Classifications

• • 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
  • G03C1/14—Methine and polymethine dyes with an odd number of CH groups
  • G03C1/16—Methine and polymethine dyes with an odd number of CH groups with one CH group
• • 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
  • G03C1/061—Hydrazine compounds

Definitions

• This invention relates to negative acting silver halide photographic materials capable of producing high contrast silver images.
• the invention relates to high contrast photographic materials having a reduced propensity to formation of pepper fog which are also handleable under bright amber safelight conditions.
• black-and-white photographic images formed by a combination of maximum density areas and minimum density areas e.g. half tone imaging.
• a contrast of at least 10 herein referred to as high contrast
• An example of high contrast photographic elements having white reflective supports are phototypesetting materials intended to produce black type character images on the white background.
• An example of high contrast photographic elements having transparent supports are lith films, so called because they are used as contact transparencies for exposing lithographic printing plates. The illusion that some areas of a printed image are of intermediate density is created by the viewer's inability to resolve tiny dots of maximum density and background areas of minimum density that separate them.
• hydrazines in the developer and/or photographic elements of high contrast systems to increase speed and contrast is well known and disclosed, for example, in British Patent No. 598108, United States Patents 2322027, 2419974, 2419975, 4166742, 4211857, 4224401, 4243739, 4272606, 4272614, 4311781 and 4323643 and in Research Disclosure, Vol. 235, November 1983, Item 23510.
• Pepper fog differs from ordinary fog in that it takes the form of small, maximum density areas randomly distributed on a substantially uniform minimum density background.
• a photographic element exhibiting pepper fog is viewed under magnification the impression to the viewer is often that the magnified field of view has been sprinkled with grains of pepper.
• Pepper fog is a well recognised problem in high contrast photographic systems and provides a serious problem to the photographic printing plate making process.
• These black spots are tiny black specks which appear in the area between dots that is not intended to be developed and tend to increase and grow on ageing of the photographic material and particularly during storage thereof under high temperature, high humidity conditions, or as the concentration of the sulphite ion used commonly as a preservative in the developer decreases or as the pH value of the solution increases.
• the formation of black peppers detracts considerably from the marketability of the product as a photographic material for manufacturing a photographic printing plate.
• United States Patent Specification No. 4618574 discloses a negative working photographic element capable of producing a high contrast silver image.
• the element comprises surface latent image forming monodispersed silver halide grains having a mean diameter of less than 0.7 microns a contrast enhancing arylhydrazide, and, in an amount sufficient to reduce pepper fog while maintaining high contrast, a polyhydroxybenzene and a carboxyalkyl-3H-­thiazoline-2-thione.
• European Patent Publication No. 0196626 discloses a silver halide photographic material comprising a support, at least one silver halide emulsion layer and one or more light-insensitive hydrophilic colloid layers, wherein said silver halide emulsion layer or said light-insensitive hydrophilic colloid layer contains a hydrazine derivative, and the photographic material has a film surface pH not higher than 5.8 on the side of said emulsion layer inclusive of said light-insensitive hydrophilic colloid layer.
• the formation of pepper fog is reduced by maintaining the pH of the film surface on the side of the emulsion layer to not more than 5.8.
• U.S. Patent Specification No. 4,272,606 discloses the construction of a photographic material having high contrast and lower pepper fog which contains a hydrazine together with a compound containing a thioamido moiety in the molecule, included within this class are molecules containing the rhodanine and thiohydantoin nucleus.
• European Patent Publication No. 0285308 discloses the use of water-soluble bromide and chloride compounds e.g. alkali metal chlorides or bromides, added to a high contrast silver halide photographic emulsion in association with a hydrazine as a way of controlling pepper fog and increasing contrast.
• water-soluble bromide and chloride compounds e.g. alkali metal chlorides or bromides
• the sensitivity of materials which are handleable in bright amber light conditions must be such that the sensitivity to electromagnetic radiation does not extend much beyond 540nm.
• the natural sensitivity of silver halide emulsions is such that they meet the criteria, for example silver chloride absorbs little radiation above 440nm, silver bromide above 500nm and a typical iodobromide emulsion shows little sensitivity to radiation above 540nm.
• a photographic element capable of producing a high contrast silver image comprising a high contrast negative-acting silver halide photographic emulsion in association with a hydrazine characterised in that the emulsion is additionally associated with a monomethinebenzthiazole compound having a nucleus of the general formula: in which: one of R1 and R2 represents an organic group containing an acid function and the other is selected from hydrogen, an optionally substituted alkyl group and an organic group containing an acid function.
