DE68925924T2 - Photographic process - Google Patents

Description

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

Silver halide elements are normally subjected to some type of photographic processing after exposure to produce images suitable for viewing. Development generally involves contacting the element with a developer solution to produce a silver image corresponding to a latent image formed on the silver halide during exposure and further treating with a fixer solution to solubilize and remove silver halide not converted to silver during development. Any of a number of other known processing solutions may also be used, such as stop baths to stop image development, bleach solutions to remove silver already formed from the element, and a number of other known solutions (e.g., stabilizer baths, hardener solutions, wash baths, and the like).

The silver halide used in photographic elements is usually inherently sensitive only to blue light. Consequently, in order to provide sensitivity to light in other regions of the spectrum or to increase sensitivity to blue light, it is often desirable to spectrally sensitize the silver halide by adsorbing a sensitizing dye onto the silver halide, thereby imparting to the silver halide sensitivity to wavelengths of light through the adsorbed dye.

If photographic elements are processed with spectrally sensitized silver halide, the sensitizing dye may pass out of the element and enter one or more of the processing solutions. In fact, it is usually desirable to remove the sensitizing dye (usually in the fixer) from the element during the development process in order to minimize any adverse effects on image quality that may occur as a result of the sensitizing dye remaining in the element after development.

However, it has now been found that certain problems arise in situations where a large amount of sensitizing dye is present in a photographic element (e.g., at a concentration of 3.3 mg/m2) or when the level of replenishment of the processing solution or solutions is low, or both. Large amounts of sensitizing dye may be present due to 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 leaching out of the element and being dissolved in a processing solution, is removed from the element but not completely dissolved 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, producing visible spots or pustules on the image. They can also adhere to processing equipment, hinder the flow or mixing of processing solutions, and require costly and time-consuming cleaning procedures.

JP-A-62-166 335 describes the use of triazinylstilbene whitening agents to improve the whiteness, the precipitates produced in the presence of such compounds and a developer solution which Reduces precipitation. Research Disclosure No. 207, July 1981, page 268, describes the use of stilbene compounds to reduce discoloration caused by retained sensitizing dye.

It has now been discovered that the formation of solid dye particles in developing solutions can be reduced by a process which comprises contacting the element with a developing or processing solution which is sensitive 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, where at least two of the radicals R , R , R , R stand for

R₅ and R₆ are each independently hydrogen, substituted or unsubstituted alkyl or substituted or unsubstituted aryl, with the proviso that the dye-solubilizing compound has at least four solubilizing groups as substituents on the radicals R₅ or R₆, which are alkyl or aryl, with at least one of the solubilizing groups being an anionic sulfo group and M being a cation.

According to formula (I), R₁, R₂, R₃ and R₄ each independently represent

Halogen (e.g., fluoro, chloro, bromo, iodo), substituted or unsubstituted alkoxy of 1 to 6 carbon atoms (e.g., methoxy, ethoxy, propoxy). R5 and R6 are each independently hydrogen, substituted or unsubstituted alkyl of 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). Suitable substituents for the above R groups may include any of a number of substituents conventionally employed for such groups which 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, thioether etc.

For a compound of formula (I) to be useful in the invention it must have at least four solubilising groups as substituents on R₅ or R₆ and at least one of these solubilising groups must be an anionic sulpho group. These solubilising groups are groups which tend to increase the solubility of the organic compound in water. Such solubilising groups are well known in the art and include, for example, sulpho, carboxy and hydroxy groups. By an anionic sulpho group is meant an ionised -SOθ₃ group having an associated counter ion 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 sulpho group may be in the acid form prior to such contact. For example, if the dye solubilizing compound of formula (I) is used in conjunction with a developing solution having 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 ionizes the sulfo group.

From the requirement that the compound of formula (I) has four solubilizing groups as substituents on the radicals R₅ or R₆, it can be concluded that at least two of the radicals R₁, R₂, R₃ or R₄ must represent

The solubilizing groups include any groups whose presence as a substituent on the compound of formula (I) results in it being more soluble in aqueous solutions than without a substituent.

