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
  • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
  • G03C5/26—Processes using silver-salt-containing photosensitive materials or agents therefor
  • G03C5/29—Development processes or agents therefor
  • G03C5/315—Tanning development

Definitions

• an exposed gelatino silver halide emulsion layer is tanning developed by means of an alkaline developing solution containing pyrogallol, pyrocatechol or hydroquinone. It is known from the U.S. patent specification 2,967,772 that such a developing solution is quite easily oxidized by air, thus becoming strongly colored and difiicult to keep.
• tanning developers are liable to aerial oxidation especially in alkaline medium.
• the exposed material is developed in an alkaline activating bath, after dipping in a neutral or slightly acid solution of the tanning developing substance.
• This developing method has the advantage that rapid exhaustion of the developing bath by aerial oxidation is avoided said method being, however, cu-mbrous.
• this tanning developed materials is used for producing a gelatin relief, the parts of the emulsion corresponding to the stained areas which are exposed too little and not completely hardened, are partially removed when washing away the unhardened parts of the emulsion.
• a tanning developed emulsion layer to another support e.g. paper by pressing the layer against said support, an irregular transfer is realized.
• hydroquinone as tanning developer compared to pyrocatechol and pyrogallol is the less selective tanning action. This occurs especially when incorporating the hydroquinone into the light-sensitive emulsion layer. According to P. Glafkides, Chimie Photographique, 2nd ed., p. 534, only pyrogallol gives a local hardening strictly corresponding to the exposed areas. Although hydroquinone shows certain advantages over pyrogallol and pyrocatechol as mentioned above, the unsharp hardening was the principal reason why it was not used as tanning developer to a larger scale. A localized hardening, strictly corresponding to the exposed areas, is especially important in the reproduction of documents and drawings and in screen exposure.
• the characters and lines appearing in texts and drawings possess generally a line-width smaller than 1 mm.
• the narrow undeveloped areas on the light-sensitive material corresponding to these lines are hardened together with the developed areas, especially when hydroquinone is used as tanning developer, so that they can neither be washed away with warm water nor be transferred to another support by pressing against said support. It is assumed that the hardening in said narrow undeveloped areas arises by the oxidized developer (quinone compound) it is formed in the exposed areas during the reduction of the silver halide, diffusing into said narrow undeveloped areas.
• the hardening on the developed areas is very intense when using hydroquinone, the hardening on the undeveloped areas can be counteracted to a certain extent by incorporating into the emulsion or the bath a softening agent such as urea without decreasing considerably the hardening on the developed areas. It is not possible however, by such use of urea during tanning development to obtain a selectively hardened image pattern within a practically useful range of exposure.
• the softening effect of urea on gelatin is described in the U.S. patent specification 2,404,774.
• sulfite ions from metabisulfites, sulfites or bisulfite restrain the tanning development. It is presumed that the oxidized developer reacts with sulfite and that as a result thereof the hardening by the reaction of the gelatin with the oxidized developing substance is inhibited.
• P. Glafkides describes in Chimie Photographique, 2nd ed., page 534, that the hardening action is only complete in the presence of very little sulfite.
• sulfite ions are incorporated into alkaline developing baths and light-sensitive gelatino emulsion layers in order to prevent aerial oxidation of the developer.
• aromatic hydroxy compounds which according to the present invention in combination with hydroquinone increase the selectivity of the hardening are mentioned: u-naphthol, ,B-naphthol, polyhydroxybenzene compounds having at least two hydroxy groups in meta position with respect to each other such as resorcinol and phloroglucinol. The latter, however, is preferred.
• aromatic hydroxy compounds may be added to the emulsion and/or developing bath with or without hydroquinone. They are, however, preferably incorporated into the gelatino silver halide emulsion layer together With some hydroquinone and bisulfite as stabilizer against aerial oxidation.
• Primary amino compounds capable of reacting with quinone are all primary aliphatic and aromatic monoor polyamino compounds.
