This invention relates to photography, especially photographic processes for elements having silver halide sensitized with a cyanine dye.

Silver halide elements are usually subjected to some type of photographic processing after exposure in order to form images suitable for viewing. The processing generally involves contacting the element with a developer solution to cause formation of a silver image corresponding to a latent image formed on the silver halide during exposure, and then with a fixing solution to solubilize and remove silver halide that was not converted to silver during development. Any of a number of other known processing solutions may also be used, such as stop baths to halt image development, bleach solutions to remove already formed silver from the element, and a number of other known solutions (e.g., stabilizer baths, hardener solutions, wash baths, and the like).

The silver halide that is used in photographic elements is usually inherently sensitive only to blue light. It is therefore often desirable, in order to provide sensitivity to light of other regions of the spectrum or to enhance the sensitivity to blue light, to spectrally sensitize the silver halide by adsorbing a sensitizing dye to the silver halide, thus imparting to the silver halide sensitivity to the wavelength of light absorbed by the dye.

When photographic elements having spectrally sensitized silver halide are processed, the sensitizing dye can come out of the element and enter one or more of the processing solutions. Indeed, it is usually desirable to remove (usually in the fixing bath)the sensitizing dye from the element during processing so as to minimize adverse effects on image quality that can occur as a result of sensitizing dye remaining in the element after processing.

It has now been found, however, that certain problems are encountered in situations where a large amount of sensitizing dye is present in a photographic element (e.g., at a level of 3.3 mg/m), or when the rate of replenishment of the processing solution(s) is low, or both. Large amounts of sensitizing dye may be present because of the particular sensitization of silver halide that is desired, or simply because an element contains a large amount of silver halide. In such situations, the sensitizing dye, instead of coming out of the element and dissolving in a processing solution, is removed from the element, but is not fully solubilized in the processing solution and forms solid particles. These particles can have a number of adverse effects. They can adhere to the surface of the element, forming visible specks or blotches on the image. They can also adhere to processing equipment, impeding flow or mixing of processing solutions, and necessitating costly and time-consuming cleaning procedures.

JP-A-62-166 335 describes the use of triazinyl stilbene whitening agents to improve whiteness, the precipitates that are produced in the presence of such compounds, and a developer solution which reduces precipitate formation. Research Disclosure No. 207, July 1981, p. 268 describes the use of stilbene compounds to reduce retained sensitizing dye stain.

It has now been found that the formation of solid dye particles in processing solutions can be reduced by a process where the the element is contacted with a processing solution that is susceptible to dye particle formation in the presence of an effective amount of a dye solubilizing compound of the formula:    wherein R₁, R₂, R₃, and R₄ are each independently halogen, hydrogen, hydroxy, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkoxy, or sulfo, at least two of R₁, R₂, R₃, R₄ being R₅ and R₆ are each independently hydrogen, substituted or unsubstituted alkyl, or substituted or unsubstituted aryl, with the proviso that the dye solubilizing compound comprises at least four solubilizing groups as substituents on R₅'s or R₆'s that are alkyl or aryl wherein at least one of the solubilizing groups is anionic sulfo, and M is a cation.

According to formula (I), R₁, R₂, R₃, and R₄ are each independently halogen (e.g. fluoro, chloro, bromo, iodo), substituted or unsubstituted alkoxy of from 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy). R₅ and R₆ are each independently hydrogen, substituted or unsubstituted alkyl of from 1 to 7 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, t-butyl, n-hexyl, etc.), or substituted or unsubstituted aryl (e.g., phenyl, naphthyl, and the like). Useful substituents for the above R groups can include any of a number of substituents commonly utilized for such groups that do not adversely affect the properties of the compound to a significant degree. Examples of such substituents include halogen, alkyl, aryl, and alkoxy as described above, as well as other known substituents, such as allyl, thioethers, etc. . . .

For a compound of formula (I) to be useful according to the invention, it must have at least four solubilizing groups as substituents on R₅'s or R₆'s and at least one of those solubilizing groups must be anionic sulfo. These solubilizing groups are groups that tend to increase the solubility of organic compounds in water. Such solubilizing groups are well-known in the art and include, for example, sulfo, carboxy, and hydroxy. By anionic sulfo is meant an ionized -SO$\frac{\text{θ}}{\text{3}}$ group associated with a counterion, as opposed to an acidic -SO₃H group. It should be noted that since the invention requires contact of the photographic element in the presence of a compound of formula (I), the sulfo group may be in acid form prior to such contact. For example, if the dye solubilizing compound of formula (I) is being used in conjunction with a developer solution with a high pH (usually 9 or above), then the solubilizing group may be an acidic -SO₃H group until contact with the developing solution, at which time the high pH would ionize the sulfo group.

Clearly, by inference from the requirement that the compound of formula (I) comprise four solubilizing groups as substituents on R₅'s or R₆'s, at least two of R₁, R₂, R₃, or R₄ must be The solubilizing groups include any group whose presence as a substituent on the compound of formula (I) will tend to render it more soluble in aqueous solutions than without it.

Examples of useful compounds according to formula (I) are presented below in Table I.

