Radiation imagery chemistry: process – composition – or product th – Nonradiation sensitive image processing compositions or... – Fixer
Reexamination Certificate
2001-10-30
2003-04-01
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Nonradiation sensitive image processing compositions or...
Fixer
Reexamination Certificate
active
06541190
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to photography. More particularly, it relates to a photographic fixing composition, and to a method of processing color photographic silver halide elements using that composition.
BACKGROUND OF THE INVENTION
The basic image-forming process of color silver halide photography comprises the exposure of a silver halide color photographic recording material to actinic radiation (such as light) and the manifestation of a useful image by wet chemical processing of the material. The fundamental steps of this wet processing include color development to reduce silver halide to silver and to produce dye images in exposed areas of the material. During or after bleaching to oxidize metallic silver to silver(I), the silver ion is generally removed by dissolving it in a silver solvent, commonly known as a fixing agent.
In some photochemical processes, bleaching and fixing are combined in a bleach-fixing step using a composition that includes both a bleaching agent to oxidize metallic silver and a fixing agent to dissolve the remaining silver ion.
A wide variety of fixing agents and silver solvents are known, as described for example in U.S. Pat. No. 5,633,124 (Schmittou et al.) and publications noted therein. Thiosulfate salts are generally preferred as fixing agents because they are inexpensive, highly water soluble, non-toxic, non-odorous, and stable over a wide pH range. Thus, fixing is usually accomplished using a thiosulfate fixing agent that diffuses into the element, and forms silver thiosulfate complex that diffuses out of the element. In large photofinishing labs, the elements are usually immersed in a fixing solution for from 4 to 6 minutes. In small minilabs, the fixing time is shorter, that is from 90 to 120 seconds.
Fixing compositions are generally buffered to a pH of from about 4 to about 8 to achieve maximum silver “fixing” using common buffering agents such as acetic acid, succinic acid, or malic acid. They also usually include sulfite ions to serve as a silver halide solvent, to help control pH, and to act as a preservative. While such fixing compositions are effective for their intended purpose, they may have objectionable odor and keeping problems as decomposition reactions can form sulfur.
Thus, there is a need for a highly effective photographic fixing composition that has reduced odor and improved keeping stability.
SUMMARY OF THE INVENTION
This invention provides a photographic fixing composition that has a pH of from about 4 to about 12 when in aqueous form, and comprises:
at least 0.05 mol/l of a thiosulfate fixing agent,
at least 0.01 mol/l of sulfite ions, and
at least 0.025 mol/l of a phthalic acid or a salt thereof.
This invention also provides a method for providing a color photographic image comprising contacting a color developed color photographic silver halide material with the photographic fixing composition described above.
In another embodiment, a method for providing a color photographic image comprises:
A) color developing an imagewise exposed color photographic silver halide material in a predetermined volume of an aqueous color developing composition in a processing chamber, and
B) without removing the predetermined volume of the aqueous color developing composition or the color photographic silver halide material from the processing chamber, adding a predetermined volume of the photographic fixing composition described above to the processing chamber to provide a combined aqueous color development/fixing composition, and fixing the color photographic silver halide material.
Further embodiments include an additional step of:
C) without removing the combined aqueous color development/fixing composition or the color photographic silver halide material from the processing chamber, adding a predetermined volume of a photographic bleaching composition to the processing chamber to provide a combined aqueous color development/fixing/bleaching composition, and bleaching the color photographic silver halide material.
The photographic fixing composition of this invention has been shown to have improved keeping stability and reduced odor without diminishing its photographic processing properties. These advantages are achieved by using a phthalic acid or a salt thereof in the fixing composition.
DETAILED DESCRIPTION OF THE INVENTION
The photographic fixing compositions of this invention generally have a pH of from about 4 to about 12 when in aqueous form. Preferably, the pH is from about 4 to about 8, and more preferably, it is from about 4.5 to about 7.
The photographic fixing composition can be packaged and transported as a dry or liquid formulation, working strength solution, or as a single-part concentrated composition. It can be used as a replenisher as well as the initial tank working solution. Preferably, the photographic fixing composition is provided in aqueous form.
It should be understood that the photographic fixing compositions of this invention are intended for rapid and efficient removal of silver(I) from color photographic elements, either before, during or after bleaching, or any combination of these. Preferably, however, the fixing compositions have fixing activity only (no purposely added bleaching agents), and the only bleaching agents that may be present in the fixing composition are those carried over from a preceding bleaching solution by the photographic element being processed.
The first essential component in the photographic fixing composition comprises one or more thiosulfate fixing agents. The thiosulfate can be any of sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, lithium thiosulfate, calcium thiosulfate, or magnesium thiosulfate, or mixtures thereof such that a desired concentration of thiosulfate ion is provided. Preferably, ammonium thiosulfate or sodium thiosulfate (or a mixture thereof) is used. For rapid fixing, ammonium thiosulfate is preferably used.
Optionally, one or more thiocyanate fixing agents can also be present as a fixing agent especially for more rapid silver removal. If present, it can be provided as sodium thiocyanate, potassium thiocyanate or ammonium thiocyanate, or mixtures thereof. Preferably ammonium or sodium thiocyanate (or mixtures thereof) is used. The thiosulfates and thiocyanates can be obtained from a number of commercial sources or prepared using conventional starting materials and synthetic procedures.
A second essential component of the photographic fixing composition is a source (or mixture of sources) of sulfite ions. Useful salts that provide sulfite ions include but are not limited to sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, sodium metabisulfite, potassium metabisulfite, and mixtures of such salts such that the desired sulfite concentration is obtained.
The third essential component of the photographic fixing composition is a phthalic acid or a salt thereof. By “a phthalic acid”, we mean to include substituted phthalic acids. Preferred salts of phthalic acid include hydrogen phthalates such as sodium hydrogen phtbalate, potassium hydrogen phthalate, ammonium hydrogen phthalate, lithium hydrogen phthalate, sodium phthalate, and potassium phthalate. Potassium hydrogen phthalate and sodium hydrogen phthalate are preferred. Mixtures of two or more of these compounds can also be used.
The concentrations (general and preferred) of the three essential components of the photographic fixing composition of this invention are listed in TABLE I below wherein all of the ranges of concentrations are considered to be approximate (that is “about”).
TABLE I
GENERAL AMOUNT
PREFERRED
COMPONENT
(mol/l)
AMOUNT (mol/l)
Thiosulfate fixing agent
0.05 to 5
0.1 to 4
Sulfite ions
0.01 to 1
0.03 to 0.5
Phthalic acid or salt
0.025 to 1
0.025 to 0.75
thereof
If a thiocyanate fixing agent is also present in the photographic fixing composition, it is generally present in an amount of from about 0.05 to about 5 mo/l.
Optional addenda that can be present in the photographic fixing composition if desired are materials
Feller Therese M.
Haye Shirleyanne E.
Huston Janet M.
Schmittou Eric R.
Eastman Kodak Company
Le Hoa Van
Tucker J. Lanny
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