• the primary amino compounds used according to the invention must possess no or almost no developing activity and should preferably be well soluble in the alkaline developing or activating bath.
• unsubstituted as well as substituted primary amines may be used.
• the primary amines are preferably substituted by water-solubilizing groups e.g. hydroxy groups, groups splitting off hydrogen ions such as carboxyl groups, sulfonic acid groups, phosphoric acid groups or the salts of these groups.
• unsubstituted primary amines examples include monomethylamine and monoethylamine.
• Unsubstituted aromatic primary amines are preferably not used because of their poisonness.
• the unsubstituted primary amines are preferably added to the bath and not to the composition of the light-sensitive gelatino silver halide emulsion layer.
• substituted primary amines compounds are: amino carboxylic acids such as amino acetic acid and amino succinic acid, amino sulfonic acids such as amino ethane sulfonic acid and 2,2-disulfo-4,4'diaminodiphenyl and aliphatic hydroxyamino compounds such as ethanolamine.
• the primary amino compounds substituted with acid groups or acid groups in salt form are very suited for use in the gelatino silver halide emulsion layer as well as for use in developing or activating bath.
• a compound splitting off bisulfite ions such as potassium metabisulfite (K S O is preferably incorporated therein.
• K S O potassium metabisulfite
• the amount of incorporated compound splitting 0ft bisulfite ions is preferably at most 0.5 mole per mole of hydroquinone in order to still obtain an appropriate hardening.
• Examples of developing activators which may be added to the emulsion are the polyoxyalkylene derivatives described in the British patent specification 920,637 and in the Belgian patent specification 609,497 and 609,944.
• the maximum amount of hardening restraining compounds used according to the present invention for still obtaining a sufiicient hardening is not the same for each combination. It was stated that the amount of hardening restraining compounds used in the present invention is preferably not higher than 30 to 35 mol percent based on the amount of hydroquinone available for development. If phloroglucinol is used, the amount of phlorogl-ucinol inc-orporated into the gelatino silver halide emulsion layer is preferably between 0.5 and 2.5 g. per g. of hydroquinone.
• Tanning development according to the present invention may be carried out according to various methods, according to whether the compound for more selective hardening is present in the light-sensitive layer, in an alkaline developing bath or in an alkaline activating bath and the hydroquinone is incorporated in the developing bath or in the light-sensitive emulsion layer.
• the developing bath containing hydroquinone as well as the activating bath may contain the usual ingredients such as developing activators and antifogging agents in addition to the required amount of alkali for instance sodium carbonate.
• Suitable antifogging agents are: potassium bromide, benzotriazole and 1-phenyl5-mercaptotetrazole. These compounds, however, are not essential for the more selective tanning development according to the present invention.
• a compound capable of splitting off sulfite ions is preferably added to the bath in order to avoid aerial oxidation of the hydroquinone.
• Said compound is added in an amount of at most 0.4 mole per mole of .hydroquinone. A larger amount is undesirable since the tanning development is then too much restrained or even completely inhibited.
• a softening agent e.g. urea is incorporated in the developing bath or in the activating bath.
• the tanning development according to the present invention gives favorable results in the preparation of etching resists for use in photomechanical processes.
• a gelatin emulsion layer tanning developed according to the present invention is transformed by dissolving the weak emulsion parts (the so-called Washing away) in an etching resist.
• the manufacture of etching resists starting from an exposed gelatino silver halide emulsion layer is described e.g. in the Belgian patent specification 627,076.
• the tanning development according to the present invention gives favorable results especially in the manufacture of hectographic masters (cf. the Belgian patent specifications 596,508 and 600,508 and the British patent specification 804,076). According to these processes the weak gelatin parts of the tanning developed emulsion layer have to be easily and selectively transferred to another support such as paper by pressing said layer against said support.
• the present invention presents an important progress especially in the manufacture of masters for spirit duplicating as described in the Belgian patent specifications 596,508 and 600,508 since using the compounds increasing the selectivity of the hardening according to the present invention in combination with a light-sensitive material of good stability and a stable activating bath, a sharp reproduction of characters or lines having a line width of 1 mm. is obtained.
