Patents by Inventor Krishnan Chari

Krishnan Chari has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6132943
    Abstract: A multilayer silver halide color photographic element is disclosed comprising a support bearing a light-sensitive silver halide emulsion layer and a non-diffusible yellow-colored magenta dye-forming masking coupler of the following formula ##STR1## wherein COUP is a magenta dye-forming coupler having the azo group attached to its coupling position; q is an integer of from 0 to 3, and each R' independently represents a substituent group or two R' groups together complete a ring of from 5-7 atoms, which ring may include 1 or more heteroatoms selected from O, N and S; m is 1 or 2, and DG represents a substituent of the formula ##STR2## where each L.sup.1 represents a divalent linking group, preferably --O(CH.sub.2).sub.y --, --NHCO(CH.sub.2).sub.y --, or --NRCO(CH.sub.2).sub.y --, where R represents an alkyl or aryl group and y represents an integer from 1 to 4; each k is either 0 or 1; each L.sup.2 represents --NHSO.sub.2 --, --NHCO--, --SO.sub.2 NH--, or --CONH--, preferably at least one L.sup.
    Type: Grant
    Filed: October 14, 1999
    Date of Patent: October 17, 2000
    Assignee: Eastman Kodak Company
    Inventors: Janet N. Younathan, Michael W. Crawley, Krishnan Chari
  • Patent number: 6074812
    Abstract: A method for desalting and dewatering a silver halide emulsion comprising removing soluble salts from the silver halide emulsion by electrodialysis, wherein the electrodialysis is carried out by passing a feed stream of the emulsion between an anion-exchange membrane and a cation-exchange membrane while a direct current voltage is applied between the anion-exchange and cation-exchange membranes so that ions are removed from the feed stream and transferred to a waste stream on the sides of the anion-exchange and cation-exchange membranes opposite to the feed stream, wherein a soluble material is added to the waste stream at a higher concentration with respect to the feed stream so as to establish a concentration gradient between the waste stream and the feed stream which drives osmotic dewatering of the feed stream during electrodialysis.
    Type: Grant
    Filed: May 14, 1999
    Date of Patent: June 13, 2000
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari
  • Patent number: 6010839
    Abstract: A multilayer silver halide color photographic element is disclosed comprising a support bearing a light-sensitive silver halide emulsion layer and a non-diffusible yellow-colored magenta dye-forming masking coupler of the following formula ##STR1## wherein COUP is a magenta dye-forming coupler having the azo group attached to its coupling position; ARYL represents an aromatic group, including optionally further substituted phenyl, naphthyl or heteroaryl groups; m represents an integer of from 1 to 4; each L.sup.1 represents a divalent linking group, preferably --O(CH.sub.2).sub.y --, --NHCO(CH.sub.2).sub.y --, or --NRCO(CH.sub.2).sub.y --, where R represents an alkyl or aryl group and y represents an integer from 1 to 4; each k is either 0 or 1; each L.sup.2 represents --NHSO.sub.2 --, --NHCO--, --SO.sub.2 NH--, or --CONH--, preferably at least one L.sup.2 group being --NHSO.sub.2 -- or --SO.sub.2 NH--, more preferably --NHSO.sub.2 --; each Z represents --SO.sub.3 M or --PO.sub.
    Type: Grant
    Filed: June 26, 1998
    Date of Patent: January 4, 2000
    Assignee: Eastman Kodak Company
    Inventors: Michael W. Crawley, Krishnan Chari, Allan F. Sowinski
  • Patent number: 5830632
    Abstract: Photographic element are described comprising a support bearing a photographic silver halide emulsion layer having associated therewith a micro-precipitated dispersion of a high dye-yield coupler having the formula:COUP--(T).sub.m --L--DYEwhere COUP is the coupler moiety of the coupler capable of reacting at the coupling position with oxidized color developer to form a first dye, T is one or more timing groups with m=0, 1 or 2, L is a linking group selected from the group consisting of --OC(O)--, --OC(S)--, --SC(O)--, --SC(S)--, or --OC(.dbd.NSO.sub.2 R)--, where R is a substituted or unsubstituted alkyl or aryl group, and DYE is a second dye or precursor thereof comprising an electrically neutral chromophore. The invention also provides a photographic coupler dispersion, a photographic silver halide emulsion, and a process for forming an image in a photographic element in accordance with the invention.
