Radiation imagery chemistry: process – composition – or product th – Imaged product – Multilayer
Reexamination Certificate
2000-10-30
2002-02-12
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaged product
Multilayer
C430S350000, C430S463000, C430S512000, C430S531000, C430S536000, C430S537000, C430S961000, C430S235000, C430S207000, C430S237000, C347S105000, C347S106000
Reexamination Certificate
active
06346353
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 an overcoat composition comprising a water-dispersible epoxy-functional latex is coated over an imaged element, including photographic elements and recording media. A method of forming a protective overcoat on an imaging element is also disclosed.
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 image formation. For an ink-jet recording element, an aqueous dye solution needs to be absorbed very quickly by the element or media to fix the dye image. Therefore, water-soluble polymers or materials that have affinity with water are proven to be the binders of choice for these imaging 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 damage 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. No. 4,092,173. 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. Another drawback is that the photographic materials need to be coated after the processing step. Thus, the processing equipment needs to be modified and the personnel running the processing operation need to be trained to apply the protective coating.
Alternatively lamination can be used to provide an imaged element with resistance to scratch, water, and stain resistance. Lamination involves placing a durable and/or adhesive protective layer coated on a suitable support to the image which is to be protected. The support of the protective coating may remain permanently adhered 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 the image after it is formed, several of which were mentioned above, adds 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.
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.
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 regarding to simultaneously satisfying the performance, environmental, and cost requirements. Also, in recent years, the use by the public of various printing and imaging technologies in the publishing industry as well as at home increasingly becomes more popular. It becomes 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 obtain a water-resistant imaged element with a protective overcoat with superior properties that avoids the problems and limitations of the prior art.
SUMMARY OF THE INVENTION
The present invention relates to a protective overcoat for an imaged element that provides water resistance, fingerprint resistance, and the like. This protective overcoat composition comprises epoxy-containing particles comprising at least 50% by dry weight 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 less than five microns. The overcoat composition further comprises, in the epoxy-containing particle, a polymer having acid groups. The protective overcoat composition also comprises a binder material for the epoxy-containing particles.
In one embodiment of the invention, the overcoat composition applied to the imaging element comp
O'Connor Kevin M.
Qiao Tiecheng A.
Wang Yongcai
Eastman Kodak Company
Konkol Chris P.
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