• a hectographic master is produced as follows:
• a negative image e.g. a microfilm image
• the tanning developed emulsion layer is pressed against a hectographic carbon paper and then both sheets stripped apart so that the weak gelatin covers the dyestutf layer of the carbon paper on the areas corresponding to the unexposed areas of the emulsion layer.
• the carbon paper is used as master sheet on a usual spirit duplicator for making legible positive prints.
• a master sheet for a spirit duplicator is produced by the following steps:
• a negative print of an original is made on the gelatino silver halide emulsion layer by reflectographic exposure through the back of the support;
• the unh-ardened gelatin has been transferred to the art printing paper and has pulled out dyestuff from the dyestutf layer.
• the art printing paper which after being separated from the carbon paper carries a laterally reversed image of the original composed of gelatin which is covered with dyestufi is used as hectographic master in a spirit duplicator.
• tanning development In order to show the selectivity of the tanning development according to the present invention, a series of the same image-wise exposed light-sensitive materials was tanning developed in different developing compositions which in addition to hydroquinone contain a known hardening restraining substance such as potassium sulfite or a hardening restraining compound used according to the present invention.
• a known hardening restraining substance such as potassium sulfite or a hardening restraining compound used according to the present invention.
• the light-sensitive materials used for these developing tests were composed of a paper support of 135 g./sq. m. coated with a contrasty light-sensitive gelatino silver halide emulsion comprising per kg. of emulsion 64 g. of gelatin, 40 g. of silver chloride and 50 g. of urea.
• the light-sensitive materials were reflectographically exposed through a step-wedge having a constant of 0.05 to a typographical text showing characters having a linewidth of 0.5 mm.
• the developing solution to which the hardening restraining compounds listed in the table below are added in turn, has the following composition:
• the exposed material is developed at 30 C. for 20 sec.
• gelatino silver halide emulsion according to the present invention and ready for coating comprises in addition to the required amount of water, antifogging agents, sensitizers and developing activators:
• Both emulsion layers are analogously reflectographicall exposed to a text the characters of which show a line-Width of at most 1 mm. Development occurs in the alkaline activating hath given below and containing each time another combination of hardening restraining compounds.
• the materials are developed at 30 C. for 20 sec.
• combination 4 is not preferred.
• the adhesive power of the emulsion parts corresponding with the unexposed areas decreases rapidly when developing many negatives.
• the activating bath used in combination 6 is much more stable against exhaustion.
• the dry emulsion :layer is reflectographioally exposed to a typographical text and developed for 20* sec. at 30 C. in an activating solution of the following composition:
• the undeveloped emulsion areas corresponding to the characters of the original can easily and selectively be washed away with water of about 50 C.
• Example 2 A paper support of 135 g./sq. m. is coated with a thin layer from the following composition:
• the emulsion layer is refiect-ograp-hically exposed to a typographical text and developed for 2.0 sec. at 30 C. in an activating solution of the following composition:
• the undeveloped emulsion areas corresponding to the characters of the original can easily and selectively be washed away with water of about 50 C.
• Example 3 Example 1 is repeated with the exception that in the activating solution 10 g. of monoethanolamine are replaced by 2 g. of resorcinol.
• Example 4 To 1 kg. of a gelatino silver halide emulsion comprising 75 g. of gelatin and 45 g. of silver chloride per kg. are successively added a solution of 10 g. of hydroquino-ne and l g. of phloroglucinol in 50 cos. of ethanol, a solution of 8 g. of potassium metabisulfite in 50 cos. of distilled water and 50' g. of urea.
• the emulsion is homogeneously mixed and coated onto a paper support provided with a layer of colloidal silica as described in Example 2.
• the exposed material is developed for 20 sec. at 30 C. in a solution of the following composition:
• the developed negative is immersed in water of about 50 C. so that the unhardened areas can easily be removed by rubbing with a rubber scraper.
