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
  • G03C7/00—Multicolour photographic processes or agents therefor; Regeneration of such processing agents; Photosensitive materials for multicolour processes
  • G03C7/28—Silver dye bleach processes; Materials therefor; Preparing or processing such materials

Definitions

• ABSTRACT OF THE DISCLOSURE A process for the production of colored photographic images by the silver dyestuff bleaching process, wherein bleaching is carried out in a dyestuff bleaching bath containing a pyrazine as bleaching catalyst or a pyrazine is added to a bath preceding the dyestuff bleaching bath or wherein photographic material is used that contains at least one layer containing a pyrazine as bleaching catalyst.
• the present invention relates to dyestuff bleaching catalysts for the silver dyestuff bleaching process.
• the production of colored photographic images by the silver dyestuff bleaching process is based on the principle that organic dyestuffs, especially azo dyestuffs, are destroyed by metallic silver in suitable baths.
• these baths contain a mineral acid, for example, hydrochloric acid, or a strong organic carboxylic acid, potassium bromide and a compound capable of forming silver complexes, for example, thiourea.
• a mineral acid for example, hydrochloric acid
• a strong organic carboxylic acid, potassium bromide a compound capable of forming silver complexes, for example, thiourea.
• 4 silver atoms reduce one azo group with formation of colorless amines.
• azo dyestuffs differ greatly from one another in respect of their behaviour in this reduction process, the differences being mainly in the time required to bring about reduction to a colorless substance.
• the silver dyestuff bleaching process is generally not carried out to its conclusion with utilization of the total amount of metallic silver present, but is tenninated after a certain period after only a proportion of the said silver has been consumed.
• bleaching continues at those areas where metallic silver is still present, which means that there may be a paucity of halftones, particularly at areas of low color density.
• a catalyst is required in the bleaching of some azo dyestuffs in order to equal out a large extent the bleaching times for the different dyestuffs and, Where necessary to permit bleaching to a pure white.
• Compounds that have been proposed as bleaching catalysts, and some of which have been used successfully are, for example, 2:3 dimethylquinoxaline, 2:3 diaminophenazine, 2-hydroxy-3-aminophenazine and anthraquinone sulphonic acid.
• the catalysts are added to the silver dyestuff bleaching bath in the usual manner, or are incorporated in the photographic color layer. It is also known to add the catalysts to a bath preceding the silver dyestuff bleaching bath.
• catalysts and methods of using them available. Nevertheless, the use of catalysts is frequently beset with difficulties. In particular, it is difficult to catalyse the bleaching process in a manner such that the different dyestuffs present in multilayer material are properly attuned to one another as regards bleaching. For example, a particular catalyst can shorten the bleaching time of the yellow and cyan dyestuffs but have no influence on the bleaching time of the magenta dyestuff. Conversely, the magenta dyestuff can respond well to a catalyst and the yellow and cyan dyestuffs remain unaffected.
• a further disadvantage associated with the bleaching caralysts known hitherto is that the compounds that are effective in low concentrations of about 1 to 10 milligrams per liter as, for example, 2:3 diaminophenazine and 2- hydroxy-3-aminophenazine, have a very pronounced color of their own. This can result in undesirable coloration of the gelatine or support.
• the known uncolored catalysts for example, 2:3-dimethylquinoxaline, have a much weaker action and thus have to to used in larger amounts.
• disazo dyestuffs especially cyan disazo or azoxyazo dyestuffs
• the well-known symmetrical disazo dyestuff obtained from tetrazotized 3:3- dirnethoxy 4:4 diaminodiphenyl and 1 amino-S-hydroxynaphthalene-Z:4-disulphonic acid
• bleaching with the known catalysts proceeds in a manner such that only the first azo group is split up and a violet monoazo dyestuff is left in the layers. It is therefore desirable to have catalysts that catalyse the splitting'of the monoazo dyestuff that is produced; the said dyestuff is particularly noticeable and undesirable at the white areas of the image.
• the present invention is based on the observation that specially good results are obtained when pyrazines are used as bleaching catalysts in the silver dyestuff bleaching process.
• the present invention therefore provides a process for the production of colored photographic images by the silver dyestuff bleaching process, wherein bleaching is carried out in a dyestuff bleaching bath containing a pyrazine as bleaching catalyst or a pyrazine is added to a bath preceding the dyestuff bleaching bath or wherein photographic material is used that contains at least one layer containing a pyrazine as bleaching catalyst.
• the pyrazines possess surprisingly advantageous properties compared with the known dyestuff bleaching catalysts.
• they are colorless and are effective when used in very low concentrations, and they also catalyse the second reaction step in the case of many known cyan dyestuffs; in other Words, they ensure bleaching of the monoazo dyestuff to colorless cleavage products.
