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(11) | EP 0 331 414 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Sensitizing dye for high chloride and low iodide silver halide photographic composition |
| (57) Dyes of the formula:
where R₁ is halogen, substituted or unsubstituted phenyl, or substituted or unsubstituted styryl, R₂ and R₃ are each independently substituted alkyl, substituted alkenyl, or substituted aryl that are substituted with an anionic solubilising group, Z represents the atoms necessary to complete a substituted or unsubstituted naphthyl ring, and X⁺ is a cation, are disclosed as sensitizing dyes for photographic compositions containing silver halide that is high in silver chloride content, low in silver iodide content, or both. |
[0001] This invention relates to photography, and specifically to spectral sensitization of silver halide emulsions that are low in iodide and/or high in silver chloride concentration.
[0002] Light-sensitive silver halide emulsions containing mainly silver bromide, e.g., silver bromoiodide or pure silver bromide, have been widely used in photographic compositions. Emulsions having a high silver chloride content (i.e., at least 80 mole percent silver chloride) have been considered desirable because they are capable of being processed more rapidly than silver halide emulsions having lower levels of silver chloride. With certain of such rapid photographic processes, it has also been found that the presence of significant amounts of iodide (i.e., greater than 1 mole percent) in the emulsion can inhibit development of the exposed silver halide.
[0003] A problem associated with implementing the use of high silver chloride emulsions has been insufficient speed in blue-sensitive emulsions. This is due to the lower intrinsic sensitivity to blue light of high silver chloride emulsions as compared to low silver chloride emulsions. Blue sensitizing dyes can be used to spectrally sensitize the silver chloride to blue light. Such dyes are described in EP 256,858 and U.S. 4,250,244. These dyes, however, still do not provide sufficient blue light sensitivity. It would thus be highly desirable to provide a blue sensitizing dye that imparts greater sensitivity to blue light in silver halide emulsions having either a high chloride content, a low iodide content, or both.
[0004] It has now been found that significantly improved sensitivity to blue light in high chloride or low iodide silver halide emulsions is provided by sensitizing dyes of the formula:
where R₁ is halogen, substituted or unsubstituted phenyl, or substituted or unsubstituted styryl,
R₂ and R₃ are each independently substituted alkyl, substituted alkenyl, or substituted aryl that are substituted with an anionic solubilising group,
Z represents the atoms necessary to complete a substituted or unsubstituted naphthyl ring, and
X⁺ is a cation.
[0005] The dyes of formula (I) provide high sensitivity to blue light in photographic compositions comprising silver halide that is high in silver chloride content, low in silver iodide content, or both.
[0006] According to formula (I), R₁ is halogen (e.g., Cl, F, or I), substituted or unsubstituted phenyl (e.g., phenyl, 4-chlorophenyl, 3-methylphenyl), or substituted or unsubstituted styryl (e.g., -CR=CR-0̸, where each R is independently H, or a substituent such as lower alkyl, and where the phenyl group may be substituted with substituents such as alkyl, halogen, alkoxy, and the like. In a preferred embodiment, R₁ is halogen, and in a more preferred embodiment, R₁ is fluoro or chloro.
[0007] Preferably, R₂ and R₃ are each independently substituted alkyl of from 1 to 6 carbon atoms having an anionic solubilising group substituent, (e.g., sulfoethyl, carboxypropyl, sulfatopropyl), substituted aryl of from 6 to 12 carbon atoms having an anionic solubilizing group substituent (e.g, p-sulfophenyl), or substituted alkenyl of from 3 to 10 carbon atoms having an anionic solubilizing group substituent (e.g, 2-carboxyallyl). More preferably, R₂ and R₃ are each independently substituted alkyl of from 1 to 6 carbon atoms having an anionic solubilizing group substituent. Anionic solubilizing groups as substituents on the nitrogen substituents of cyanine dyes are well-known in the art and include, for example, sulfo, carboxy, and sulfato, with sulfo being preferred.
[0008] Z represents the atoms necessary to complete a substituted or unsubstituted naphthyl ring. X⁺ is a cation such as sodium or triethylammonium. R₁, R₂, R₃, and Z may each be substituted with any of a number of known substituents, such as alkyl (e.g., methyl, ethyl, propyl, isobutyl, pentyl), alkenyl (e.g., allyl, carboxyethyl), aryl (e.g., phenyl, benzyl), alkoxy (e.g., methoxy, ethoxy), aryloxy (e.g., phenyloxy), halogen (e.g., fluro, chloro), hydroxy, cyano, and the like.
[0010] The amount of sensitizing dye of formula (I) that is useful in the invention is preferably in the range of 0.1 to 1.0 millimoles per pole of silver halide and more preferably from 0.2 to 0.7 millimoles per mole of silver halide. Optimum dye concentrations can be determined by methods known in the art.