The compounds of formula (I) can be made by methods well-known in the art. Such methods are described in, for example, U.S. Patents 3,617,295, 3,615,641, 2,937,089, and 3,615,632.

The dye solubilizing compound of formula (I) can be incorporated in any processing solution where the sensitizing dye would be present in the solution at a concentration sufficient to cause formation of solid dye particles in the absence of the dye solubilizing compound. Alternatively, the dye solubilizing compound can be incorporated in the photographic element so that the dye solubilizing compound is present when the element is contacted with the solution that is susceptible to dye particle formation. The processing solution may for example, have from 0.01 to 1.0 g/l of the cyanine dye. The amount of dye solubilizing compound in the processing solution may, for example, be from 0.1 to 10g/l

The compound of formula (I) can be used in conjunction with any combination of photographic element and process that is susceptible to formation of solid particles of cyanine sensitizing dye in any of the processing solutions.

The cyanine sensitizing dye can be any of a number of such dyes, which are well-known in the art. The cyanine spectral sensitizing dyes include, joined by a methine linkage, two basic heterocyclic nuclei, such as those derived from quinolinium, pyridinium, isoquinolinium, 3H-indolium, benz[e]indolium, oxazolium, thiazolium, selenazolinium, imidazolium, benzoxazolinium, benzothiazolium, benzoselenazolium, benzimidazolium, naphthoxazolium, naphthothiazolium, naphthoselenazolium, thiazolinium dihydronaphthothiazolium, pyrylium, and imidazopyrazinium quaternary salts. Further description and examples of such dyes can be found in James, The Theory of the Photographic Process 4th, 1977 and in Research Disclosure, December, 1978, item 17643 (hereinafter referred to as "Research Disclosure I").

Useful cyanine dyes include those according to the formula:

In this formula, Z₁ and Z₂ represent the atoms necessary to complete a substituted or unsubstituted aromatic ring structure. R₇ and R₈ are each independently substituted or unsubstituted alkyl of 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, butyl). R₇ and R₈ may be substituted with substituents as is known in the art, such as halogen, alkoxy, aryl, aryloxy, sulfo, carboxyl, and the like). L₁, L₂, and L₃ are each independently substituted (with substituents known in the art, e.g., alkyl) or unsubstituted methine linkages. X is O, S, Se, -C-, or N- and n is 0, 1, or 2.

Photographic elements useful in the practice of the invention generally comprise a support having thereon at least one silver halide emulsion layer. The silver halide emulsion can comprise any type of silver halide that is useful in photographic emulsions. This includes silver bromide, silver iodide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The silver halide can be in the form of grains bounded by 100, 111, or 110 crystal planes, as described in Research Disclosure I, or in the form of tabular grains, as described in Research Disclosure, January, 1983, item 22534. The silver halide can be present in any amount known in the art to be useful in photographic emulsions. The silver halide is generally present in the emulsion in an amount such that when it is coated as a layer in a photographic element, the coverage of silver will be from 1.1 to 3.2 g/m.

The amount of sensitizing dye in the emulsion can be any amount that is known in the art to be useful for spectral sensitization of silver halide, subject to the requirement that it be sufficient to cause formation of solid dye particles in a solution for processing the element. The quantity of dye employed will vary with the specific dye or dye combination chosen as well as the size and aspect ration of the grains. It is known in the photographic art that optimum spectral sensitization is generally obtained with organic dyes at 25 to 100 percent of monolayer coverage of the total available surface area of surface sensitive silver halide grains, as disclosed for example, in West et al, "The Adsorption of Sensitizing Dyes in Photographic Emulsions," Journal of Phys. Chem., Vol. 56, p. 1065, 1952 and Gilman et al U.S. Patent 3,979,213. Optimum dye concentration levels can be chosen by procedures taught by Mees, Theory of the Photographic Process, Macmillan (1942), pp. 1067-69. Preferred dye amounts in photographic elements useful according to the present invention range from 1.1 to 10.8 g/m.

One or more spectral sensitizing dyes may be used to achieve a desired spectral sensitization of the silver halide as well as to achieve results such as supersensitization, as discussed by Gilman in Photographic Science and Engineering, Vol. 18, 1974, pp. 418-30. Examples of supersensitizing dye combinations include those disclosed in Mcfall et al U.S. Patent 2,933,390, Jones et al U.S. Patent 2,937,089, Motter U.S. Patent 3,506,443, and Schwan et al U.S. Patent 3,672,898.

The emulsion preferably includes 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), polysaccharides (e.g., dextran, gum arabic, casein, pectin, 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.

The silver halide 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.

Other addenda include brighteners, 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 and bleach accelerators. These addenda and methods of inclusion in the emulsion are well-known in the art and are disclosed in Research Disclosure I and the references cited therein.

The emulsion and other layers of photographic elements 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.

The silver halide emulsion layer of the photographic element can be coated simultaneously or sequentially with other emulsion layers, subbing layers, filter dye layers, or interlayers or overcoat layers containing various addenda known to be included in photographic elements, such as antifoggants, oxidized developer scavengers, DIR couplers, antistatic agents, optical brighteners, light-absorbing or light-scattering pigments, and the like. The coated layers of the photographic 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.

