Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Silver compound sensitizer containing
Reexamination Certificate
2001-04-03
2002-12-10
Baxter, Janet (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Silver compound sensitizer containing
C430S569000, C430S611000
Reexamination Certificate
active
06492101
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of water-soluble disulfide compounds in the preparation of monodisperse regular (non-tabular) grain light-sensitive silver halide emulsions.
BACKGROUND OF THE INVENTION
Problems with fogging have plagued the photographic industry from its inception. Fog is a deposit of silver or dye that is not directly related to the image-forming exposure, i.e., when a developer acts upon an emulsion layer, some reduced silver is formed in areas that have not been exposed to light. Fog can be defined as a developed density that is not associated with the action of the image-forming exposure, and is usually expressed as “D-min”, the density obtained in the unexposed portions of the emulsion. Density, as normally measured, includes both that produced by fog and that produced as a function of exposure to light. It is known in the art that the appearance of photographic fog related to intentional or unintentional reduction of silver ion (reduction sensitization) can occur during many stages of preparation of the photographic element including silver halide emulsion preparation, spectral/chemical sensitization of the silver halide emulsion, melting and holding of the liquid silver halide emulsion melts, subsequent coating of silver halide emulsions, and prolonged natural and artificial aging of coated silver halide emulsions.
The control of fog, whether occurring during the formation of the light-sensitive silver halide emulsion, during the spectral/chemical sensitization of those emulsions, during the preparation of silver halide compositions prior to coating on an appropriate support, or during the aging of such coated silver halide compositions, has been attempted by a variety of means. Mercury-containing compounds, such as those described in U.S. Pat. Nos. 2,728,663; 2,728,664; and 2,728,665, have been used as additives to control fog. Thiosulfonates and thiosulfonate esters, such as those described in U.S. Pat. Nos. 2,440,206; 2,934,198; 3,047,393; and 4,960,689, have also been employed. Organic dichalcogenides, for examples the disulfide compounds described in U.S. Pat. Nos. 1,962,133; 2,465,149; 2,756,145; 2,935,404; 3,184,313; 3,318,701; 3,409,437; 3,447,925; 4,243,748; 4,463,082; and 4,788,132 have been used not only to prevent formation of fog but also as desensitizers and as agents in processing baths and as additives in diffusion transfer systems. More recently, U.S. Pat. No. 5,364,754 describes the use of primarily water-insoluble organic dichalcogenides during the preparation of silver halide crystals to modify the grain growth of silver hlaide crystals in addition to preventing formation of fog without a concomitant large loss in sensitivity. U.S. Pat. No. 5,418,127 describes the use of certain water soluble disulfide compounds which provide the combined attributes of high water solubility and strong antifogging activity with de minimus impact on sensitivity.
A problem has been discovered when attempting to employ some of the water soluble disulfide compounds described in U.S. Pat. No. 5,418,127 in the preparation of monodisperse conventional regular grain silver halide high bromide emulsions. Regular grains are three-dimensional (non-tabular) grains which are substantially internally free of crystal plane stacking faults. Specifically, it has been discovered that the presence of some of such compounds during the precipitation of such emulsion grains lead to the formation of a significant fraction of large grain contamination, generally due to formation of some larger tabular grains. It would be desirable to provide a process for the preparation of monodisperse regular grain emulsions which would enable the use of water soluble disulfide compounds in order to take advantage of the combined attributes of high water solubility and strong antifogging activity with only minimal impact on sensitivity, while avoiding the disadvantages of large grain contamination when emulsion grain size monodispersity is desired.
SUMMARY OF THE INVENTION
This invention provides a method of making a monodisperse regular grain silver halide high bromide emulsion comprising precipitating regular silver halide grains comprising greater than 50 mole percent bromide, based on total silver, in a reaction vessel, and adding to the reaction vessel before or during precipitation a disulfide compound represented by the following formula (I):
where Y and Z are H atoms or substituents, which may be connected to form a carbocyclic or heterocyclic ring; X is —O—, —NH— or —NR—, where R is a substituent; M is —H— or a cationic species; and L is a linking group, where p is 0 or 1. In preferred embodiments, Y and Z are connected to form a further substituted or unsubstituted phenyl ring.
This invention further provides a silver halide emulsion prepared by the method, and a photographic element comprising a silver halide emulsion prepared by the method. The use of water soluble disulfide compounds of the above formula in the preparation of monodisperse high bromide emulsion grains in accordance with the invention provides the antifoggant advantages of the general class of compounds described in U.S. Pat. No. 5,418,127 in a monodisperse emulsion, while avoiding the problem of large grain contamination in such emulsions.
DETAILED DESCRIPTION OF THE INVENTION
The disulfide compounds employed in accordance with the invention are represented by following formula (I):
Y and Z are H atoms or substituents, which may be connected to form a carbocyclic or heterocyclic ring. In preferred embodiments, Y and Z are connected to form a further substituted or unsubstituted phenyl ring. X is independently an —O—, —NH— or —NR—. Most preferably X is —NH—. L is a linking group, and p is 0 or 1. In particularly preferred embodiments, the disulfide compound employed is of the formula (II):
Substituents represented by Y, Z and R, as well as further substituents which may be present Y and Z connect to form a further substituted phenyl ring, are selected from those which do not interfere with the intended function of the disulfide compound in the photographic emulsion and which maintains the water solubility of the compound. Examples of suitable substituents include alkyl groups (for example, methyl, ethyl, hexyl), fluoroalkyl groups (for example, trifluoromethyl), aryl groups (for example, phenyl, naphthyl, tolyl), sulfonyl groups (for example, methylsulfonyl, phenylsulfonyl). Preferred are simple alkyl groups and simple fluoroalkyl groups.
Preferably L is a unsubstituted alkylene group and is usually —(CH
2
)
n
— where n ranges from zero to 11 and is preferably 1 to 3. Other examples of L are given below:
M is either a hydrogen atom or a cationic species if the carboxyl group is in its ionized form. The cationic species may be a metal ion or an organic ion. Examples of organic cations include ammonium ions (for example, ammonium, tetramethylammonium, tetrabutylammonium), phosphonium ions (for example, tetraphenylphosphonium), and guanidyl groups. Preferably M is hydrogen or an alkali metal cation, with a sodium or potassium ion being most preferred.
Examples of disulfide compounds of formula (I) which may be employed in accordance with this invention include compounds I-A through I-G shown below.
The solubilized disulfides employed in the invention are easily prepared using readily available starting materials. Most of the solubilized disulfides can be obtained by reacting aminophenyl disulfide or hydroxyphenyl disulfide with the appropriate cyclic anhydride followed by conversion of the free diacid to its anionic form using materials such as sodium bicarbonate. Other solubilized disulfides could be obtained by reacting aminophenyl disulfide or hydroxyphenyl disulfide with the mono chloride of a dicarboxylic acid mono ester, followed by hydrolysis of the ester to the carboxylic acid. Representative synthetic examples are provided in U.S. Pat. No. 5,418,127 referenced above, the disclosure of which is incorporated herein in its entirety. Solubilized non-phenyl disulfides can si
Burgmaier George J.
Jensen Bradley K.
Kim Sang H.
Anderson Andrew J.
Baxter Janet
Eastman Kodak Company
Walke Amanda C.
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