Radiation imagery chemistry: process – composition – or product th – Thermographic process – Heat applied after imaging
Reexamination Certificate
2000-10-30
2002-08-20
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Thermographic process
Heat applied after imaging
C430S444000, C430S463000, C430S531000, C430S533000, C430S536000, C430S961000
Reexamination Certificate
active
06436617
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to imaged elements having a protective overcoat that resists fingerprints, common stains, and spills. In particular, the invention is directed to a photographic element comprising an overcoat made from a water-dispersible epoxy-functional latex.
BACKGROUND OF THE INVENTION
Gelatin has been used extensively in a variety of imaging elements as the binder because of its many unique and advantageous properties. For example, its property of water swellability allows processing chemistry to be carried out to form silver halide-based photographic images, and its hydrophilic nature allows gelatin to function as an ink-receiver in ink-jet recording media. For a photographic element, an aqueous solution needs to penetrate the surface of the element to contact the silver halide and couplers necessary for dye mage formation. Therefore, water-soluble polymers or materials which have affinity for water are proven to be the binders of choice for photographic elements. However, while these materials are good for image development, they are not strong enough to resist mechanical damage such as scratching, tearing, and other types of deformation. Furthermore, the imaged elements, after image formation is complete, have very little resistance to fingerprints or to stains from food and drink spills. Imaging elements with exposed gelatin-containing materials, no matter if they are formed on transparent or reflective media, need to be handled with extreme care so as not to come into contact with aqueous solutions that may damage the images. Accidental spillage of common household solutions such as coffee, punch, or even plain water can damage imaged elements such as ink-jet, electrophotographic, or photographic prints.
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 number of patents describes methods of solvent coating a protective layer on the image after photographic processing is completed, for example, 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. U.S. Pat. No. 5,376,434 describes a protective layer formed on a photographic print by coating and drying a latex on a gelatin-containing layer bearing an image. The latex is a resin having a glass transition temperature of from 30° C. to 70° C. A drawback for a solvent coating method is the health and environmental concern of those chemicals to the coating operator.
Alternatively lamination can be used to provide an imaged element with resistance to scratch, water, and stain resistance. Lamination typically involves placing a protective layer, coated on a suitable support, onto the image which is to be protected. The support for the protective coating may remain permanently adhered to the image or it may subsequently be peeled off leaving only the protective layer adhered to the image. Lamination has several disadvantages in that it brings about an added expense associated with coating an additional support. In addition, air pockets may be trapped during the laminating step, leading to image defects.
Protective coatings that need to be applied to an image after it is formed, several of which coatings were mentioned above, add a significant cost to the final imaged product. 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, and allows for appropriate diffusion of photographic processing solutions. The hydrophobic polymers exemplified in U.S. Pat. No. 5,856,051 include polyethylene have a melting temperature (Tm) of 55 to 200° C. A layer comprised of such polymers is capable of becoming water-resistant 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 into the manufacturing coating operation without any equipment modification.
It can be seen that various approaches have been attempted to obtain an imaged imaging element with resistance to water and mechanical damages. However, the aforementioned prior art references are deficient with regard to simultaneously satisfying performance, environmental, convenience and cost requirements or preferences. Also, in recent years, the use by the public of various printing and imaging technologies on a small scale or at home is increasingly more popular. It has become increasingly more desirable to provide protection for the imaged or printed documents against abrasion, transfer cover materials, water or alcohol spills, ink smear, or other image print degradation processes and detrimental effects from the surroundings. It would be desirable to provide protection for an imaged print without needing to modify processing equipment or needing to train the personnel running the processing operation to apply the protective coating.
The objective of the present invention is to provide an imaged imaging element with a protective overcoat while avoiding the problems and limitations of the prior art. It would be especially desirable to obtain a water-resistant protective overcoat for a photographically imaged element without the addition of laminating or fusing steps, without the need for higher temperatures, and without requiring additional equipment to carry out photoprocessing.
SUMMARY OF THE INVENTION
The present invention relates to a protective overcoat for an imaged photographic element that provides water resistance, fingerprint resistance, and the like. This protective overcoat is made from an overcoat composition comprising epoxy-containing particles comprising at least 50%, by dry weight of the particle, of a solid epoxy compound or resin and which particles having a glass transition temperature of greater than 20° C. and a mean particle size of not more than 500 nm (0.5 microns). The overcoat composition further comprises, in the epoxy-containing particle, a polymer having acid groups. The overcoat composition also comprises a binder material for the epoxy-containing particles, which material comprises a hydrophilic material that is substantially soluble in the developing solution, and a hydrophobically modified associative thickener. The photographic element comprises a support, at least one silver-halide emulsion
Bello James L.
Kestner Melvin M.
O'Connor Kevin M.
Wang Yongcai
Eastman Kodak Company
Konkol Chris P.
Schilling Richard L.
LandOfFree
Protective epoxy overcoat for imaging 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 epoxy overcoat for imaging elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Protective epoxy overcoat for imaging elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2921395