The photographic element useful in the practice of the invention can be black and white or color. Certain black and white elements requiring moderately high density in imaged areas, minimum density in non-imaged areas, and sufficient contrast to yield high quality definition images (e.g., microfilm or microfiche elements), contain sufficient amounts of silver halide (i.e., 1.1 to 2.2 g/m) so that when they are sensitized with a cyanine dye, the amount of cyanine dye is sufficient to cause dye particle formation in processing solutions. A color photographic element generally contains three silver halide emulsion 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 compound of formula (I) can be used in conjunction with essentially any known process, the exact type of which is not critical. Such processes generally include contacting the element with an aqueous alkaline solution of a developing agent, and then contacting the element with a solution of fixing agent or with bleaching and fixing agent(s). Examples of processing formulations and techniques are described in L. Mason, Photographic Processing Chemistry, Focal Press, London, 1966; Processing Chemicals and Formulas, Publication J-1, Eastman Kodak Company, 1985; Photo-Lab Index, Morgan & Morgan, Inc., Dobbs Ferry, New York, 1977; and Neblette's Handbook of Photography and Reprography Materials, Processes and Systems, VanNostrand Reinhold Co., 7th Ed., 1977.

The compound of formula (I) can be incorporated in the element or in any processing solution in which solid dye particle formation is a problem. When the compound is to be included in a processing solution, it is preferably incorporated in a developing solution or a fixing solution.

Developing solutions generally have a pH of 9 or more, although that is not a requirement of the invention. The use of the compound of formula (I) in an alkaline developing solution, as indicated above, does allow for ionization of any acidic sulfo solubilizing groups on the compound. The developing agent can be any of the known developing agents, as described in James, The Theory of the Photographic Process, 4th, Macmillan, 1977 [hereinafter "James"], Chapter 11. Useful developing agents include hydroquinones, catechols, aminophenols, pyrazolidones, phenylenediamines, tetrahydroquinolines, bis(pyridone)amines, cycloalkenones, pyramidines, reductones, and coumarins.

Fixing agents are also known in the art, as described in James, Chapter 15. Useful fixing agents include thiosulfates, thiocyanates, cyanides, sulfite, ammonia, thiourea, thioacids, thiosugars, concentrated alkali halides, and organic solvents such as acetone. Thiosulfates, such as sodium thiosulfate or ammonium thiosulfate are among the most commonly-used fixing agents.

Other solutions commonly used in the processing of photographic elements, which may also include a compound of formula (I), include wash baths consisting primarily of water and optionally pH buffers or other stabilizers, bleach or bleach/fix solutions, color developer solutions (which may or may not contain photographic couplers, stop baths for arresting photographic development, gelatin hardening solutions, and other known photographic processing solutions. All these solutions and processing steps are well-known in the art.

The invention is further illustrated by the following examples.

A photographic element was prepared, having an emulsion layer containing gelatin at a coverage of 1.56 g/m and silver bromide at a coverage of 1.61 g/m sensitized with a dye of the formula: at a coverage of 5.4 mg/m. Samples of the element were processed in a semicontinuous batch process in which the element moves successively from one tank to the next of well-mixed non-replenished processing solutions. The tanks were set up as described in Table II below: Tank Components (level-g/l) Volume (gal) Processing Time 1 Developer hydroquinone (45) 0.5 (1.93 l) 15 sec momomethyl-p-amino-phenolsulfonate (12.5) NaSO₃ (140) NaBr (2.5) pH = 10.9 2 same as 1 0.5 (1.93 l) 15 sec 3 Fixer ammonium thiosulfate (140) 0.5 (1.93 l) 15 sec NaSO₃ (25) pH = 5.0 4 Wash 0.5 (1.93 l) 15 sec 5 Wash 0.5 (1.93 l) 15 sec

After 4.6 m had been processed, a number of visible dye particles had formed in the solutions of Tanks 2 and 3.

The semicontinuous batch was repeated except that tanks 1 and 2 also contained 0.5 g/l of compound 5 from Table I. After 18.6 m of film had been processed, no dye particles were observed in any of the tanks.

The semicontinuous batch was again repeated except that tank 3 instead of tanks 1 and 2 contained 0.5 g/l of compound 5 from Table I. After 9.3 m of film had been processed, no dye particles were observed in any of the tanks.

The effect of dye solubilizing compounds according to formula (I) from Table I on varying dyes in varying processing solutions was evaluated according to the following procedure.

To 0.1 l of room temperature developer (D) or fixer (F) solutions of the formulations in Example 1, containing or not containing (as indicated in Table IV) 50 mg of Table I dye solubilizing compound, 5 mg of dyes D-1, D-2, or D-3 were added. Comparison compounds as shown in Table III were also tried as dye solubilizing compounds. The formation of dye particles was then determined by visual observation. The results are set forth in Table IV.

The results presented in Table IV indicate that compounds according to formula (I) are significantly better dye solubilizing compounds than the comparison compounds.