• benzthiazole cyanine dyes are well known as spectral sensitisers for silver chlorobromide or bromide emulsions, heretofore they have not been used as pepper fog controllers in hydrazine containing systems.
• Canadian Patent No. 1146001 and U.S. Patent No. 4618574 disclose a list of useful spectral sensitising compounds for high contrast hydrazine containing materials.
• the preferred compounds are said to be cationic cyanine and merocyanine dyes and are generally ortho and panchromatic sensitisers. There is no disclosure of the compounds of formula (I).
• U.S. Patent No. 2410690 relates to a combination of a hydrazine derivative and a cationic onium compound such as cyclammonium quaternary salts or sulphonium salts to give improved speed and contrast in photographic emulsion.
• This Patent gives examples of the ways in which such a system may be spectrally sensitised particularly to green light and the use of the monomethine dyes, 3,3-­diethyloxacyanine iodide, 3,3′-diethyl-4,5,4′,5′ dibenzothiacyanine iodide and 1,1′-diethyl 2,2-cyanine iodide among others is disclosed in this connection.
• these compounds are structurally similar to the compounds of formula (I) they were added solely to increase the spectral sensitivity of the silver halide material and there is no indication they have any activity as pepper fog inhibitors.
• spectral sensitisation beyond about 500 nm is undesirable since the coating is intended for safe handling under bright orange lighting conditions.
• Emulsions prepared in accordance with the invention show essentially no sensitivity at wavelengths beyond 540 nm, and a slightly enhanced sensitivity to the blue region.
• a white-light source they display a sensitivity that is only marginally less than that of a conventional green-sensitised lith emulsion, but their tolerance of amber safe-light is greatly improved.
• the emulsions show practically no pepper fog.
• the compounds of formula (I) may be present in a silver halide photographic emulsion or may be incorporated in layers other than the silver halide photographic emulsion layer, such as a protective layer, interlayers, a filter layer, etc. adjacent to the emulsion layer. It is, however, preferred for the compound of formula (I) to be incorporated in a surface latent image type silver halide photographic emulsion layer together with the hydrazine compound.
• the amount of the compound of formula (I) added is from 10 ⁇ 5 to 3 x 10 ⁇ 1, generally from 10 ⁇ 5 to 5 x 10 ⁇ 2 mole, per mole of silver contained in the silver halide photographic emulsion layer associated with the compound, but it is preferred to select the optimum content of the compound depending on the grain size of silver halide emulsion, the composition of the silver halide, the method and degree of chemical sensitisation employed and the type of hydrazine used. The method of testing for sensitisation is well known to one skilled in the art and can be easily accomplished.
• the compound may be added to an aqueous solution of a hydrophilic colloid as a solution in an organic solvent miscible with water, such as alcohols e.g. methanol, ethanol, etc, and ketones e.g. acetone, when the compound is oleophilic or as an aqueous solution when the compound is hydrophilic.
• an organic solvent miscible with water such as alcohols e.g. methanol, ethanol, etc, and ketones e.g. acetone
• the compound may be added at any time between the start of chemical ripening and the start of the coating process, but it is preferred to add the compound after the end of the chemical ripening of the silver halide emulsion. It is particularly preferred to add the compound to the coating composition of a silver halide photographic emulsion prepared for coating.
• the compound of formula (I) may posses one or more ring substituents of the type known in cyanine dyes.
• the compounds may be represented by the general formula: in which: each n independently represents 0, 1, 2, 3 or 4, each R3 and R4 may be the same or different and represent a substituent of the type known in cyanine dyes.
• substituents include halogen, carboxyl, hydroxy, cyano, alkyl, alkoxy, alkylthio and alkoxycarbonyl, or groups comprising combinations of the above substituents.
• the carbon atom chains of these substituents generally contain up to 10 carbon atoms, preferably 1 to 5 carbon atoms.
• R3 and/or R4 may also represent the atoms necessary to complete a carbocyclic or heterocyclic ring, which itself may bear substituents selected from the above list.
• At least one of R1 and R2 represents an organic group containing an acid function e.g. alkylsulphonate, alkylphosphate, alkyl carboxylate in which the alkyl groups generally contain 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms.
• the other of R1 and R2 may additionally represent a hydrogen atom or an alkyl group, generally of up to 10 carbon atoms, preferably 1 to 5 carbon atoms.
