • the characteristic curve shown as curve 1 in FIG. 1, demonstrates the low sensitivity and contrast obtained at the low-temperature exposure.
  • Another strip of the same film is bathed in water for 20 min. at 21 C. dried, then exposed, developed, fixed, washed, and dried as before.
  • the characteristic curve, shown as curve 2 in FIG. 1, again illustrates the unsatisfactory sensitivity and response of the emulsion when exposed at low temperatures.
  • Another strip of the same film is bathed for 20 min. at 21 C.
  • EXAMPLE 2 Strips of the film coating described in example 1 are immersed in a 10* M solution of 1,1,3,3'-tetramethyl-2,2- cyanine p-toluenesulfonate or 3,3-diethylthiacarbocyanine ptoluenesulfonate for 20 min. at 21 C. (providing approximately monomolecular dye layer coverage of the silver halide) and then dried. Half of each strip is exposed at liquid nitrogen temperature and half is exposed in room air at 21 C. The strips are developed, fixed, washed, and dried as in example 1. In FIG.
  • curve 5 represents the characteristic curve for the part of the strip that had been immersed in the l,l,3,3- tetramethyl-2,2-cyanine p-toluene sulfonate and exposed at liquid nitrogen temperature (196 C.) and curve 7 represents the characteristic curve of the part of the strip that had been exposed at room temperature (21 C.
  • Curve 6 represents the characteristic curve for the part of the strip that had been immersed in the 3,3'-diethylthiacarbocyanine 3,3solution and exposed at liquid nitrogen temperature and curve 8 represents the characteristic curve of the part of the strip that had been exposed at room temperature.
  • Curve 2 is the control representing the film that had been bathed in water and exposed at liquid nitrogen temperature (see example 1). It is clear that the dyed film strips show only relatively small differences in threshold sensitivity between exposures at room temperature and at liquid nitrogen temperature. It is further evident that the contrast is higher for exposures at liquid nitrogen temperature than for exposures at room temperature.
  • EXAMPLE 3 Strips of the film coating described in example 1 are immersed in (strip ll) 10 M solution of l,l'-diethyl-2,4'- cyanine chloride, (strip 12) 10 M solution of 1,1 -dimethyl- 2,2'-cyanine p-toluene sulfonate, and (strip l3) 10 M solution of 1,1 -diethyl-2,2'-cyanine. Approximately monomolecular layer dye coverage is provided on the silver halide grains. The strips are exposed at liquid nitrogen temperature as in example 1, developed, fixed, washed, and dried. Characteristic curves, labeled ll, 12, and 13, are shown in FIG. 3.
  • the curve labeled 10 represents the undyed, control strip that had been immersed in water only. Curves labeled 10 and 13' represent samples of strips 10 and 13 that had been exposed at room temperature rather than liquid nitrogen temperature. It is clear that the dyed film strips show large increases in sensitivity and gamma over the undyed control strip for exposures at the temperature of liquid nitrogen. Moreover, the contrast of the dyed strips is greater for the liquid nitrogen temperature exposure than for a room temperature exposure of either dyed or undyed strips.
  • EXAMPLE 4 A fine grain, pure silver bromide emulsion is prepared and sulfur-sensitized with sodium thiosulfate. Coatings of this emulsion are immersed for 20 minutes in 10 M solutions of various dyes, then dried, exposed at liquid nitrogen temperature, developed, fixed, washed, and dried as described in example 1. Table 1 shows the speed and gamma values obtained.
  • the highest occupied electronic energy level of each dye adsorbed to the silver halide is more positive than the highest occupied energy level in the valence band of the silver halide
  • the lowest vacant electronic energy level of each dye adsorbed in the silver halide is more positive than the conduction band of the silver halide.
  • 1,1'-diethyl-2,2-cyanine has values of 5.53 ev. and 3.22 ev. for its highest occupied and lowest vacant electronic energy levels, and both of these values are more positive than the valence band (about -6.0 ev. relative to vacuum) and the conduction band (about 3.5 ev.) for silver halide.
  • Phenosafranine has a value of 6.l7 ev.
  • EXAMPLE 5 A cubic grain emulsion is prepared as in example 1, except that prior to coating 1,1-diethyl-2,2-cyanine chloride in the amount of 0.80 grams per mole of silver is added. This emulsion, when coated, exposed, and developed as in example 1,
  • h, m, n and p each represents an integer of from 1 to 2;
  • L represents a methine linkage;
  • R R and R each represents a member selected from the group consisting of an alkyl group and an aryl group;
  • R and R each represents an alkyl group containing from one to six carbon atoms;
  • X and X each represents an acid anion; and, Z Z and 2;, each represents the atoms necessary to complete a fiveto six-membered heterocyclic nucleus of the type used in methine dyes; said silver halide having a sufficient amount of said dye adsorbed thereto to effectively increase the speed of said silver halide when exposed at a temperature below about l C.

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3867146A (en) * 1970-12-14 1975-02-18 Fuji Photo Film Co Ltd Holographic reproduction using carbocyanine dye sensitized, fine-grain silver halide emulsions and neon-helium lasers
US3928856A (en) * 1970-09-16 1975-12-23 Fuji Photo Film Co Ltd Silver halide photographic emulsion for recording electron beam

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
Mees & James, The Theory of the Photographic Process, 3rd Ed. (the MacMillan Co., 1966) pages 19 21, 264 & 265 *
Toni et al., Cal. of Electronic Energy Levels of Photo Sensitizing Dyes PS&E, Vol. 11, No. 3, (1967) pages 129 144 *
West, Temperature-Dependence of Spectral Sensitization by Dye Series of Regularly Increased Chain Length and the Mechanism of Spectral Sensitization In PS&E, Vol. 6 (1962) page 92 101 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3928856A (en) * 1970-09-16 1975-12-23 Fuji Photo Film Co Ltd Silver halide photographic emulsion for recording electron beam
US3867146A (en) * 1970-12-14 1975-02-18 Fuji Photo Film Co Ltd Holographic reproduction using carbocyanine dye sensitized, fine-grain silver halide emulsions and neon-helium lasers

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