    Type: Grant
    Filed: October 31, 1996
    Date of Patent: November 3, 1998
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, David Thomas Southby, David Hoke
  • Patent number: 5770352
    Abstract: The invention is accomplished by providing an aqueous dispersion of a photographic coupler by precipitation from a solvent solution by solvent and/or pH shift. A second aqueous dispersion of an activating permanent solvent for the photographic coupler is also provided. The dispersion of activating permanent solvent and photographic coupler are combined to form a combined dispersion with relatively low amounts of coupler solvent which may be then mixed with a gelatin dispersion of silver halide particles to form a photographic emulsion coating composition suitable for casting as a photographic element layer. The coupler is selected to have a logP greater than or equal to about 10 and the activating solvent is selected to have a logP greater than or equal to about 8 and a Tg less than or equal to about -80.degree. C. to provide stable, small size photographically active coupler dispersions without the need for nonionic water soluble polymers and with minimal amount of added solvent.
    Type: Grant
    Filed: April 18, 1996
    Date of Patent: June 23, 1998
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari
  • Patent number: 5627017
    Abstract: Low melting point epoxy scavenger compounds are disclosed which contain a pH dependent ionizable group to facilitate migration of the scavenger from an adjacent scavenger layer (that does not contain any coupler) to an imaging layer (containing coupler and emulsion) of a photographic element at the pH of development. One aspect of the invention comprises a process of forming an aqueous dispersion of an epoxy compound of the structural formula SI: ##STR1## wherein: R is H, an alkyl group, or an aryl group; L.sub.1 is an alkyl group or an aryl group; L.sub.2 is --O--, --CO--, --S--, --SO.sub.2 --, --PO.sub.2 --, --CO.sub.2 --, --NHCO-- or --NHSO.sub.2 --, wherein L.sub.2 may be orientated in either direction; L.sub.3 is an alkyl group; m is 0 or 1; p is 0 or 1; and X is ##STR2## wherein R' is H or an alkyl or aryl group, with the proviso that where L.sub.2 comprises an ionizable group, X may also be an alkyl group or an aryl group; wherein the compound has a melting point of less than about 50.degree. C.
    Type: Grant
    Filed: April 25, 1995
    Date of Patent: May 6, 1997
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Paul P. Spara, Sundaram Krishnamurthy
  • Patent number: 5620632
    Abstract: A process for preparing a solid particle dispersion of an epoxy compound of the formula SI, ##STR1## wherein R is H, an alkyl group, or an aryl group; L.sub.1 is an alkylene group or an arylene group; L.sub.2 is --O--, --CO--, --S--, --SO.sub.2 --, --PO.sub.2 --, --CO.sub.2 --, --NHCO-- or --NHSO.sub.2 --, wherein L.sub.2 may be orientated in either direction; L.sub.3 is an alkylene group; m is 0 or 1; p is 0 or 1; and X is ##STR2## wherein R' is H or an alkyl or aryl group, with the proviso that where L.sub.2 comprises an ionizable group, X may also be an alkyl group or an aryl group is disclosed. The process comprising the steps of: (a) forming a coarse aqueous slurry of solid particles of said compound; and (b) milling said slurry in the presence of a hydrophobic, photographically inert, liquid second component which has a logP.sub.(calc) greater than about 6.0 for time sufficient to provide particles of the desired average particle size.
    Type: Grant
    Filed: April 25, 1995
    Date of Patent: April 15, 1997
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari
  • Patent number: 5597685
    Abstract: Color photographic element comprising residual magenta coupler scavenger ionizable epoxy compounds in combination with a specific class of image stabilizers are disclosed. Such elements comprise a support bearing thereon: (a) a photosensitive first layer comprising (i) a silver halide emulsion, (ii) a magenta coupler dispersion, and (iii) an image stabilizer of the following formula STG-A: ##STR1## wherein R.sub.1 represents an alkyl group, a cycloalkyl group, an alkenyl phenyl group, an aryl group, a heterocyclic group, an acyl group, a bridged hydrocarbon group, an alkyl sulfonyl group or an aryl sulfonyl group; R.sub.