• the alkyl group may be substituted e.g. with the substituents listed above with respect to R3 and R4.
• Preferred compounds for use in the invention include those of the formula: in which R1 to R4 are defined above.
• the hydrazine compound present in the photographic element may comprise hydrazine or any hydrazine derivative capable of increasing speed and/or contrast of photographic silver halide emulsions.
• Such compounds are well known in the photographic art.
• suitable hydrazines will have the general formula: wherein: R11 is an organic radical, and R12, R13 and R14 each are hydrogen or an organic radical.
• Organic radicals represented by R11, R12, R13 and R14 include hydrocarbon groups, such as an alkyl group, an aryl group, an aralkyl group and an alicyclic group and such groups can be substituted with substituents such as alkoxy groups, carboxy groups, sulfonamido groups and halogen atoms.
• hydrazine derivatives are hydrazides, acyl hydrazines, semicarbazides, carbohydrazides and aminobiuret compounds.
• Hydrazine compounds suitable to be incorporated into the photographic element according to the present invention are disclosed in GB Patent Specification 598108 and in US Patent Specification 2419974; they include the water soluble alkyl, aryl and heterocyclic hydrazine compounds as well as the hydrazide, semicarbazide and aminobiuret compounds.
• a further class of hydrazine compounds, for use according to this invention incorporated in the photographic element, are the formylhydrazine compounds corresponding to the formula: R15-NHNH- -H wherein: R15 represents a substituted or unsubstituted aromatic group.
• aromatic groups represented by R15 include a phenyl group and a naphthyl group. Such aromatic groups may be substituted with one or more substituents which are not electron attracting, such as straight or branched-chain alkyl groups (e.g. methyl, ethyl, propyl, isopropyl, n-butyl, n-octyl, n-hexyl, tert.-octyl, n-decyl, n-dodecyl, etc.), aralkyl groups (e.g. benzyl, phenethyl, etc.), alkoxy groups (e.g.
• acylaminoaliphatic groups e.g. acetylamino, benzoylaminoetc.
• Such aromatic groups may also be substituted with a ureido group of formula: wherein: R16 and R17 (which may be same or different) each represents hydrogen, an aliphatic group (such as a straight or branched-chain alkyl group, a cycloalkyl group, a substituted cycloalkyl group, an alkenyl group and an alkynyl group), an aromatic group (such as a phenyl group and a napthyl group) or a heterocyclic group; R18 represents hydrogen or an aliphatic group (such as those listed above as described in US Patent 4323643.
• R16 and R17 each represents hydrogen, an aliphatic group (such as a straight or branched-chain alkyl group, a cycloalkyl group, a substituted cycloalkyl group, an alkenyl group and an alkynyl group), an aromatic group (such as a phenyl group and a napthyl group) or a hetero
• hydrazine compounds for use according to this invention incorporated in the photographic element, are those represented by the formula: R19-NHNH- -R20 wherein: R19 represents the same aromatic group of the formula above, and R20 represents an alkyl group having 1 to 3 carbon atoms, which may be a straight or branched-chain alkyl (e.g. methyl, ethyl, n-propyl and isopropyl) or a phenyl group.
• R19 represents the same aromatic group of the formula above
• R20 represents an alkyl group having 1 to 3 carbon atoms, which may be a straight or branched-chain alkyl (e.g. methyl, ethyl, n-propyl and isopropyl) or a phenyl group.
• the phenyl group may be substituted with one or more substituents which preferably are electron attracting groups, such as halogen atoms (chlorine, bromine, etc.), a cyano group, a trifluoromethyl group, a carboxy group or a sulfo group, etc.
• substituents such as halogen atoms (chlorine, bromine, etc.), a cyano group, a trifluoromethyl group, a carboxy group or a sulfo group, etc.
• hydrazine compounds for use according to this invention incorporated in the photographic element, are those corresponding to the formula: wherein: R21 represents hydrogen, an aliphatic group which may be substituted; Y represents a divalent linking group; m represents 0 or 1, W represents a divalent aromatic group (such as for example a phenylene group, a naphthylene group and the analogous substituted groups thereof); R22 represents a hydrogen atom, an aliphatic group which may be substituted and Z represents the non-metallic atoms necessary to form a 5- or 6-membered heterocyclic ring.
• R21 represents hydrogen, an aliphatic group which may be substituted
• Y represents a divalent linking group
• m represents 0 or 1
• W represents a divalent aromatic group (such as for example a phenylene group, a naphthylene group and the analogous substituted groups thereof)
• R22 represents a hydrogen atom, an aliphatic group which may be substituted
• Z represents
• ballasting groups such as the ballasting groups of incorporated colour couplers and other non-diffusing photographic emulsion addenda.
