Radiation imagery chemistry: process – composition – or product th – Imaged product – Multilayer
Reexamination Certificate
2000-09-25
2002-03-05
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaged product
Multilayer
C430S432000, C430S532000, C430S536000, C430S961000, C347S105000
Reexamination Certificate
active
06352805
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, an overcoat composition comprising a water-dispersible latex, a photopolymerizable monomer, and a photoinitiator is coated over an imaged element, including 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. 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. 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. 5 4,092,173, 4,171,979, 4,333,998 and 4,426,431. A drawback for both the solvent coating method and for the radiation cure method is the health and environmental concern of those chemicals or radiation to the coating operator.
There have been previous invention reports and patents that have described overcoat technology that would produce an overcoat for photographic systems. 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 would be advantageous to develop a level of crosslinking to build spill resistance and durability. One method for obtaining crosslinking is the use of molecules containing more than two reactive moieties (or 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 or 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. 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. 5 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. No. 4619949, U.S. Pat. No. 4587169, 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 mention coatings for an imaging element, but is focused on improving paint properties. Furthermore, McGiniss et al. does not describe the use of a loaded latex containing a photopolymerizable component.
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 3 phase system prior to coating with an aqueous phase, a latex phase, and a light sensitive polymer phase. Upon coating, this system becomes a 2 phase system consisting of a latex phase and a light sensitive polymer phase. These systems are aimed at water developable lithographic printing plates.
A problem with UV-curing, as practiced in the prior art, is obtaining the desired combination of properties in the final coating and, at the same time, being able to commercially implement the application of the coating economically and efficiently. In the imaging field, high clarity, high gloss coatings that are water-resistant, oil resistant, and scratch resistant are desired. The coatings may need to be applied in a minilab setting, where worker safety and convenience are important.
SUMMARY OF THE INVENTION
The present invention is directed to a protective overcoat for an imaged element that provides water resistance, fingerprint resistance, and the like. It has been found that by UV-curing of a protective overcoat on an imaged element, improved performance is obtained with respect to durability, fingerprint resistance, and scratch resistance. In one embodiment of the present invention, a photographic print comprises a support, at least one gelatin-based imaged layer, and overlying the gelatin-based imaged layer, a protective overcoat that is the made from a composition comprising an aqueous dispersible latex and a photopolymerizable component system comprising a mixture of at least two components, a photoinitiator and a crosslinkable multifunctional monomer or macromonomer. The component system may include monofunctional monomers. The term “multifunctional monomer” is herein defined as a monomer having a plurality of ethylenically unsaturated sites for polymerization or copolymerization. This photopolymerizable component system is preferably loaded into the latex phase. More specifically, the photopolymerizable components are designed to be sufficiently hydrophobic that the photopolymerizable components absorb into the latex particles, yielding a monomer/initiator swollen particle. Alternatively, the photopolymerizable components may be water soluble and part of the aqueous phase. Th
Chen Tien-teh
Flood Elmer C.
O'Connor Kevin M.
Taylor Jeffrey F.
Yau Hwei-Ling
Eastman Kodak Company
Konkol Chris P.
Schilling Richard L.
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