Examples of suitable compounds according to formula (I) are listed below in Table I. TABLE I Connection

The compounds of formula (I) can be prepared by methods known in the art. Such methods are described, for example, in 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 into any processing or developing solution in which the sensitizing dye is present in the solution in a concentration sufficient to result in the formation of solid dye particles in the absence of the dye solubilizing compound. Alternatively, the dye solubilizing compound can be incorporated into the photographic element so that the dye solubilizing compound is present when the element is contacted with the solution sensitive to dye particle formation. The developing or processing solution can contain, for example, 0.01 to 1.0 g of cyanine dye/l. The amount of dye solubilizing compound in the developing or processing solution can be, for example, 0.1 to 10 g/l.

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

The sensitizing cyanine dye can be any of a number of such dyes which are well known in the art. The spectral sensitizing cyanine dyes have two basic heterocyclic nuclei linked together by a methine bond, such as: B. those derived from quaternary quinolinium, pyridinium, isoquinolinium, 3H-indolium, benz[e]indolium, oxazolium, thiazolium, selenazolinium, imidazolium, benzoxazolinium, benzothiazolium, benzoselenazohum, benzimidazolium, naphtoxazolium, naphtothiazolium, napthoselenazolium, thiazolinium, dihydronaphthothiazolium, pyrylium and imidazopyrazinium salts. A further description and examples of such dyes can be found in the book by James, The Theory of the Photographic Process, 4th edition, 1977 and in the reference Research Disclosure, December 1978, No. 17643 (hereinafter referred to as "Research Disclosure I").

Suitable cyanine dyes include those according to the formula:

In this formula, Z₁ and Z₂ represent the atoms required to complete a substituted or unsubstituted aromatic ring structure. R₇ and R₈ each independently represent substituted or unsubstituted alkyl having 1 to 12 carbon atoms (e.g., methyl, ethyl, propyl, butyl). R₇ and R₈ may be substituted by substituents 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 such as alkyl) or unsubstituted methine bonds. 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 may contain any type of silver halide suitable for photographic emulsions. These include silver bromide, silver iodide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, or mixtures thereof. The silver halide may 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 may be present in any amount known in the art to be suitable for photographic emulsions. The silver halide is generally present in the emulsion in an amount such that when it is present as a layer in a photographic element, the silver coating thickness is from 1.1 to 3.2 g/m².

The amount of sensitizing dye in the emulsion may be any amount known in the art to be suitable for spectral sensitization of silver halide and subject to the requirement that it be sufficient to prevent the formation of solid dye particles in a solution for development of the element. The amount of dye used varies with the particular dye or combination of dyes selected, as well as the size and aspect ratio of the grains. It is known in the photographic art that optimum spectral sensitization is generally achieved with organic dyes at 25 to 100% monolayer coverage of the total available surface of the surface-sensitive silver halide grains, as described, for example, in West et al., "The Adsorption of Sensitizing Dyes in Photographic Emulsions," Journal of Phys. Chem., Vol. 56, page 1065, 1952, and by Gilman et al., U.S. Patent 3,979,213. Optimum dye concentration levels can be selected by methods described by Mees, Theory of the Photographic Process, Macmillan Publishers (1942), pages 1067-69. Preferred amounts of dye in photographic elements useful in the present invention are from 1.1 to 10.8 g/m².

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

The emulsion preferably contains a vehicle for coating the emulsion in the form of a layer of a photographic element. Suitable 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 bovine 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 suitable as carriers or carrier extenders are hydrophilic water permeable colloids. These include synthetic polymeric peptizers, carriers and/or binders such as. B. 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 suitable for photographic emulsions.

The silver halide emulsion may further comprise any of the additives known to be useful in photographic emulsions. These include chemical sensitizers such as active gelatin, sulfur, selenium, tellurium, gold, platinum, palladium, iridium, osmium, rhenium, phosphorus, or combinations thereof. Chemical sensitization is generally carried out at pAg values of 5 to 10, pH values of 5 to 8, and temperatures of 30 to 80°C, as illustrated in Research Disclosure, June 1975, Item 13452 and in U.S. Patent 3,772,031.