• Said ballasting groups contain at least 8 carbon atoms and can be selected from the relatively non-reactive aliphatic and aromatic groups such as alkyl, alkoxy, alkylphenyl, phenoxy, alkylphenoxy groups and the like.
• Such hydrazine compounds can be incorporated in the photographic element using various methods well-known in the photographic art, the most common being the method of dissolving the hydrazine derivatives in a high boiling solvent and dispersing the mixtures in the emulsion, as described for example in US Patent 2322027.
• R23 represents an aryl group
• the hydrazine compound is incorporated in the photographic element, for example in a silver halide emulsion layer or in a hydrophilic colloidal layer, preferably a hydrophilic colloidal layer adjacent to the emulsion layer in which the effects of the hydrazine compound are desired. It can, of course, be present in the photographic element distributed between the emulsion and the hydrophilic colloidal layers, such as one or more of a subbing layer, interlayers and protective layers.
• the hydrazines may be added to the silver halide photographic emulsion at any desired period from the initiation of chemical ripening to before coating, but it is preferred to add the compound after finishing chemical ripening. It is particularly preferred to add the compound to a coating composition prepared for coating.
• Hydrazines of formula (IV) may be incorporated as microcrystalline dispersions as disclosed in European Patent Application No. 89300866.4. In these cases, no water-immiscible solvent is used in the preparation of the gelatin dispersions.
• the hydrazine be incorporated in an amount of from 10 ⁇ 6 mol to 10 ⁇ 1 mol, and preferably from 10 ⁇ 5 mol to 5 x 10 ⁇ 2 mol per mol of silver halide but it is desirable to select the optimum amount of the compound according to the grain size of silver halide emulsion, the halogen composition, the manner and extent of chemical sensitization, and the kind of antifoggant compounds.
• the most appropriate compound and amount thereof for a particular use can be easily selected by general tests well known to persons skilled in the art.
• silver halide grains used for at least one silver halide emulsion layer in this invention be of substantially surface latent image type.
• the silver halide emulsion used in the invention may comprise any of silver chloride, silver chlorobromide, silver iodobromide, silver iodochlorobromide, etc., but preferably contains at least 60 mol% silver bromide.
• the iodide content is preferably not more than 10 mol% and more desirably is in the range of from 0.1 to 5 mol%.
• fine grains for example, 0.7 micron or less
• very fine grains of average diameter not larger than 0.5 micron are particularly preferable.
• a monodispersion is preferable.
• the term "monodispersion” as used herein means that, whether in weight or in number, at least 95% of grains are sized within ⁇ 40% of the mean grain size.
• the silver halide grains in the photographic emulsion may be regular crystals such as cubes or octahedra, or irregular crystals such as spheres or plates (tabular grains), or composites.
• Each of the silver halide grains may be made up of a uniform phase through its core and surface layer, or may be dissimilar in phase between the core and the surface. It is also possible to use two or more independently prepared silver halide emulsions as a mixture.
• a cadmium salt ruthenium, lead salt, thallium salt, rhodium salt or rhodium complex salt, iridium salt or iridium complex salt, or the like.
• Gelatin is preferably used as the binder or protective colloid for the photographic emulsion, but other hydrophilic colloids can also be employed, for example, gelatin derivatives, graft copolymers of gelatin to other high polymers, proteins such as albumin and casein, cellulose derivatives such as hydroxyethyl cellulose, carboxymethyl cellulose, cellulose sulphate esters, etc., sugar derivatives such as sodium alginate, starch derivatives, etc., and synthetic homo- or copolymers such as polyvinyl alcohol, partially acetalized polyvinyl alcohol, poly-N-vinylpyrrolidone, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyvinylimidazole and polyvinylpyrazole.
• hydrophilic colloids can also be employed, for example, gelatin derivatives, graft copolymers of gelatin to other high polymers, proteins such as albumin and casein, cellulose derivatives such as hydroxyethyl cellulose, carboxy
• the silver halide emulsion may be chemically sensitized.
• Known methods of chemical sensitization of silver halide emulsions include sulphur sensitization, reduction sensitization and noble metal sensitization, and the chemical sensitization may be effected by any or a combination of such methods.
• the usual method of the noble metal sensitization is gold sensitization and for this purpose a gold compound generally a complex salt of gold, is utilized.