[0011] The dyes of formula (I) can be synthesized by techniques known in the art, such as described in Hamer, Cyanine Dyes and Related Compounds, 1964 and James, The Theory of the Photographic Process 4th, 1977. Examples of the synthesis of representative dyes of formula (I) are set forth below.
[0012] The silver halide that the dyes of formula (I) advantageously sensitize is either high in chloride, low in iodide, or both. By high in chloride, it is meant that the silver halide comprises at least 80 mole percent silver chloride and preferably at least 95 percent silver chloride. By low in iodide, it is meant that the silver halide comprises no more than 1 mole percent silver iodide and preferably no more than 0.5 mole percent silver iodide.
[0013] The type of silver halide grain used in the invention is not critical and essentially any type of silver halide grains can be used in the practice of the invention. The grain size of the silver halide may have any distribution known to be useful in photographic compositions, and may be either polydisperse or monodisperse. The mean grain diameter is preferably from 0.05 µm to 1.5 µm.
[0014] The silver halide grains to be used in the invention may be prepared according to methods known in the art, such as those described in Research Disclosure, Item 17643, December, 1978 [hereinafter referred to as Research Disclosure I] and Mees, The Theory of the Photographic Process. These include methods such as ammoniacal emulsion making, neutral or acid emulsion making, and others known in the art. These methods generally involve mixing a water soluble silver salt with a water soluble halide salt in the presence of a protective colloid, and controlling the temperature, pAg, pH values, etc, at suitable values during formation of the silver halide by precipitation.
[0015] The silver halide to be used in the invention may be advantageously subjected to chemical sensitization with compounds such as gold sensitizers (e.g., aurous sulfide) and others known in the art. Compounds and techniques useful for chemical sensitization of silver halide are known in the art and described in Research Disclosure I and the references cited therein.
[0016] The silver halide may be sensitized by the dye of formula (I) by any method known in the art, such as described in Research Disclosure I. The dye may added to an emulsion of the silver halide grains and a hydrophilic colloid at any time prior to or simultaneous with the coating of the emulsion on a photographic element. The dye/silver halide emulsion may be mixed with a dispersion of color image-forming coupler immediately before coating or in advance of coating (e.g., 2 hours), although the latter is preferred as the dyes of formula (I) offer the advantage of good stability in silver halide/color image-forming coupler gelatin melts.
[0017] The dye of formula (I) may be used by itself to sensitize silver halide, or it may be used in combination with other sensitizing dyes to provide the silver halide with sensitivity to broader or different ranges of wavelengths of light than silver halide sensitized with a single dye or to supersensitize the silver halide.
[0018] In a preferred embodiment of the invention, the dye of formula (I) is used to sensitize silver halide in photographic emulsions, which can be coated as layers on photographic elements. Essentially any type of emulsion (e.g., negative-working emulsions such as surface-sensitive emulsions or unfogged internal latent image-forming emulsions, direct-positive emulsions such as surface fogged emulsions, or others described in, for example, Research Disclosure I) can be used.
[0019] Photographic emulsions generally include a vehicle for coating the emulsion as a layer of a photographic element. Useful vehicles include both naturally occurring substances such as proteins, protein derivatives, cellulose derivatives (e.g., cellulose esters), gelatin (e.g., alkali-treated gelatin such as cattle bone or hide gelatin, or acid treated gelatin such as pigskin gelatin), gelatin derivatives (e.g., acetylated gelatin), phthalated gelatin, and the like), and others as described in Research Disclosure I. Also useful as vehicles or vehicle extenders are hydrophilic water-permeable colloids. These include synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide copolymers, and the like, as described in Research Disclosure I. The vehicle can be present in the emulsion in any amount known to be useful in photographic emulsions.
[0020] The emulsion can also include any of the addenda known to be useful in photographic emulsions. These include chemical sensitizers, such as active gelatin, sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhenium, phosphorous, or combinations thereof. Chemical sensitization is generally carried out at pAg levels of from 5 to 10, pH levels of from 5 to 8, and temperatures of from 30 to 80°C, as illustrated in Research Disclosure, June, 1975, item 13452 and U.S. Patent 3,772,031.
[0021] Other addenda include antifoggants, stabilizers, filter dyes, light absorbing or reflecting pigments, vehicle hardeners such as gelatin hardeners, coating aids, dye-forming couplers, and development modifiers such as development inhibitor releasing couplers, timed development inhibitor releasing couplers, and bleach accelerators. These addenda and methods of their inclusion in emulsion and other photographic layers are well-known in the art and are disclosed in Research Disclosure I and the references cited therein.