• Example 5 A tanning-developed negative obtained according to the method described in Example 4 is not treated with warm water but pressed with the emulsion layer against the dyestulf layer of a commercially available hectographic carbon p per, whereupon the materials pressed together are passed between two rubber pressure rollers. After 20 to 40 see. the two materials are stripped apart and the unhardened gelatin emulsion areas of the negative adhere to the dyestufi layer of the hectographic carbon paper.
• the surface of the hectographic carbon paper should not be perfectly hydrophobic and hence before use it is occasionally degreased with naphtha and afterwards dried.
• the hectographic carbon paper covered with the transferred weak gelatin is laid down with its back onto a smooth plate and pressed against a sheet of a glossy china clay-coated paper (art printing paper) by means of a rubber roller. After 2 min. of drying, the art printing paper is stripped apart from the carbon paper. By this treatment the gelatin adhering to the art printing paper pulls out a part of the dyestull from the dyestufr" layer of the carbon paper and so forms on the art printing paper a laterally reversed gelatin image covered with dyestuflf.
• This are printing paper can be used as hectographic master in a spirit duplicator. More than legible prints can be obtained.
• Example 6 Example 4 is repeated with the exception that in the emulsion 1 g. of phloroglucinol is replaced by 3 g. of a-naphthol. The results are identical to those obtained in Example 4.
• Example 7 The light-sensitive material of Example 6 is used for preparing a hectographic master as described in Example 5. Clear prints are obtained with said master.
• Example 8 Example 4 is repeated with the exception that in the emulsion 1 g. of phloroglucinol is replaced by 2 g. of resorcinol. The results are identical to those obtaine in Example 4.
• Example 9 l The light-sensitive material of Example 8 is used for preparing a hectographic master as described in Example 5. Prints with a good definition are obtained with said master.
• Example 10 A light-sensitive material as described in Example 4 is developed in a solution of the following compositions:
• the developed material is further treated as in Example 5.
• Example 11 A paper support of g./sq. m. is coated with a thin silica as described in Example 2.
• a silver halide emulsion is also prepared as in Example 2 with the exception, however, that moreover 5 g. of an aqueous solution of amino-acetic acid are added per kg. of emulsion.
• the emulsion layer is reflectographically exposed to a typographical text and developed for 20 sec. at 30 C. in an activating solution of the following composition:
• a process for producing a relief image in an imagewise exposed light-sensitive gelatino silver halide emulsion layer comprising subjecting said layer to tanning development with hydroquinone to form hardened and non-hardened areas, said tanning development being carried out in the presence of a harden ing inhibiting compound substantially free of silver halide developing activity and selected from the group consisting of (a) an aromatic hydroxy compound of the group consisting of a naphthol and a polyhydroxy benzene having at least two hydroxyl groups in meta position relative to one another, and
• said hardening inhibiting compound is an aromatic hydroxy compound incorporated in the light-sensitive gelatino silver halide emulsion layer.
• Light-sensitive photographic material for image wise exposure with light and development in an aqueous alkaline liquid comprising at least one silver halide emulsion layer and having incorporated therein:
• Hydroquinone in amount generally sufiicient to cause tanning development in the exposed areas of said layer in the presence of said aqueous alkaline liquid;
• a tanning inhibiting agent in an amount up to about 35 mole percent of said hydroquinone and generally sufficient to inhibit tanning development in the unexposed areas of said layer, said agent being free of developing activity and selected from the group consisting of;

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Non-Silver Salt Photosensitive Materials And Non-Silver Salt Photography (AREA)
• Photosensitive Polymer And Photoresist Processing (AREA)

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Cited By (3)

Citations (9)

• 0
  • BE BE631556D patent/BE631556A/xx unknown
  • NL NL277701D patent/NL277701A/xx unknown
• 1963
  • 1963-04-24 AT AT332963A patent/AT252031B/de active
  • 1963-04-24 CH CH512163A patent/CH446066A/de unknown
  • 1963-04-24 US US275203A patent/US3293035A/en not_active Expired - Lifetime
  • 1963-04-25 DE DE19631447676 patent/DE1447676A1/de active Pending
  • 1963-04-26 GB GB16618/63A patent/GB1049191A/en not_active Expired
  • 1963-04-26 GB GB14550/66A patent/GB1049192A/en not_active Expired

Patent Citations (9)

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