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
  • G03C5/38—Fixing; Developing-fixing; Hardening-fixing
  • G03C5/39—Stabilising, i.e. fixing without washing out
• • 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
• • 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
  • G03C5/40—Chemically transforming developed images
  • G03C5/44—Bleaching; Bleach-fixing

Definitions

• the present invention relates to a method of processing holo­graphically exposed silver halide sensitised holographic material.
• a silver image is formed and the developed silver is bleached leaving in the processed hologram the unexposed silver halide in the gelatin binder.
• the presence of the unexposed silver halide helps to form brighter holograms than those holograms wherein the unexposed silver halide has been fixed out during the processing.
• holograms are often stored in daylight and very commonly are exposed to a strong light source for long periods of time to reconstruct the image.
• holograms which contain residual silver halide are so treated after a period of time the residual silver halide tends to print out silver. Whilst this does not affect directly the reconstruction of the hologram it is unsightly and tends to lessen the brightness of the hologram on reconstruction.
• a method of processing holographically exposed silver halide sensitised holographic material which comprises developing the material in a photographic developing solution, and bleaching the developed silver, the method being characterised in that it comprises treating the material after the bleaching step with an aqueous solution of at least one compound which has a cathodic reduction potential of more than - 1 volt versus a standard calomel electrode as determined by the cyclic voltammetric method hereinafter defined.
• the material is treated with an aqueous solution of a compound which has a cathodic reduction potential of more than 0.4 volts versus a standard calomel electrode as determined by the cyclic voltammetric method.
• the strength of the aqueous solution used to treat the material after the bleaching step is between 1 to 3 g of the compound per litre.
• the length of treatment is also important. If for example the strength of the aqueous solution is 2g per litre then a suitable treatment time is two minutes.
• Cyclic voltammetry is a technique used in electrochemical investigations such as the determination of redox potentials.
• the parameters of the cyclic voltammetry technique employed as these affect the apparant cathodic reduction potential. These parameters are the solvent used for the compound being tested, the supporting electrolyte used if the compound being tested has low electroconductivity, the nature of the three electrodes employed, viz, the standard electrode, the working electrode and the auxilary electrode. Further the sweep range of potential and the sweep rate in minivolts per second should be defined. Two other parameters which should be noted are the concentration of the compound in the solvent and the temperature at which the determination was carried out.
• a B.B.C. microcomputer was used to provide the required ramped voltage.
• the voltammograms shown on the computer screen were dumped onto a Epson plotter and the cathodic reduction potential of each compound was determined from the voltammogram.
• Particularly useful classes of compounds which have a cathodic reduction potential of more than - 1 volt versus a standard calomel electrode are compounds of the general formula and compounds of the general formula wherein each of R1 and R2 are optionally substituted alkyl, cycloalkyl, aralkyl or aryl, R3 and R4 are each hydrogen, halogen, or optionally substituted alkyl or alkoxy containing 1 to 4 carbon atoms, R5 and R6 are each hydrogen or optionally substituted alkyl containing 1 to 4 carbon atoms, L is a direct link, an unsaturated link or a direct link and an unsaturated link, X ⁇ is an anion, n is 0, 1 or 2, m is 2, 3 or 4.
• the prefered compounds of formula (1) are those wherein R3 and R4 are each hydrogen and R1 and R2 are each optionally substituted alkyl having 1 to 4 carbon atoms.
• a specially preferred aralkyl group is benzyl.
• the preferred compounds of formula (2) are those wherein each of R3, R4, R5 and R6 are hydrogen atoms.
• L is a direct link or is a direct link and an unsaturated link and m is 2.
• the compounds of both formula (1) and (2) all have a cathodic reduction potential versus a standard calomel electrode of more than 0.4 volts.
• Another group of compounds for use in the present invention are nitro-substituted aromatic or heterocyclic compounds with a cathodic reduction potential versus a standard calomel electrode of more than - 1 volts.
• Especially suitable compounds are nitro - or dinitro - substituted benzimidazoles.
• Particularly useful compounds of formula (1) are:
• Particularly useful compounds of formula (2) are:
• Especially useful nitro-benimidazole compounds are:
• a stop bath is used between the development step and the silver bleaching step.
• the holographic material is washed after the silver bleaching step and before the treatment of the material in an aqueous solution of a compound which has a cathodic reduction potential versus a standard calomel electrode of more than - 1 volt.
• the time interval between the silver bleaching step and the step of treating the holographic material with an aqueous solution of a compound of formulae (1) or (2) may be several months or even years.
• the silver bleaching step may be any process of removing the developed silver but which leaves the unexposed silver halide in situ. It is to be understood that the developed silver may be converted to silver halide some of which may remain in the holographic material.
• bleaching techniques are solvent bleaching methods in which the developed silver is removed from the material and rehalogenating bleaching methods, in which the developed silver is converted to silver halide.
• Compound G has been described in L.F.A. Mason's Photographic Processing Science. Focal Press 1975 edition as being of use as an antifoggant in a silver halide developing solution.
• the object of this additive is to retard development to some extent and so prevent fogging.
• use of Compound G is entirely different to its proposed use in the prevent invention.
• the silver halide in the holographic material will be predominantly silver bromide having an average grain size of 0.02 to 0.1 ⁇ m.
• the material is inherently low scattering because of the grain size. Any photographic type fog is removed during the bleaching and fixing steps. As the silver halide in the exposed areas is converted to developed silver, oxidised and then fixed out a net shrinkage of emulsion layer and compression of the interference fringe spaceing occurs. This causes a shift to shorter wavelength between the exposure wavelength and the replay wavelength when the hologram is made as a reflection holgram.
• Holographic material was prepared by coating onto a transparent photographic film base a gelatino silver halide emulsion which was substantially pure silver bromide having a mean crystal size of 0.03 ⁇ m at a silver coating weight of 30mg/dm2.
• the emulsion was optically sensitised with a red sensitising dye so that it was optically sensitive to 633mm the colour of a He:Ne laser.
• This material was holographically exposed using a Denisyuk exposure method using a brushed aluminium plate as an object to yield (after processing) a reflective hologram.
• Strips of the dried material were then transferred to an accelerated light-stability tester called a Xenotester in which 12 days is equivalent to 120 days of normal daylight. The strips were then examined and substantially no print-out of the residual silver halide could be observed. On a Macbeth Densitometer the average density reading of the strip was 0.03.
• Example 1 Another example of holographic material was prepared as in Example 1. After a similar holographic exposure it was developed, bleached and washed as set forth in Example 1. The density of this film at a corner was then measured.
• the hologram was then attached to a window for 2 months to allow silver print-out to occur.
• the film was then cut into two and one half of the film was treated for 2 minutes in an aqueous solution of compound E at a strength of 2g/litre. After this treatment this half of the film had a pale yellow appearance compared with the other half of the film which had a blackish appearance due to silver print-out.
• Density of whole hologram before being attached to window was 0.08. Density of half holographic film treated with solution of compound E was 0.07 Density of half of holographic film not treated with solution of compound E was 0.31.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Holo Graphy (AREA)
• Silver Salt Photography Or Processing Solution Therefor (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Applications Claiming Priority (2)

Publications (2)

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ID=10582735

Family Applications (1)

Country Status (3)

Cited By (1)

Family Cites Families (1)

• 1985
  • 1985-07-23 GB GB858518602A patent/GB8518602D0/en active Pending
• 1986
  • 1986-07-17 EP EP86810321A patent/EP0210134A3/fr not_active Withdrawn
  • 1986-07-22 JP JP17097486A patent/JPS6223081A/ja active Pending

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