Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-04-24
2003-10-07
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S567000
Reexamination Certificate
active
06630292
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention is directed to improvements in the silver halide based photography.
The principle of silver halide photography is based on the activation of silver halide grains by light. A method to reduce the amount of silver present, without loss of the specific surface area of the grains in the photographic layers, is realisable by the use of tabular grains. Tabular grains in general (for which the diameter is considerably larger than the thickness) are also preferred for raising the speed of a silver halide emulsion for photographic purposes, increasing sharpness, and improving graininess, colour sensitivity efficiency with sensitising dyes and covering power. The high bromide {111} tabular grains are commonly used in the photographic industry. Still, there is a need to produce tabular crystals with a high aspect ratio and a narrow size distribution. A Grain Growth Modifiers (GGM) can narrow the size distribution and increase the aspect ratio.
Definitions
In the present description the following terms and definitions are used.
In referring to grains and emulsions containing one or more halides, the halides are named in order of ascending concentrations
The term “high chloride” in referring to grains and emulsions indicates that chloride is present in a concentration of greater than 50 mole percent, based on total silver.
The term “high bromide” in referring to grains and emulsions indicates that bromide is present in a concentration of greater than 50 mole percent, based on total silver.
The term “equivalent circular diameter” or “ECD” is employed to indicate the diameter of a circle having the same projected area as the silver halide grain.
The term “aspect ratio” designates the ratio of the grain ECD to the grain thickness.
The term “tabular grain” indicates a grain having two parallel grain faces which are clearly larger than any remaining grain face and an aspect ratio of at least 2.
The term “tabular grain emulsion” refers to an emulsion in which tabular grains account for greater than 50 percent of the total grain projected area.
The term “{111} tabular” is employed in referring to tabular grain emulsions containing tabular grains having {111} major faces.
Octahedral grains with respect to high chloride-containing grains means eight-sided silver chloride-containing grains whose exterior crystal faces lie in {111} crystallographic planes and are normal to axes of trigonal symmetry.
The term “pBr”=−log[Br
−
]
Cubo-octahedral grains with respect to high silver chloride-containing grains means fourteen-sided silver chloride-containing grains of which eight of the exterior crystal faces lie in {111} crystallographic planes and six of the exterior crystal faces lie in {100} crystallographic planes.
The grain making process is: the process of making grains that contains at least the nucleation phase (reacting a water-soluble silver salt and at least one water-soluble halide salt) and optional ripening and/or growth phases (addition of reagents).
Water Solubility: values are given at 25 degrees C. or at the nearest temperature to this where data are available. The solubility of solids is defined as the concentration of the compound in a solution that is in equilibrium with the solid phase at the specified temperature and one atmosphere pressure. For liquids whose water mixtures separate into two phases, the solubility given here is the concentration of the compound in the water-riche phase at equilibrium.
High chloride {111} crystal surfaces ({111} tabular and octahedral grains) can only be produced in the presence of a GGM. The reason for this is that high silver chloride {111} crystal surfaces, unlike high bromide {111} crystal surfaces, cannot be formed or maintained in the absence of a GGM, but rather take cubic forms, since {100} crystal faces are more stable in high silver chloride grains
High chloride grains with {111} crystal surfaces are of practical importance because they present a unique surface arrangement of silver and halide ions, which in turn influence the grain surface reaction and adsorption typically encountered in photographic applications. For high chloride {111} tabular grains a shortening of processing time is greatly desired and there is an urgent need for the development of silver halide.
GGM can be used to increase the aspect ratio for high bromide silver halide grain emulsions and to form tabular- and octahedral grains for high chloride silver halide grain emulsions.
The technology used presently in the prior art methods can be divided in three main groups:
According to the first method, high bromide {111} tabular grain emulsions are used.
The preparation of high bromide {111} tabular grain emulsions with the aid of GGM is mainly described in the patents: U.S. Pat. No. 5,411,851 (and EP 0,701,166); U.S. Pat. Nos. 5,411,853 and 6,418,125
In all these patents the composition of the {111} tabular grains depends on the composition of the grains from the initial crystallisation process, which is the nucleation phase. The patent (U.S. Pat. No. 5,411,851) disclose a method in which the ripened grains will be tabular, independent of the initial shape of the grains, when the initial thickness of the tabular grains after the nucleation phase is 0.06 &mgr;m or less. During the nucleation phase the pBr is about 3.8. No additions of chemical reagents (silver nitrate nor potassium bromide) are performed to the reaction chamber after the nucleation phase, except for pH- and pBr-correction (e.g. pH=5.0 and pBr≈3.1). This means that the composition of the grain is determined by the reagents additions during the nucleation phase and can not be steered in one of the ripening phases (=physical- and/or Ostwald-ripening phases).
The main aspects of these known processes are:
U.S. Pat. No. 5,411,851: The GGM used in this patent are: tri-amino pyrimidine derivatives. The temperature during the nucleation phase is: =15° C., and the pH range is: 4.6<pH<9.0.
U.S. Pat. No. 5,411,853 and EP 0,701,166: The GGM used in these patents are poly iodo phenol derivatives. The temperature during the nucleation phase is: 40° C., and the pH range is: 1.5<pH<8.
U.S. Pat. No. 5,418,125: The GGM used in this patent are: hydroxy quinoline derivatives. The temperature during the nucleation phase is: =40° C., and the pH range is: 2<pH<8.
According to Maskasky (U.S. Pat. Nos. 5,418,125; 5,411,851; 5,411,853 and EP 0 701 166 A1) it not understand why the grain growth process with double-jet precipitation of chemical reagents employing this grain growth modifiers are less effective than the grain growth process of his invention.
The process as described in prior art patents from Maeskssy is schematically described in FIG.
1
.
The main disadvantages, for Maskasky's system, as compared to the commonly used double-jet precipitation method, are:
1. The process described by Maskasky has only a nucleation stage in which silver and halide reagents are added. This implies that no grains with a shell layer having different halide compositions can be formed. Those core/shell grains are commonly employed in all photographic products because each layer can add to the unique photographic properties of the product. Therefore the double-jet method gives a better control over the crystal growth making process in which the photographic properties can be maximally utilised.
2. The used GGM are in general not very well soluble in water and can only be removed from the grains with special solvents and/or reduction of the pH (protonation), U.S. Pat. No. 5,418,125. The incomplete removal of the GGM from the grain surface will negatively influence the photographic properties. This will give an emulsion with higher fog or lower sensitivity. This is because spectral sensitizers can not effectively form aggregates onto the grain surface.
3. The m
Baxter Janet
Fuji Photo Film B.V.
Merchant & Gould P.C.
Walke Amanda C
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