    Type: Grant
    Filed: April 25, 1995
    Date of Patent: January 28, 1997
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Wendell F. Smith, Jr.
  • Patent number: 5543276
    Abstract: Thermal and photochemical yellowing of a color photographic element, such as a color print, is inhibited by incorporating into the photographic element an ionizable epoxy compound having the formula: ##STR1## wherein: R is H, alkyl, substituted alkyl, aryl, or substituted aryl;L.sub.1 is alkyl, substituted alkyl, aryl, or substituted aryl;L.sub.2 is O, CO, S, SO.sub.2, PO.sub.2, C(O)O, NHCO or NHSO.sub.2 ;L.sub.3 is alkyl or substituted alkyl;m is 0 or 1;p is 0 or 1;X is selected from the group consisting of ##STR2## wherein: R' is H, alkyl, substituted alkyl, aryl or substituted aryl,or, if L.sub.2 comprises an ionizable group, X is alkyl, substituted alkyl, aryl or substituted aryl.
    Type: Grant
    Filed: June 8, 1994
    Date of Patent: August 6, 1996
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Wendell F. Smith, Jr., Paul P. Spara, Sundaram Krishnamurthy
  • Patent number: 5508147
    Abstract: Yellowing of a processed photographic element is inhibited by incorporating a scavenger comound capable of reacting with magenta coupler, e.g. an epoxy compound, in a layer adjacent a layer containing the magenta coupler. In a preferred embodiment, the magenta coupler containing layer is sandwiched between layers containing the scavenger compound. Prior to processing at least one of these layers contains a solubilizing agent for the scavenger compound. In preferred embodiments, the processing solution used to process the photographic element containing an external solubilizing agent for the scavenger compound, preferably benzyl alcohol.
    Type: Grant
    Filed: January 4, 1993
    Date of Patent: April 16, 1996
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Wendell F. Smith, Sundaram Krishnamurthy
  • Patent number: 5476756
    Abstract: Yellowing of a processed photographic element is inhibited by incorporating a scavenger compound capable of reacting with magenta coupler, e.g. an epoxy compound, in a layer adjacent a layer containing the magenta coupler. At least one of these layers contains a solubilizing agent for the scavenger compound. In preferred embodiments, the processing solution used to process the photographic element contains an external solubilizing agent for the scavenger compound, preferably benzyl alcohol.
    Type: Grant
    Filed: June 8, 1994
    Date of Patent: December 19, 1995
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Wendell F. Smith, Sundaram Krishnamurthy
  • Patent number: 5451497
    Abstract: The tendency of a photographically useful compound (PUC) to crystallize when dispersed in an aqueous medium is inhibited by codispersing with the PUC a non-color forming, oil-soluble, monomeric or oligomeric organic compound having a glass transition temperature between 0.degree. and 150.degree. C. Preferred organic compounds are oil-soluble sucrose esters, such as sucrose octaacetate, and rosin and derivatives thereof.
    Type: Grant
    Filed: December 30, 1993
    Date of Patent: September 19, 1995
    Assignee: Eastman Kodak Company
    Inventors: David D. Miller, Krishnan Chari
  • Patent number: 5426019
    Abstract: Yellowing, dye fade and thermal pinking of a processed color photographic element is improved by incorporating into the photographic element a non-color forming, oil-soluble, monomeric or oligomeric organic compound having a glass transition temperature between 0.degree. and 150.degree. C. Preferred organic compounds include rosin derivatives, natural resins and oil-soluble sucrose esters, etc. In a particularly preferred embodiment, the above-noted properties are improved by incorporating into the photographic element an oil-soluble rosin derivative, such as abietic acid.
    Type: Grant
    Filed: December 30, 1993
    Date of Patent: June 20, 1995
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari
  • Patent number: 5283167
    Abstract: A direct-positive image-forming photographic material comprises a supporting substrate bearing a light sensitive, nonprefogged silver halide photographic emulsion capable of forming an internal latent image and includes a water-insoluble nucleator. The nucleator is incorporated in the photographic material in the form of a solid particle dispersion to improve the storage stability of the photographic material. The development rate of the photographic material may be increased by use of a developer containing an activator for the nucleator.
