Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
1998-12-28
2001-02-13
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Antihalation or filter layer containing
C430S510000, C430S517000, C430S523000, C430S527000, C430S529000, C430S530000, C430S531000, C430S533000, C430S536000, C430S950000, C430S961000
Reexamination Certificate
active
06187521
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to imaging elements such as, for example, photographic elements and in particular to imaging elements comprising a support, an image-forming layer and one or more auxiliary layers. More specifically, this invention relates to such imaging elements that have at least one layer comprising a composite wax particle.
BACKGROUND OF THE INVENTION
The imaging elements to which this invention relates can be of many different types depending on the particular use for which they are intended. Such elements include, for example, photographic, electrophotographic, electrostatographic, photothermographic, migration, electrothermographic, dielectric recording, inkjet ink image recording and thermal-dye-transfer imaging elements.
Layers of imaging elements other than the image-forming layer are commonly referred to as auxiliary layers. There are many different types of auxiliary layers such as, for example, subbing layers, backing layers, interlayers, overcoat layers, receiving layers, stripping layers, antistatic layers, transparent magnetic layers, and the like.
Support materials for an imaging element often employ auxiliary layers comprising glassy, hydrophobic polymers such as polyacrylates, polymethacrylates, polystyrenes, or cellulose esters, for example. One typical application for such an auxiliary layer is as a backing layer to provide resistance to abrasion, scratching, blocking, and ferrotyping. Such backing layers may be applied directly onto the support material, applied onto a priming or “subbing” layer, or applied as an overcoat for an underlying layer such as an antistatic layer, transparent magnetic layer, or the like. For example, U.S. Pat. No. 4,203,769 describes a vanadium pentoxide-containing antistatic layer that is overcoated with a cellulosic layer applied from an organic solvent. U.S. Pat. Nos. 4,612,279 and 4,735,976 describe organic solvent-applied layers comprising a blend of cellulose nitrate and a copolymer containing acrylic acid or methacrylic acid that serve as overcoats for antistatic layers.
Frequently, when the auxiliary layer serves as the outermost layer, as is the case for a backing layer, it is desirable for this layer to have a low coefficient of friction (COF) to provide proper conveyance properties and to protect the imaging element from mechanical damage during the manufacturing process or customer use. It is known to protect imaging elements against mechanical damage by coating them with a layer comprising a lubricant such as a wax. However, it has proven difficult to provide a single layer applied from organic medium that comprises both an abrasion-resistant polymer and a lubricant since it is difficult to find a coating medium that dissolves both the polymer and the lubricant and is at the same time attractive from an environmental and health standpoint. In addition, it is difficult to form a stable dispersion of a lubricant such as a wax in an organic medium that may be added to a coating composition containing a dissolved, abrasion-resistant polymer. Therefore, in order to form a backing layer which can be applied from liquid organic medium that is both abrasion-resistant and has a low coefficient of friction one often applies two separate layers; a first layer which is comprised of an abrasion-resistant polymer and then a second layer which is comprised of a lubricant such as a wax. The need to apply these two separate layers increases both manufacturing complexity and cost.
U.S. Pat. No. 4,766,059 describes a method of making solid spherical beads having a mean size ranging form 0.5 to about 20 &mgr;m. The polymer beads contain a polymeric resinous material and a water insoluble wax. The process of making such solid beads involves the use of water miscible or immiscible low boiling solvent to dissolve both polymeric materials and wax, and subsequently removal of the solvent or solvent mixture by evaporation. This requires large processing equipment and lengthy processing time, which increases the cost of such material. U.S. Pat. No. 5,695,919 describes a lubricant impregnated core/shell polymer particle, the polymer particle comprising a core portion which is insoluble in the organic medium and a shell portion which has an affinity for both the core portion and the organic medium.
The objective of this invention is to provide an imaging element with a wax particle composition which, when used in a surface layer, for example, provides the imaging element with superior surface characteristics.
SUMMARY OF THE INVENTION
The present invention is an imaging element which includes a support, an image forming layer superposed on the support; and at least one layer superposed on the support. The at least one layer superposed on the support is formed from a non-aqueous coating composition of a composite wax particle composed of a wax phase and a non-crosslinked polymer phase and an organic solvent. The wax phase includes a wax having a melting point of greater than 30° C. The wax comprises greater than 80% by weight of the wax phase. The wax phase to non-crosslinked polymer phase ratio is greater than 30/70 and less than 90/10.
DETAILED DESCRIPTION OF THE INVENTION
The imaging elements of this invention can be of many different types depending on the particular use for which they are intended. Details with respect to the composition and function of a wide variety of different imaging elements are provided in U.S. Pat. No. 5,300,676 and references described therein.
Photographic elements can comprise various polymeric films, papers, glass, and the like, but both acetate and polyester supports well known in the art are preferred. The thickness of the support is not critical. Support thickness of 2 to 10 mil (0.06 to 0.30 millimeters) can be used. The supports typically employ an undercoat or subbing layer well known in the art that comprises, for example, for polyester support a vinylidene chloride/methyl acrylate/itaconic acid terpolymer or vinylidene chloride/acrylonitrile/acrylic acid terpolymer.
In accordance with the invention, the imaging elements have at least one layer formed from a non-aqueous coating composition comprising a composite wax particle having a wax phase and a non-crosslinked polymer phase. The wax phase is composed of greater than 90% by weight of a wax having a melting point of greater than 30° C. The wax phase to non-crosslinked polymer phase ratio is greater than 30/70 and less than 90/10. The wax phase is preferably insoluble in the solvent medium.
Wax useful for the practice of the invention has been described, for example, in references such as “The Chemistry and Technology of Waxes”, A. H. Warth, 2
nd
Ed., Reinhold Publishing Corporation, New York, N.Y. 1956, and “Plastics Additives and Modifiers Handbook”, Chapter 54-59, J. Ederibaum (Ed.), Van Nostrand Reinhold, New York, N.Y. 1992. Suitable waxes include hydrocarbon and/or ester-containing waxes, e. g. animal waxes such as beewax, plant waxes such as carnauba wax, paraffin waxes, microcrystalline waxes, Fischer-Torpsch waxes, polyethylene waxes, polypropylene waxes, and a mixture thereof.
The composite wax particle of the present invention is preferably prepared by polymerizing a vinyl monomer or a monomer mixture in the presence of pre-formed aqueous wax particles. Pre-formed aqueous wax dispersion (or emulsion) is primarily composed of wax particles, dispersants/surfactants, and water. The dispersants can be nonionic, anionic, and cationic, and can be polymeric and are used at levels as high as 20% of the wax. Wax particles can be formed by various methods known in the art. For example, they can be prepared by pulverizing and classifying dry waxes or by spray drying of a solution containing waxes followed by redispersing the resultant particles in water using a dispersant; they can be prepared by a suspension technique which consists of dissolving a wax in, for example, a water immiscible solvent, dispersing the solution as fine liquid droplets in aqueous solution, and removing the solvent by evaporation or othe
Bello James L.
Chen Janglin
Schwark Dwight W.
Wang Yongcai
Eastman Kodak Company
Schilling Richard L.
Wells Doreen M.
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