• Complex salts of other noble metals such as platinum, palladium, rhodium, etc., may be additionally contained. Examples of this method are described in U.S. Patent 2448060 and British Patent 618061.
• Sulphur sensitizers include, in addition to sulphur compounds contained in gelatin, various sulphur compounds such as thiosulphates, thiourea compounds, thiazoles, and rhodanines.
• Reduction sensitizers include stannous salts, amines, formamidinesulphinic acid, silane or borane compounds and the like.
• the photographic elements may include a variety of compounds for the prevention of fog during production, storage or photographic processing or for the purpose of stablising its photographic qualities.
• the compounds referred to commonly as antifoggants or stabilizers for example various azole compounds such as benzothiazolium salts, nitroimidazoles, chlorobenzimidazoles, bromo-benzimidazoles, mercaptothiazoles, mercaptobenzothiazoles, mercaptotetrazoles, mercaptothiadiazoles, aminotriazoles, benzothiazoles, nitrobenzothiazoles, etc.; mercaptopyrimidines, thioketo compounds such as oxazolylthione, etc.; azaindenes such as triazaindene, teraazaindenes (particularly, 4-hydroxy-substituted­(1,3,3a,7)tetraazaindenes), pentaazaindenes, etc.
• azole compounds such
• benzenesulphinic acid benzenesulphonamide, etc.
• benzotriazoles e.g., 5 methylbenzo triazole
• nitroindazoles e.g., 5-nitroindazole
• these compounds may also be incorporated in the processing solution.
• the photographic elements may contain inorganic or organic hardening agents in the photographic emulsion layer or other hydrophilic colloid layer.
• chromium salts chrome alum, chromium acetate, etc.
• aldehydes formaldehyde, glyoxal, glutaraldehyde etc.
• N-methylol compounds dimethylolurea, methyloldimethylhydantoin, etc.
• dioxane derivatives (2,3-dihydroxydioxane, etc.
• active vinyl compounds (1,3,5 triacryloyl-hexahydro-s-triazines, 1,3,-vinyl-­sulphonyl-2-propanol, etc.
• active halogen compounds (2,4-dichloro-6-hydroxy-s-triazine, etc.
• mucohalogenic acids mucochloric acid, mucophenoxy-chloric acid, etc.
• a variety of surface active agents may be incorporated for various purposes such as improvement of coating properties antistatic properties slipping properties, emulsion dispersibility, anti-adhesion properties, and photographic properties (for example, development acceleration, increase in contrast, sensitization, etc.).
• nonionic surfactants are saponin, alkylene oxide derivatives e.g., polyethylene glycol, polyethylene glycol/polypropylene glycol condensate, polyethylene glycol alkyl ethers, polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalkylene glycol alkylamines or amides, silicone polyethylene oxide adducts), glycerol derivatives (e.g., alkenylsuccinic acid polyglyceride, alkylphenol polyglyceride), polyhydric alcohol-fatty acid esters, sugar alkyl esters, etc..
• alkylene oxide derivatives e.g., polyethylene glycol, polyethylene glycol/polypropylene glycol condensate, polyethylene glycol alkyl ethers, polyethylene glycol alkyl aryl ethers, polyethylene glycol esters, polyethylene glycol sorbitan esters, polyalky
• Anionic surfactants containing acid groups such as a carboxy group, a sulpho group, a phospho group, a sulphuric acid ester group, a phosphoric acid ester group, etc., for example alkylcarboxylates, alkylsulphonates, alkylbenzenesulphonates, alkylnaphthalenesulphonates, alkylsulphuric acid esters, alkylphosphoric acid esters N-acyl-N-alkyltaurines, sulphosuccinic acid esters, sulphoalkylpolyoxyethylene alkylphenyl ether, polyoxyethylene alkylphosphoric acid esters, etc.; amphoteric surfactants such as amino acids, aminoalkylsulphonic acids, aminoalkylsulphuric or phosphoric acid esters, alkylbetaines, amine oxides etc., may also be used.
• acid groups such as a carboxy group, a sul
• Cationic surfactants such as alkylamines, aliphatic or aromatic quaternary ammonium salts, heterocyclic quaternary ammonium salts such as pyridinium salts, imidazolium salts, etc., aliphatic or heterocyclic ring-containing phosphonium or sulphonium salts, etc. may be included.
• matting agents such as silica, magnesium oxide, polymethylmethacrylate, etc., may be incorporated for the purpose of preventing adhesion.