    Type: Grant
    Filed: January 30, 1992
    Date of Patent: February 1, 1994
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Douglas E. Corbin, Glenn M. Brown, Harry A. Hoyen
  • Patent number: 5256527
    Abstract: The invention provides stable dispersions of couplers and methods of their formation. The stable dispersions are formed by the use of a nonionic water soluble polymer in combination with an anionic surfactant having a sulfate or sulfonate head group and a hydrophobic group of 8 to 20 carbons. The preferred nonionic water soluble polymers are polyethyleneoxide and polyvinylpyrrolidene. It is preferred that the dispersions have a pH of between about 5 and 5.5.
    Type: Grant
    Filed: September 9, 1991
    Date of Patent: October 26, 1993
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, James T. Beck
  • Patent number: 5190851
    Abstract: A color photographic silver halide negative working duplicating element comprising a support having thereon at least one red-sensitive photographic silver halide emulsion layer comprising at least one cyan image-dye forming coupler; at least one green-sensitive photographic silver halide emulsion layer comprising at least one magenta image-dye forming coupler; and, at least one blue-sensitive photographic silver halide emulsion layer comprising at least one yellow image-dye forming coupler, provides improved images when (a) at least one of the layers comprises a unit of at least two layers including a first layer and a second layer, the first layer having a higher photosensitivity than the second layers and being farther from the support than the second layers; (b) the first layers contain an image-dye forming coupler in an amount insufficient to react with all the oxidized developer formed during development after maximum exposure; (c) the image-dye forming couplers of the first layers being in a dispersion
    Type: Grant
    Filed: December 21, 1990
    Date of Patent: March 2, 1993
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, John T. Keech, John F. Sawyer, Jeffrey W. Schmoeger, Paul L. Zengerle
  • Patent number: 5087554
    Abstract: The invention provides stable dispersions of couplers and methods of their formation. The stable dispersions are formed by the use of a nonionic water soluble polymer in combination with an anionic surfactant having a sulfate or sulfonate head group and a hydrophobic group of 8 to 20 carbons. The preferred nonionic water soluble polymers are polyethyleneoxide and polyvinylpyrrolidene. It is preferred that the dispersions have a pH of between about 5 and 5.5.
    Type: Grant
    Filed: June 27, 1990
    Date of Patent: February 11, 1992
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, James T. Beck
  • Patent number: 5015564
    Abstract: The invention provides stable dispersions of couplers and methods of their formation. The stable dispersions are formed by the use of a nonionic water soluble polymer in combination with an anionic surfactant having a sulfate or sulfonate head group and a hydrophobic group of 8 to 20 carbons. The preferred nonionic water soluble polymers are polyethyleneoxide and polyvinylpyrrolidene.
    Type: Grant
    Filed: June 1, 1990
    Date of Patent: May 14, 1991
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari
  • Patent number: 5008179
    Abstract: The invention is accomplished by providing an aqueous dispersion of a photographic coupler by precipitation from a solvent solution by solvent and/or pH shift. A second aqueous dispersion of an activating permanent solvent for the photographic coupler is also provided. The dispersion of activating permanent solvent and photographic coupler are combined to form a combined dispersion which is mixed with a gelatin dispersion of silver halide particles to form a photographic emulsion suitable for casting as a photographic element. In a preferred method of the invention, the activating solvent is incorporated into a dispersion of latex particles prior to being combined with the dispersion of photographic coupler.
    Type: Grant
    Filed: November 22, 1989
    Date of Patent: April 16, 1991
    Assignee: Eastman Kodak Company
    Inventors: Krishnan Chari, Wayne A. Bowman, Brian Thomas
  • Patent number: 4957857
    Abstract: The invention provides stable dispersions of couplers and methods of their formation. The stable dispersions are formed by the use of a nonionic water soluble polymer in combination with an anionic surfactant having a sulfate or sulfonate head group and a hydrophobic group of 8 to 20 carbons. The preferred nonionic water soluble polymers are polyethyleneoxide and polyvinylpyrrolidene.
    Type: Grant
    Filed: December 23, 1988
    Date of Patent: September 18, 1990
    Assignee: Eastman Kodak Company
    Inventor: Krishnan Chari