Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2001-11-05
2003-11-11
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S432000, C430S434000, C430S531000, C430S533000, C430S536000, C430S537000, C430S961000
Reexamination Certificate
active
06645705
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to photographic imaging elements having a protective overcoat that resists fingerprints and common stains. The invention involves converting a processing-solution-permeable overcoat to a waterresistant overcoat during photochemical processing, which conversion is improved by employing, in the overcoat formulation, a compound comprising a block-copolymer chain of ethylene oxide and propylene oxide.
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 the 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. Thus, gelatin or similar natural or synthetic hydrophilic polymers have proven to be the binders of choice for silver halide photographic elements. Unfortunately, when gelatin or similar polymers are formulated so as to facilitate contact between the silver-halide crystals and aqueous processing solutions, the imaged product is not as fingerprint and stain resistant as would be desirable, particularly in view of the handling or environmental exposure commonly experienced by the pictures. The imaged product can be easily stained by common household products, such as foods or beverages; fingerprints can leave marks.
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.
Various lamination techniques are known and practiced in the trade. U.S. Pat. Nos. 3,397,980, 3,697,277 and 4,999,266 describe methods of laminating a polymeric sheet film, as a protective layer, on a processed image. U.S. Pat. No. 5,447,832 describes the use of a protective layer containing a mixture of high and low Tg latices as a water-resistant layer to preserve the antistat property of a V
2
O
5
layer through photographic processing. This protective layer is not applicable to the image formation layers, however, since it will detrimentally inhibit the photographic processing. U.S. Pat. No. 3,443,946 provides a roughened (matte) scratch-protective layer, but not one designed to be water-impermeable or resistant. U.S. Pat. No. 3,502,501 is intended to provide 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 processibility. U.S. Pat. No. 5,179,147 likewise provides an overcoat that is not water-protective.
Protective coatings that need to be applied to the image after it is formed, several of which were mentioned above, adds a significant cost to the final imaged product. Processing equipment needs to be modified and the personnel running the processing operation need to be trained to apply the protective coating. A number of patents have been directed to water-resistant protective coatings that can be applied to a photographic element prior to development. For example, 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 light-sensitive layer, 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. More recently, U.S. Pat. No. 5,853,926 to Bohan et al. discloses a protective coating for a~photographic element, involving the application of an aqueous coating comprising polymer particles and a soft polymer latex binder. This coating allows for appropriate diffusion of photographic processing solutions, and does not require a coating operation after exposure and processing. Again, however, the hydrophobic polymer particles must be fused to form a protective coating that is continuous and water-impermeable.
U.S. Pat. No. 5,856,051 describes the use of hydrophobic particles with gelatin as the binder in an overcoat formulation. This invention demonstrated 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 a coating operation after exposure and processing. The hydrophobic polymers exemplified in U.S. Pat. No. 5,856,051 include polyethylene have a melting temperature (Tm) of 55 to 200° C., and are therefore capable of forming a water-resistant layer by fusing the layer at a temperature higher than the Tm of the polymer after the sample has been processed to generate the image. The coating solution is aqueous and can be incorporated in the manufacturing coating operation without any equipment modification. Again, however, fusing is required by the photofinishing laboratories to render the protective overcoat water resistant. Similarly, commonly assigned U.S. Ser. No. 09/353,939 and U.S. Pat. No. 6,268,101, respectively, describe the use of a polystyrene-based material and a polyurethane-based material, with gelatin as the binder, in an overcoat for a photographic element, which overcoat can be fused into a water resistant overcoat after photographic processing is accomplished to generate an image.
Several methods were patented based on the concept of an overcoat composition comprising of a hydrophilic material and a hydrophobic material. The washing out of the hydrophilic component facilitates the coalescence of the hydrophobic materials in the final product, further facilitated by elevated temperatures commonly associated with drying. Various hydrophilic materials, such as non-crosslinked gelatin or polyvinylalcohol, and various hydrophobic materials, such as polyurethanes and epoxy resins, have been disclosed, for example in commonly assigned U.S. Pat. No. 6,232,049, U.S. Pat. No. 6,194,130, and U.S. Ser. No. 09/699,866.
PROBLEM TO BE SOLVED BY THE INVENTION
It has been found that imaged elements having overcoats in which a hydrophilic material is washed out during processing can suffer from the problem of wet abrasion or wet scratch when they are brought into contact with any face-side rollers in the processor or in the dryer. The hydrophilic material is washed out preliminary to conversion of the overcoat from a processing-solution permeable overcoat to a water-resistant protective overcoat. Without wishing to be bound by theory, it is believed that the overcoat may form a porous membrane, lacking physical strength and integrity, during removal of the hydrophilic material or polymer during processing. It was also noticed that some hydrophobic particles used in the overcoat can retain iron from bleach solution, resulting in a yellowish color stained image. Finally, incomplete conversion to a water-resistant protective overcoat was found to occur with some hydrophobic materials.
Therefore, it would be desirable to provide a novel overcoat that is permeable to photo-processing solution for image formation, and yet which is capable of converting to a protective overcoat for stain and f
Decker David E.
Flood Elmer C.
O'Connor Kevin M.
Yau Hwei-Ling
Eastman Kodak Company
Konkol Chris P.
Schilling Richard L.
LandOfFree
Protective overcoat for photographic elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Protective overcoat for photographic elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Protective overcoat for photographic elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3175277