Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
1998-12-28
2001-01-23
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, C430S531000, C430S533000, C430S536000, C430S961000, C430S950000
Reexamination Certificate
active
06177239
ABSTRACT:
FIELD OF THE INVENTION
This invention is related to an imaging element having a lubricant layer including 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 recording and thermal-dye-transfer imaging elements.
Layers of imaging elements other than the image-forming layer are commonly referred to 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 silicone fluid as described in U.S. Pat. No. 3,489,567, and a wax esters of high fatty acids or high fatty alcohols in U.S. Pat. No. 3,121,060. However, problems are encountered in the use of these lubricants. For example, when silicone is used as a lubricant for a backing layer, it may move to the surface of the support where an image element is to be coated. This will give an adverse effect (e.g. wetting) on the subsequent coating processes. They may also not survive processing so that the advantage of low surface friction is lost for the post-processed products. In addition, 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 enviromental and health standpoint. It is also 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 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 microns. 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 expenses. 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.
Therefore, a foremost objective of the present invention is to provide an imaging element with a new lubricant layer composition which survives photographic material processing, does not transfer to the surface of the support to which the imaging layer to be coated, and can be applied from a low hazard organic solvent or solvent mixture.
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 is formed from a non-aqueous coating composition composed of a composite wax particle having a wax phase and a non-crosslinked polymer phase. The wax phase includes a wax having a melting point of greater than 30° C., the wax comprising greater than 80% by weight of the wax phase. The at least one layer has a dry coating weight of from 1 to 300 mg/m
2
.
DETAILED DESCRIPTION OF THE INVENTION
In accordance with the presence invention, the lubricant layer is formed from a nonaqueous coating composition and contains more than 80% of a composite wax particle having a wax phase and a non-crosslinked polymer phase. The wax phase comprises greater than 80% by weight of a wax having a melting point of greater than 30° C. The total coating weight in the lubricant layer is in the range of from 1 to 300 mg/m
2
and preferably from 5 to 150 mg/m
2
. In principle, the upper value of the composite wax particle is limited by both the physical appearances and friction values of the lubricant layer. For example, if the coverage is too high, a hazy looking surface will appear, which therefore can have an effect on the sensitometric properties of the imaging element. The lower limiting value is set by the requirement on the surface friction value of the lubricant layer, which is determined by both manufacturing processes and applications of the imaging element.
A preferred imaging element according to the present invention comprises one or more imaging layers on one side of the support and the lubricant layer present on the other side of the support as an outermost backing layer, or as an outermost layer coated on the top of an abrasion resistance backing layer, or as an outermost layer coated on the top of an antistatic layer, or as an outermost layer coated on an magnetic recording layer. The lubricant layer can contain additives such as coating aids, charge control surfactants, matting agents, and crosslinkers.
According to a first embodiment said composite wax particles are coated from a solvent on a support surface which is unsubbed or subbed with an adhesion promotion layer (primer layer). The unsubbed support surface can be pre-modified with treatment such as, for example, corona discharge, plasma, solvent itching, and the like. The support surface can also 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.
According to a second embodiment the composite wax particles are coated from a solvent on a support which employs an abrasion resistance backing layer that comprises, for example, an acrylic polymer, a cellulose derivative, a polyurethane, a mixture of film-forming and non-film forming polymer particles, a sol-gel material, and the like. Such abrasion resistance layer composition has been described in, f
Chen Janglin
Schwark Dwight W.
Wang Yongcai
Eastman Kodak Company
Ruoff Carl F.
Schilling Richard L.
Wells Doreen M.
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