Radiation imagery chemistry: process – composition – or product th – Imaged product – Multilayer
Reexamination Certificate
2001-04-30
2002-08-20
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaged product
Multilayer
C430S350000, C430S523000, C430S531000, C430S536000, C430S537000, C430S961000
Reexamination Certificate
active
06436592
ABSTRACT:
FIELD OF THE INVENTION
The present invention provides a protective overcoat for photographic elements. More particularly the present invention provides an overcoat which is permeable to processing solutions and when subsequently fused provides water resistance and scratch protection to photographic elements.
BACKGROUND OF THE INVENTION
Silver halide photographic elements contain light sensitive silver halide in a hydrophilic emulsion. An image is formed in the element by exposing the silver halide to light, or to other actinic radiation, and developing the exposed silver halide to reduce it to elemental silver.
In color photographic elements a dye image is formed as a consequence of silver halide development by one of several different processes. The most common is to allow a by-product of silver halide development, oxidized silver halide developing agent, to react with a dye forming compound called a coupler. The silver and unreacted silver halide are then removed from the photographic element, leaving a dye image.
In either case, formation of the image commonly involves liquid processing with aqueous solutions that must penetrate the surface of the element to come into contact with silver halide and coupler. Gelatin has been used exclusively in a variety of silver halide photographic systems as the primary binder due to its many unique properties, one of which is the water-swellable property. This rapid swelling allows processing chemistry to proceed and images to be formed. However, due to this same property, photographic images, whether they are on film or paper, need to be handled with extreme care so as not to come in contact with any aqueous solutions that may damage the images. Thus, although gelatin, and similar natural or synthetic hydrophilic polymers, have proven to be the binders of choice for silver halide photographic elements to facilitate contact between the silver halide crystal and aqueous processing solutions, they are not as tough and mar-resistant as would be desired for something that is handled in the way that an imaged photographic element may be handled. Thus, the imaged element can be easily marked by fingerprints, it can be scratched or tom and it can swell or otherwise deform when it is contacted with liquids.
There have been attempts over the years to provide protective layers for gelatin based photographic systems that will protect the images from damages by water or aqueous solutions. U.S. Pat. No. 2,173,480 describes a method of applying a colloidal suspension to moist film as the last step of photographic processing before drying. A series of patents describes methods of solvent coating a protective layer on the image after photographic processing is completed and are described in U.S. Pat. Nos. 2,259,009; 2,331,746; 2,798,004; 3,113,867; 3,190,197; 3,415,670 and 3,733,293. The application of UV-polymerizable monomers and oligomers on processed image followed by radiation exposure to form crosslinked protective layer is described U.S. Pat. Nos. 4,092,173; 4,171,979; 4,333,998 and 4,426,431. One drawback for the solvent coating method and the radiation cure method is the health and environmental concern of those chemicals to the coating operator. U.S. Pat. Nos. 3,397,980; 3,697,277 and 4,999,266 describe methods of laminating polymeric sheet film on the processed image as the protective layer. U.S. Pat. No. 5,447,832 describes the use of a protective layer containing mixture of high and low Tg latices as the water-resistance layer to preserve the antistat property of the V
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layer through photographic processing. This protective layer is not applicable to the image formation layers since it will detrimentally inhibit the photographic processing. U.S. Pat. No. 2,706,686 describes the formation of a lacquer finish for photographic emulsions, with the aim of providing water- and fingerprint-resistance by coating the emulsion, prior to exposure, with a porous layer that has a high degree of water permeability to the processing solutions. After processing, the lacquer layer is fused and coalesced into a continuous, impervious coating. The porous layer is achieved by coating a mixture of a lacquer and a solid removable extender (ammonium carbonate), and removing the extender by sublimation or dissolution during processing. The overcoat as described is coated as a suspension in an organic solvent, and thus is not desirable for large-scale application. U.S. Pat. No. 3,443,946 provides a roughened (matte) scratch-protective layer, but not a water-impermeable one. U.S. Pat. No. 3,502,501 provides protection against mechanical damage only, the layer in question contains a majority of hydrophilic polymeric materials, and must be permeable to water in order to maintain processability. U.S. Pat. No. 5,179,147 likewise provides a layer that is not water-protective.
U.S. Patent 5,856,051 incorporated by reference herein, describes a protective overcoat comprising hydrophobic polymer particles that have a particular melting point range, and gelatin. After photoprocessing development to produce the image, the photographic element is thermally fused so that the hydrophobic polymer particles form a water-resistant protective overcoat. The element described in the ‘051 patent, however, suffers in that this protective overcoat is easily scratched. The present invention discloses a uniquely structured overcoat that allows the photographic processing solutions to diffuse through for image formation, and then provides water resistance and improved scratch resistance properties compared to the one described in the '051 patent.
Commonly assigned, copending USSN 09/312,378 (docket 79332), by the same inventors, discloses an imaged photographic element having a protective overcoat thereon, which protective overcoat comprises a first coating of hydrophobic polymer particles having an average size of 0.01 to 1 microns, a melting temperature of from 55 to 200° C. at a weight percent of 30 to 95, and gelatin at a weight percent of 5 to 70. A second coating of abrasion resistant particles having an average size of from 0.01 to 1 microns is applied to form a second layer over the first layer.
There remains a need for an aqueous coatable, water-resistant protective overcoat that can be incorporated into the photographic product, allows for appropriate diffusion of photographic processing solutions, and does not require coating operation after exposure and processing.
SUMMARY OF THE INVENTION
The present invention is an imaged photographic element having a protective overcoat thereon. The protective overcoat is formed by providing a photographic element having at least one silver halide light-sensitive emulsion layer. A first coating of hydrophobic polymer particles having an average size of 0.01 to 1 microns, a melting temperature of from 55 to 200 ° C. at a weight percent of 30 to 95, and gelatin or other hydrophilic polymer at a weight percent of 5 to 70 is applied to form a first layer over the silver halide light-sensitive emulsion layer. A second coating of abrasion resistant particles having an average size of from 0.01 to 1 microns is applied to form a second layer over the first layer. The coatings are dried at temperatures not exceeding the melting point of the particles used in the first coating, or of the glass transition temperature of the abrasion resistant particles used in the second coating, whichever is the lowest. The photographic element can be developed to provide an imaged photographic element. The first and second layers are fused to form a protective overcoat.
DETAILED DESCRIPTION OF THE INVENTION
The present invention describes an imaged photographic element having an overcoat that imparts both water resistance and abrasion resistance. The protective overcoat of this invention can be achieved in one of the following manners. An uppermost overcoat layer, composed of abrasion resistant particles and optionally water soluble binders and optionally a fusible wax component, is coated over a second uppermost layer, which is composed of fusible particl
Franklin Linda M.
Landry-Coltrain Christine J.
Yau Hwei-ling
Eastman Kodak Company
Konkol Chris P.
Schilling Richard L.
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