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

• the present invention relates to a process for inhibiting the aerial oxidation of a tanning developer, and more particularly to a process whereby this oxidation is inhibited by the use of a stable anti-oxidizing agent which does not compete with the tanning developing substance.
• polyhydroxybenzenes especially pyrocatechol and pyrogallol, both in alkaline medium
• the drawbacks of such developers are their instability and their quite rapid darkening and uselessness by aerial oxidation.
• Sodium sulphite generally known as a very fiective agent against aerial oxidation of developers cannot be used or at least not in the necessary amount in a tanning developer since the formed oxidation products of the developing substance react with the sodium sulphite and not with the gelatin, so that the latter is not hardened anymore on the exposed areas, with the consequence that no relief image can be obtained anymore; in most cases, the tanning developers are prepared just before use and discarded after use.
• vitamin C vitamin C
• tanning developers U.S.P. 2,415,666
• ascorbic acid vitamin C
• ascorbic acid is unstable in alkaline medium which results in a strong decrease of the anti-oxidizing action.
• the relief image on removing the non-developed unhardened gelatin, is insufliciently hardened and is either completely or partially washed away by the warm water. This occurs in particular when relatively large quantities of ascorbic acidwhich owing to the instability of ascorbic acid in alkaline medium are necessary to keep useful the tanning developer for a sufliciently long periodare added to the developer,
• .It is an object of the present invention to provide a photographic tanning developerwhich is stable to aerial tilling the water under reduced pressure.
• a further object is to provide a novel antioxidizing agent which does not compete with the tanning developer substance used.
• a silver halide tanning developer solution comprising an alkaline solution of a polyhydroxybenzene, of a water soluble salt of an ascorbic acid borate. It was stated, indeed, that the as.- corbic acid borates contrary to the free ascorbic acid, are very stable in alkaline medium where they act as their corresponding salts, and moreover that theydo not compete with the tanning developer substance used.
• Ascorbic acid borate is prepared by esterifying ascorbic acid with boric acid. When the esterification is carried out in the presence of a base, salts of ascorbic acid borate are obtained. In this way, potassium ascorbic acid borate can be obtained by heating'to 70 C. 2 mol eq. of ascorbic acid with 1 mol eq. of boric acid and 1 mol eq.
• hydroxides of alkali, metals such as sodium hydroxide, or hydroxides of alkalineearth'metals, such as barium hydroxide, or still other hydroxides, such as ammonium hydroxide, the corresponding salts of ascorbic acid borate can be prepared.
• a further great advantage of the ascorbic acid borates in respect of ascorbic acid is. the very strongly reduced competition with the present tanning developer substance duringdevelopment.
• a photographic paper provided with a light-sensitive silver halide emulsion is exposed to an image and divided into three strips. Each strip is immersed for one minute at 20 C. in developers C/D, and E resp. On washing in warm Water, the developed areas obtained with the rel nted Jan. 10, 1,9 1
• the developers which stability to aerial oxidation is increased by the application of the process according to the present invention can possess besides the tanning developer substance and the ascorbic acid borate, still other usual bath ingredients such as for instance wetting agents and sequestering compounds.
• Example I A contrasty light-sensitive silver halide emulsion on a paper support is exposed to an image and developed for 1 minute at 20 C. in the following bath:
• Example 2 A contrasty light-sensitive silver halide emulsion on a paper support is exposed to an image and developed for 1 minute at 20 C. in the following bath:
• Example 3 A contrasty light-sensitive silver halide emulsion on a 4 paper support is exposed to an image and developed for 1 minute at 20 C. in the following bath:
• Example 4 A contrasty light-sensitive silver halide emulsion on a paper support is exposed to an image and developed for 1 minute at 20 C. in the following bath:
• a photographic tanning developer solution having reduced tendency to aerial oxidation and capable of forming relief images upon development of an exposed silver halide emulsion comprising an alkaline solution of a polyhydroxybenzene selected from the group consisting of pyrogallol and pyrocatechol and a water-soluble salt of a boron ascorbic acid compound which is the reaction product of boric acid and ascorbic acid.
• a developer as defined in claim 1 wherein the salt is an alkali-metal salt.
• a developer as defined in claim 1 wherein the salt is an alkali-earth metal salt.
• a developer as defined in claim 1 wherein the salt is an ammonium salt.

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=19750970

Family Applications (1)

Country Status (6)

Cited By (2)

Citations (2)

• 1957
  • 1957-09-05 NL NL220541A patent/NL96063C/xx active
• 1958
  • 1958-09-02 US US758576A patent/US2967772A/en not_active Expired - Lifetime
  • 1958-09-04 FR FR1202502D patent/FR1202502A/fr not_active Expired
  • 1958-09-04 DE DEG25246A patent/DE1060715B/de active Pending
  • 1958-09-04 GB GB28424/58A patent/GB862615A/en not_active Expired
  • 1958-09-04 BE BE570926A patent/BE570926A/xx unknown

Patent Citations (2)

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