Other additives include optical brighteners, antifogging agents, stabilizers, filter dyes, light absorbing or reflecting pigments, carrier hardeners such as gelatin hardeners, coating aids, dye-forming couplers and developing Modifiers such as development inhibitor releasing couplers and bleach accelerators. These additives and methods of introducing them into the emulsion are well known in the art and are described in Research Disclosure I and the references cited herein.

The emulsion layer and other layers of the photographic elements can be coated on a support by methods well known in the art. These methods include immersion or dip coating, roll 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 additives known to be useful in photographic elements such as antifoggants, oxidized developer scavengers, DIR couplers, antistatic compounds, optical brighteners, light absorbing or light scattering pigments and the like. The coated layers of the photographic element can be fixed or dried by cooling or subjected to both processes. Drying can be accelerated by known techniques such as conduction, convection, radiant heating or a combination thereof.

The photographic element useful in the practice of the invention may be a black-and-white element or a color element. Certain black-and-white elements having a moderately high density in image areas, a minimum density in non-image areas and require sufficient contrast to produce images with high quality resolution (e.g., in the case of microfilm or microfiche elements), contain sufficient amounts of silver halide (i.e., 1.1 to 2.2 g/m²) so that when sensitized with a cyanine dye, the amount of cyanine dye is sufficient to result in dye particle formation in the processing solution. A color photographic element generally comprises three silver halide emulsion layers: a blue-sensitive layer having associated therewith a yellow color-forming coupler, a green-sensitive layer having associated therewith a magenta color-forming coupler, and a red-sensitive layer having associated therewith a cyan color-forming coupler.

The compound of formula (I) can be used in conjunction with virtually any known process, the precise type of process not being critical. Such processes generally involve contacting the element with an aqueous alkaline solution of a developing agent and then contacting the element with a solution of a fixing agent or with bleaching and fixing agents. Examples of developing compositions and techniques are described by L. Mason in 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 in Neblette's Handbook of Photography and Reprography Materials, Processes and Systems, Vannostrand Reinhold Co., 7th Edition, 1977.

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

Developer solutions generally have a pH of 9 or above, although this is not a requirement of the invention. The use of the compound of formula (I) in an alkaline developer solution as indicated above allows for the ionization of any acidic solubilizing sulfo group of the compound. The developer agent may be any of the known developer agents as described in James, The Theory of the Photographic Process, 4th Edition, Macmillan Publishers, 1977 [hereinafter referred to as "James"], Chapter 11. Suitable developer agents include hydroquinones, catechins, aminophenols, pyrazolidones, phenylenediamines, tetrahydroquinolines, bis(pyridone)amines, cycloalkenones, pyramidines, reductones and coumarins.

Fixing agents are also known in the art and are described, for example, in James, Chapter 15. Suitable 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 and ammonium thiosulfate, are among the most commonly used fixing agents.

Other solutions commonly used in the processing of photographic elements which may also contain a compound of formula (I) include washing baths consisting primarily of water and optionally containing pH buffers or other stabilizers, bleaching or bleach/fixing solutions, color developing solutions (which may or may not contain photographic couplers), stop baths for terminating photographic development, gelatin hardening solutions and other known photographic processing solutions. All of these solutions and Process steps are well known from the state of the art.

The invention is further illustrated by the following examples.

EXAMPLE 1

A photographic element was prepared with an emulsion layer containing gelatin in a coating thickness of 1.56 g/m² and silver bromide in a coating thickness of 1.61 g/m², sensitized with a dye of the formula:

at a coating thickness of 5.4 mg/m². Element samples were developed in a semi-continuous batch process, with the element being successively transferred from one tank to the next containing well-mixed, unreplenishable processing solutions. The tanks were set up as shown in Table II below: TABLE II Tank Components (Concentrate g/l) Volume (Gal) Treatment Time Developer Hydroquinone (45) Monomethyl-p-aminophenolsulfonate as for 1 Fixer Ammonium thiosulfate Wash

After 4.6 m² had been developed, a number of visible dye particles had formed in the solutions of tanks 2 and 3.

The semi-continuous batch procedure was repeated except that tanks 1 and 2 also contained 0.5 g of Compound 5 from Table I/1. After 18.6 m² of film had been developed, no dye particles could be detected in any of the tanks.

