Radiation imagery chemistry: process – composition – or product th – Post imaging processing – Developing
Reexamination Certificate
2000-09-29
2002-05-28
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Post imaging processing
Developing
Reexamination Certificate
active
06395459
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, a curable overcoat composition is applied to an imaged element that contains a curing agent incorporated into a top layer of the imaged element, resulting in a cured water-resistant and/or stain resistant overcoat. The invention can be used to protect photographic elements and recording media.
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. However, due to this same property, imaging elements with exposed gelatin-containing materials, no matter if they are formed on transparent or reflective media, have to be handled with extreme care so as not to be in contact with any aqueous solutions that may damage the images. Accidental spillage of common household solutions such as coffee, punch, or even plain water can damage imaging 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 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. 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. The application of UV-polymerizable monomers and oligomers on processed image followed by radiation exposure to form crosslinked protective layer is described in U.S. Pat. Nos. 4,092,173, 4,171,979, 4,333,998 and 4,426,431. Aqueous based materials to obtain a spill resistant protective overcoat have been disclosed in which aqueous dispersed particles when coated and dried coalesce into a uniform coating. See, for example, U.S. Pat. No. 5,376,434 to Ogawa et al. and U.S. Pat. No. 6,087,051 to Shoji et al.
In addition to a uniform coating, it may be advantageous to develop a level of crosslinking in an overcoat in order to build spill resistance and durability. One method for obtaining crosslinking is the use of molecules containing two or more reactive moieties (i.e., multifunctional molecules) that can be cured when exposed to high temperatures or actinic radiation. Various patents describe the use of actinic radiation to obtain a crosslinkable overcoat for photographic packages. For example, U.S. Pat. No. 4,092,173 to Novak et al. discloses an overcoat technology using UV curable or actinic radiation for curing. This patent describes an acrylated urethane polyfunctional acrylate ester which is applied to photographic elements for scratch resistance. U.S. Pat. No. 4,171,979 also to Novak et al. discloses an improvement upon U.S. Pat. No. 4,092,173 and includes repair of surface defects. U.S. Pat. No. 4,333,998 to Leszyk discloses an improvement upon U.S. Pat. No. 4,092,173 by the addition of a siloxycarbinol to the radiation curable composition.
U.S. Pat. No. 4,426,431 to Harasta et al. discloses a photocurable coating for restorative or protective treatment that uses a composition comprising a polymerizable epoxide, a polymerizable acrylic compound, catalyst, and a polymerizable organofunctional silane. The coating appears to involve a standard cationically initiated epoxy reaction. Other patents also disclose cationically initiated epoxy type systems. For example, EP 0 484 083 (1991) discloses triglycidyl ethers of trimethylol alkanes initiated with onium salts. U.S. Pat. Nos. 4,619,949 and 4,587,169 to Kistner disclose the use of an epoxy terminated silane and an aliphatic monomer epoxy resin, cationically initiated with an onium salt.
The UV-curable coatings described in the above-mentioned U.S. Pat. Nos. 4,619,949, U.S. Pat. No. 4,587,169, and in EP 0 484 083 (1991), where an epoxy based liquid overcoat containing a photoinitiator is coated to the surface of a photographic image, are neat monomer systems that are 100% monomer and photoinitiator. Prior to cure, they are liquids that are difficult to handle and may create a health hazard if handled incorrectly.
U.S. Pat. No. 4,107,013 to McGiniss et al. describes a paint comprising a high molecular weight aqueous latex solution combined with a low molecular weight photocrosslinkable polymer. This composition has the advantage that heating of the coating to provide flow-out or leveling is eliminated. The low molecular weight crosslinker further provides flexibility and substrate adhesion while maintaining corrosion and wear resistance film characteristics. This patent does not disclose the use of such a coating for an imaging element, but is directed to improving the properties of a paint.
U.S. Pat. No. 4,186,069 to Muzyczko et al. discloses a latex solution with an incorporated photopolymerizable component. The system is described as a three-phase system prior to coating, including an aqueous phase, a latex phase, and a light-sensitive polymer phase. Upon coating, this system becomes a two-phase system consisting of a latex phase and a light-sensitive polymer phase. These systems are aimed at water developable lithographic printing plates.
It would be advantageous to have an overcoat composition that would provide protection for a photographic element, which overcoat could be applied to the imaged element quickly and economically. It is difficult, however, to coat a photographic element, because a coating composition that has good coating properties may not have good protective properties for an imaged element. It would be desirable to obtain a protective overcoat with the desired protective properties in the final product but which, at the same time, can be applied efficiently and economically in a photoprocessing setting, for example, as an adjunct to a conventional minilab operation. Not only for ease of handling, but for uniform coating properties, it would also be desirable for a curable coating composition to cure rapidly after it is applied to the substrate to be coated, but at the same time, not to cure prematurely, either during storage or before the film-forming has been completed. It would be desirable that any process for coating photographs or digital prints be robust in nature, not adversely sensitive to variations in the operating conditions.
SUMMARY OF THE INVENTION
The present invention is directed to a method of processing an imaged element to provide a cured overcoat that can protect the element from aqueous spills, fingerprints, and the like. It has been found that by the curing of a protective overcoats on an imaged element, improved performance is obtained with respect to durability, fingerprint resistance, and scratch resistance. The present invention generally involves two parts: (1) an imaged element that has incorporated in a top layer thereof a curing agent that will initiate crosslinking or that will initiate polymerization of a multifunctional monomer, and (2) an overcoat composition that when applied to the imaged element (in which the curing agent is incorporated) will crosslink, resulting in a superior spill resistant protective overcoat.
In one embodiment of the present invention, the imaged element is a photographic print comprising a support and at least one gelatin-based imaged layer. In a further embodiment, the protective overcoat overlying the gelatin-based imaged layer is the made from a composition compri
Boettcher John W.
Flood Elmer C.
Taylor Jeffrey F.
Whitesides Thomas H.
Yau Hwei-Ling
Eastman Kodak Company
Konkol Chris P.
Le Hoa Van
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