• the support of the photographic element may be made of cellulose triacetate, cellulose diacetate, nitrocellulose, polystyrene, polyethylene terephthalate or the like. However, the use of polyethylene terephthalate is particularly useful.
• Suitable developer compositions for use in the invention are any of those known in the art for development of hydrazine containing rapid access lith films and will generally have a pH in the range 9.5 to 12.5.
• the silver halide photographic elements provide a sufficient ultra-high contrast negative image using a developer containing at least 0.15 mol/litre of sulphite ion as a preservative, and having a pH value in the range of from 10.5 to 12.3 and particularly preferably in the range of from 11.0 to 12.3.
• the developing agents there is no particular limitation on the developing agents than can be employed in the method of this invention.
• dihydroxybenzenes e.g., hydroquinone
• 3-pyrazolidones e.g., 1-phenyl-3-­pyrazolidone, 4,4-dimethyl-1-phenyl-3-pyrazolidone
• aminophenols e.g., N-methyl-p-aminophenol, etc.
• dihydroxybenzenes e.g., hydroquinone
• 3-pyrazolidones e.g., 1-phenyl-3-­pyrazolidone, 4,4-dimethyl-1-phenyl-3-pyrazolidone
• aminophenols e.g., N-methyl-p-aminophenol
• the silver halide photographic element is especially suitable for processing with a developer containing a dihydroxybenzene compound as the developing agent and a 3-­pyrazolidone compound or an aminophenol compound as the auxiliary developing agent.
• the preferred concentrations of these compounds in the developer are from 0.05 to 0.5 mol/litre for the dihydroxybenzene, and 0.06 mol/litre or less for 3-pyrazolidone or aminophenol.
• amine compounds may be added to the developer to thereby increase the rate of development thereby reducing development time.
• the developer may be added to the developer other additives including pH buffers such as sulphites, carbonates, borates, and phosphates of alkali metals, development restrainers or antifoggants such as bromides, iodides and organic antifoggants (preferably nitroindazoles and benzotriazoles).
• pH buffers such as sulphites, carbonates, borates, and phosphates of alkali metals
• development restrainers or antifoggants such as bromides, iodides and organic antifoggants (preferably nitroindazoles and benzotriazoles).
• water softeners solubilizing agents or cosolvents, toners, development accelerators, surfactants (preferably aforesaid polyalkylene oxides), antifoams, hardeners, and silver stain inhibitors (e.g., 2-mercapto-­benzimidazolesulphonic acids) may also be incorporated in the developer.
• a solution of the conventional composition may be employed.
• Thiosulphates, thiocyanates, and those organic sulphur compounds which are generally known to be effective fixing agents can be used as fixing agents in the bath.
• the fixing bath may contain a water soluble salt of aluminium or the like as a hardener.
• a stop bath e.g. 1% acetic acid solution, may be employed.
• the processing temperature is generally selected within the range of from 18°C to 50°C.
• an automatic developing machine is desirably used, and a sufficient ultrahigh contrast negative image can be obtained even with a processing time, i.e., the time for entry of the photographic material into the machine to exit from the machine of from 90 to 120 seconds.
• a silver halide emulsion having halide mole percentage ratio of 68:30:2 of Br:Cl:I was prepared by a conventional double jet technique under constant pAg conditions.
• the resulting emulsion had a narrow grain size distribution with an average size of 0.25 microns.
• the emulsion was then coagulated and washed being reconstituted to 95g gelatin per mole of silver.
• the emulsion was chemically sensitised with sodium thiosulphate in the conventional fashion. Additions were also made before coating onto subbed polyester base, a monomethine benzothiazole as reported in the following Table, and then an anionic wetting agent (Hostapur SAS93) (10ml of 10% solution), polyoxyethylene cetyl ether (surfactant) (150ml of 1% solution), a contrast promoting agent (benzhydrol) (30 ml of 5% solution in methanol) and a hydrazine derivative (3g):
• the order of addition was not critical but preferably the monomethine benzothiazole was added first.
• the emulsion was coated at a silver coating weight of 3.5g per square metre.
• a gelatin topcoat comprising 50g gelatin per 1000g water, wetting agent, matting agent (silica), and a hardener (2-hydroxy-4,6-dichloro-1,3,5-triazine).
• Dot quality was assessed by making an exposure using a tungsten filament lamp through a Kodak "Ultratec" contact halftone screen held in contact with the film sample by a vacuum frame, and processing as before.

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