[0022] The emulsion may also include brighteners, such as stilbene brighteners. Such brighteners are well-known in the art and are used to counteract dye stain, although many of the dyes of formula (I) (e.g., when R₁ is F) offer reduced dye stain when compared with other dyes.
[0023] The emulsion layer containing silver halide sensitized with the dye of formula (I) can be coated simultaneously or sequentially with other emulsion layers, subbing layers, filter dye layers, interlayers, or overcoat layers, all of which may contain various addenda known to be included in photographic elements. These include antifoggants, oxidized developer scavengers, DIR couplers, antistatic agents, optical brighteners, light-absorbing or light-scattering pigments, and the like.
[0024] The layers of the photographic element can be coated onto a support using techniques well-known in the art. These techniques include immersion or dip coating, roller coating, reverse roll coating, air knife coating, doctor blade coating, stretch-flow coating, and curtain coating, to name a few. The coated layers of the element may be chill-set or dried, or both. Drying may be accelerated by known techniques such as conduction, convection, radiation heating, or a combination thereof.
[0025] Photographic elements comprising the composition of the invention can be black and white or color. A color photographic element generally contains three silver emulsion layers or sets of layers: a blue-sensitive layer having a yellow color coupler associated therewith, a green-sensitive layer having a magenta color coupler associated therewith, and a red-sensitive layer having a cyan color coupler associated therewith. The photographic composition of the invention is advantageously utilized in a blue-sensitive layer of a color photographic element. These color image-forming couplers along with other element configurations are well-known in the art and are disclosed, for example, in Research Disclosure I.
[0026] Photographic elements comprising the composition of the invention can be processed in any of a number of well-known photographic processes utilizing any of a number of well-known processing compositions, described, for example, in Research Disclosure I or in James, The Theory of the Photographic Process 4th, 1977. Elements having high chloride silver halide photographic compositions are especially advantageously processed by fast processes utilizing a so-called rapid access developer, as described in Examples 1-3 below.
Synthesis Example 1 - Preparation of Dye I
[0028] A mixture of 16.5 g anhydro-5-fluoro-2-methyl-3-sulfopropylbenzothiazolium hydroxide, 19.5 g of anhydro-2-hydroxyiminomethyl-1-(3-sulfopropyl)-naphtho-[1,2-d]-thiazolium hydroxide, 412 ml dimethylformamide, and 7 ml acetic anhydride were heated to 60°C and 12 ml triethylamine were added. The mixture was heated to 90-95°C and then allowed to cool. The precipitate was filtered off, washed with dimethylformamide, acetone, and then ether, and then air dried to yield 28.8 g of crude dye 1.
[0029] The crude dye 1 was slurried in 325 ml boiling pyridine, and 42 ml of water was added. Precipitation occurred almost immediately. The mixture was cooled and filtered. The solid was washed with pyridine and then acetone, and air dried. 17.8 g of this product was slurried in 180 ml boiling pyridine, water (37 ml) was added, and the mixture was filtered. The filtrate was diluted to 300 ml with pyridine to cause precipitation and the mixture was boiled to coagulate the precipitate. The procedure was repeated for the resulting precipitate with 157 ml pyridine and 43 ml water with dilution to 350 ml with additional pyridine. The precipitate from the repeat procedure was filtered and dried to yield 14.3 g of dye 1, λ-max = 441 nm in methanol, ε = 7.38 X 10⁴.
Synthesis Example 2 - Preparation of Dye 2
[0030] A slurry of 27.8 g anhydro-2-hydroxyiminomethyl-1-(3-sulfopropyl )-β-naphthothiazolium hydroxide in 1.93 l of a 4:1 volumetric mixture of acetonitrile and water was heated to 70°C and 31 ml of acetic anhydride was added. This was followed by a solution of 24.0 g anhydro-5-chloro-2-methyl-3-sulfopropylbenzothiazolium hydroxide and 23.7 ml triethylamine in 967 ml of a 4:1 volumetric of acetonitrile and water, whereupon complete dissolution resulted. The reaction mixture was heated at reflux for 5 minutes and chilled. The clear supernatant was decanted through a filter funnel. The mushy solid was placed in 450 ml boiling acetonitrile to coagulate it and the hot mixture was filtered. The solid was washed with more hot acetonitrile and suction dried to yield 43.9 g. This solid was extracted with 700 ml boiling methanol and the extract was chilled and filtered. The resulting solid was dried at 60°C in a vacuum oven to yield 35.3 g of dye 2, λ-max = 444 nm in methanol, ε = 7.98 X 10⁴.
Examples 1-3
[0031] Dyes 1, 2, and 3, along with comparison dye A of the formula:
were each coated on a polyester support at 0.44 mmole/mole Ag in an aurous sulfide-sensitized silver chloride emulsion (0.7 µm diameter grains) having the following coverages:
The coupler dispersion was added to the dye/silver chloride emulsion immediately before coating. The elements also had a gel overcoat layer (1076 mg/m²) and undercoat layer (1076 mg/m²) above and below the emulsion layer.