The semi-continuous batch procedure was repeated again except that tank 3 contained 0.5 g/l of compound 5 of Table I instead of tanks 1 and 2. After 9.3 m2 of film had been developed, no dye particles could be detected in any of the tanks.

EXAMPLE 2

The effect of dye solubilizing compounds according to formula (I) of Table 1 on various dyes in different processing solutions was determined by the following procedure.

To 0.1 L of the room temperature developer (D) or fixer (F) solutions of the compositions of Example 1, with and without (as indicated in Table IV) 50 mg of the dye solubilizing compound of Table I, was added 5 mg of dyes D-1, D-2 or D-3. Control compounds as indicated in Table III were also tested as dye solubilizing compounds. The formation of dye particles was then determined by visual observation. The results are summarized in Table IV. TABLE III Connection TABLE IV Dye solubilizing compound Solution Dye Solubility without (comparison) TABLE IV (continued) Dye Solubilizing Compound Solution Dye Solubility S = Soluble (No particles observed) I = Insoluble (Many particles observed)

* Dye particle formation was also observed at lower dye concentrations around 0.01 g/l.

The results, which are summarized in Table IV, show that the compounds according to formula (I) are considerably better dye solubilizing compounds than the comparative compounds.

Claims (11)

1. A process for developing a photographic element comprising a layer containing a silver halide emulsion sensitized with a cyanine dye, which comprises contacting the element with at least one developing solution, characterized in that the solution contains a dye-solubilizing compound of the following formula: wherein: R₁, R₂, R₃ and R₄ each independently represent a radical of the formula Halogen, hydrogen, hydroxy, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted alkoxy or sulfo, where at least two of the radicals R₁, R₂, R₃ and R₄ are R�5 and R�6 each independently represent hydrogen, substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that the a dye-solubilizing compound has at least four solubilizing groups as substituents on R₅ or R₆ radicals, which are alkyl or aryl radicals, wherein at least one of the solubilizing groups is an anionic sulfo group, M a cation, and wherein the cyanine dye is present in the developing solution in a concentration sufficient to cause the formation of solid dye particles in the absence of the dye solubilizing compound. 2. Process according to claim 1, characterized in that the developing solution is a photographic developer solution. 3. A method according to claim 1, wherein the developing solution is a photographic fixing solution. 4. Process according to claims 1-3, wherein the dye corresponds to the following formula: wherein: Z�1 and Z₂ represent the atoms required to complete a substituted or unsubstituted aromatic ring structure, R�7 and R⁸ each independently represent substituted or unsubstituted alkyl, L₁, L₂ and L₃ each independently represent substituted or unsubstituted methine bonds, X stands for O, S, Se, -C- or N-, and n is equal to 0, 1 or 2. 5. A process according to claims 1-4, wherein the photographic element is a black and white element. 6. Process according to claims 1 - 5, in which the developing solution contains 0.01 to 1.0 g/l of the cyanine dye. 7. Process according to claims 1-6, wherein the solution contains 0.1 to 10 g/l of the dye-solubilizing compound. 8. Process according to claims 1 - 7, wherein R₁, R₂, R₃ and R₄ each independently represent wherein each of R₅ and R₆ independently represents substituted or unsubstituted alkyl or substituted or unsubstituted aryl, provided that R₁, R₂, R₃ and R₄ together contain at least five solubilizing groups, at least one of which is an anionic sulfo group. 9. Process according to claims 1-8, in which the solubilizing groups are sulfo, hydroxy or carboxy groups. 10. Process according to claims 1-9, wherein the cyanine dye is present in the developing solution in a concentration sufficient to cause the formation of solid dye particles having an average diameter of at least 0.3 µm in the absence of the dye-solubilizing compound. 11. Method according to claims 1 - 10, in which R₁ and R₃ each represent wherein R₉ and R₁₀ each independently represent hydroxy-substituted alkyl having 1 to 6 carbon atoms, and wherein R₂ and R₄ each independently represent wherein R₁₁ is sulfo-substituted aryl having 6 to 10 carbon atoms.