• pyrazines refers solely to compounds containing at least one ring of the formula which is not condensed with other rings, which ring may also be depicted in a simplified manner as follows:
• the pyrazine ring may carry substituents, for example, this catalyst is capable of promoting the complete bleachcarboxylic acid groups or alkyl groups, for example, ethyl ing of all dyestuffs. When used in higher concentrations groups or especially methyl groups. For example, catalysts it also acts on layers that do not contain silver and is can be used that correspond to the formula thus the cause of so-called bleach-coupling. (3) N 5 The last-mentioned property is much less pronounced in the case of the substitution products of pyrazine, and EFF -Rz the latter have therefore been found to be especially ⁇ N valuable because of their specific action on certain dyestuffs.
• the photographlc mateflal d pyrazines of the kind d fi d can be derived f example, tains three colored layers on a support of cellulose acetate from 2-amino-3:6-dimethylpyrazine on the one hand and film, and 1S bill p as fOH'OWSI from a monocarboxylic add f example, benzoic acid,
• the said pyrazines can COH1 I H (?CH3 Ht) be added to the photographic color layer, to an intermediate layer, to the dyestufi" bleaching bath or to a bath preceding the dyestuff bleaching bath, for example, to the developer, a hardening bath, a stop bath or a special bath H035 "303E l) following the fixing bath. Furthermore, it can also be ad- 40 vantageous to use the pyrazines in conjunction with dye- Hots stuff bleaching catalysts having a different constitution, Second layer: A gelatine intermediate layer. for example, with quinoxalines or phenazines. For ex- Third layer: A green-sensitized silver bromide emulsion ample, the pyrazines can be used as catalysts in combinacontaining a magenta dyestuff of the formula.
• a gelatine intermediate layer aminohydroxyphenazine.
• a layer containing a yellow filter dye- Unsubstituted pyrazine is a colorless compound which stuff or colloidal silver acting as yellow filter.
• halogenated triazine zine per liter of bleaching bath comprising to parts compound, for example, with 2:4-dichloro-6-phenylof hydrochloric acid of 30% strength, 100 to parts amino-1:3:5-triazine-3-sulfonic acid.
• the material is washed in water for a short time, and then bleached in a silver dyestuff bleaching bath containing, per liter of water, 30 grams of thiourea, grams of potassium bromide, 70 ml. of hydrochloric acid of 30% strength and 3 ml. of a 1% solution of 2:5-dimethylpyrazine in water.
• the bleaching time is 8 to 15 minutes.
• the material is given a short wash with water and then the residual metallic silver is converted into silver halide in the usual manner in a bath containing copper sulphate, hydrochloric acid and potassium bromide.
• the material is then washed with water, fixed with a 10% solution of ammonium thiosulfate and again washed.
• the aminodimethylquinoxaline in the developer can be replaced 'by 2:5-dimethylpyrazine in amounts of 0.005 to 0.01 gram per liter of developer or by 2-amino-3-hydroxyphenazine hydrochloride.
• casting material contains 160 to 230 grams of gelatine (depending on the degree of viscosity required) and also 145 to 500 ml. of an aqueous or alkaline solution of 1.5 grams of the catalyst, for example, pyrazine-2:3-dicarboxylic acid or 2-benzoylamino-3z6-dimethylpyrazine.
• the catalyst for example, pyrazine-2:3-dicarboxylic acid or 2-benzoylamino-3z6-dimethylpyrazine.
• the incorporated catalysts diffuse into the dyestutf layer and promote uni form bleaching of the dyestuffs.
• EXAMPLE 3 Material having the composition indicated in Example 1 is treated in the manner described in Example 1. However, instead of 3 ml. of a 1% aqueous solution of dimethylpyrazine, 10 to ml. of a 0.2% solution of one of the following pyrazine compounds in methanol are added to the bleaching bath:
• the improvement which comprises carrying out the silver dyestuif bleaching operation in the presence of the pyrazine of the formula HaC N .as a dyestuif bleaching catalyst.
• the improvement which comprises carrying out the silver dyestulr' bleaching operation in the presence of the pyrazine of the formula as a dyestuff bleaching catalyst.
• the improvement which comprises carrying out the silver dyestutf bleaching operation in the presence of the pyrazine of the formula N Wl-c 0 on COO1I as a dyestuif bleaching catalyst.
• the improvement which comprises canying out the silver dyestuff bleaching operation in the presence of the pyrazine of the formula as a dyestuif bleaching catalyst.
• a silver dyestuff bleaching bath containing in Vitus thiourea, potassium bromide, a strong acid and a pyrazine of the formula in which R and R each represents a member selected from the group consisting of a hydrogen atom, a methyl group and a carboxylic acid group as a dyestufi bleaching catalyst.

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• General Physics & Mathematics (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)

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Citations (2)

• 0
  • GB GB1051970D patent/GB1051970A/en active Active
• 1964
  • 1964-03-20 CH CH361864A patent/CH438936A/de unknown
• 1965
  • 1965-03-10 ES ES0310746A patent/ES310746A1/es not_active Expired
  • 1965-03-16 US US440303A patent/US3394004A/en not_active Expired - Lifetime
  • 1965-03-19 BE BE661358A patent/BE661358A/xx unknown
  • 1965-03-19 NL NL6503517A patent/NL6503517A/xx unknown
  • 1965-03-19 DE DEP1269A patent/DE1269483B/de active Pending
  • 1965-03-19 AT AT251865A patent/AT257358B/de active

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