[0032] The elements were exposed to either white light (3000°K tungsten light source with ultraviolet and heat-absorbing filters) or a light source designed to simulate a color negative print exposure source (3000°K tungsten light source with Wratten 65M and 140Y filters). The elements were then processed using a three-step operation of color development (45 sec, 35°C), bleach-fix (45 sec, 35°C) and stabilization or water wash (90 sec, 35°C) followed by drying (60 sec, 60°C).
The formulations for the above solutions are:
| 1) Color developer: | |
| Lithium salt of sulfonated polystyrene | 0.25 ml |
| Triethanolamine | 11.0 ml |
| N,N-diethylhydroxylamine (85% by wt.) | 6.0 ml |
| Potassium sulfite (45% by wt.) | 0.5 ml |
| Color developing agent (4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediaminesesquisulfate monohydrate) | 5.0 g |
| Stilbene compound stain reducing agent | 2.3 g |
| Lithium sulfate | 2.7 g |
| Potassium chloride | 2.3 g |
| Potassium bromide | 0.025 g |
| Sequestering agent | 0.8 ml |
| Potassium carbonate | 25.0 g |
| Water to total of 1 liter, pH adjusted to 10.12 | |
| 2) Bleach-fix: | |
| Ammonium sulfite | 58. g |
| Sodium thiosulfate | 8.7 g |
| Ethylenediaminetetraacetic acid ferric ammonium salt | 40. g |
| Acetic acid | 9.0 ml |
| Water to total 1 liter, pH adjusted to 6.2 | |
| 3) Stabilizer: | |
| Sodium citrate | 1 g |
| Water to total 1 liter, pH adjusted to 7.2 | |
[0033] The λ-max and relative speeds (normalized to the comparison dye) of the sensitized emulsion are set forth in Table I below:
Table I
| Dye | λ-max | White Light Speed | Printer Light Speed |
| A | 480 | 100 | 100 |
| 1 | 480 | 575 | 851 |
| 2 | 480 | 468 | 708 |
| 3 | 480 | 617 | 933 |
[0034] The results in Table I demonstrate the significantly higher speed of the emulsion having the dyes of formula (I) compared to the comparison dye. As a comparison, the dyes were used to sensitize silver bromoiodide (2.7% I) emulsions and no significant difference in speed was observed between the dyes of formula (I) and the comparison dye. Thus, the degree of speed increase observed in these Examples is not obtained in silver halide emulsions other than those having either high chloride content or low iodide content.
Examples 4-5
[0035] For comparison purposes, elements were prepared as in Examples 1-3 (except that the gelatin undercoat layer had 3076 mg/m²) with Dyes 1 and 2 of the invention and comparison dyes B, C, and D. Comparison dye C is compound 1-1 of EP 256,858 and comparison dye D is the dye of Example 5 of U.S. 4,250,244.
1. A photographic composition comprising silver halide of at least 80 mole percent
silver chloride or less than 1 mole percent silver iodide and a sensitizing dye of
the formula:
where R₁ is halogen, substituted or unsubstituted phenyl, or substituted or unsubstituted styryl,
R₂ and R₃ are each independently substituted alkyl, substituted alkenyl, or substituted aryl that are substituted with an anionic solubilising group,
Z represents the atoms necessary to complete a substituted or unsubstituted naphthyl ring, and
X⁺ is a cation.
where R₁ is halogen, substituted or unsubstituted phenyl, or substituted or unsubstituted styryl,
R₂ and R₃ are each independently substituted alkyl, substituted alkenyl, or substituted aryl that are substituted with an anionic solubilising group,
Z represents the atoms necessary to complete a substituted or unsubstituted naphthyl ring, and
X⁺ is a cation.
2. A photographic composition according to Claim 1 wherein R₁ is halogen.
3. A photographic composition according to Claims 1-2 wherein R₁ is chloro.
4. A photographic composition according to Claims 1-3 wherein R₁ is fluoro.
5. A photographic composition according to Claims 1-4, further comprising a color
dye-forming coupler.
6. A photographic composition according to Claim 5 wherein the dye forming coupler
is a yellow dye-forming coupler.
7. A photographic composition according to Claims 1-6, further comprising a hydrophilic
colloid.
8. A photographic composition according to Claims 1-7 wherein the silver halide comprises
at least 80 mole percent silver chloride.
9. A photographic composition according to Claims 1-8 wherein the silver halide comprises
less than 1 mole percent silver iodide.
10. A photographic element comprising a support having thereon a photographic composition
according to Claims 1-9.