Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Silicon dioxide – silicic acid – orthosilicate – or...
Reexamination Certificate
2000-05-11
2003-06-03
Johnson, Jerry D. (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Silicon dioxide, silicic acid, orthosilicate, or...
C508S154000, C508S179000, C508S243000, C508S264000, C508S266000, C508S267000, C508S269000, C508S283000
Reexamination Certificate
active
06573222
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to imaging and in particular to a novel imaging element that is especially useful in photographic film and paper. More specifically, this invention relates to a photographic element having at least one light-sensitive layer and a protective topcoat, the topcoat being farthest from the support and containing lubricant droplets and a water soluble polymer containing heterocyclic aromatic nitrogen groups.
BACKGROUND OF THE INVENTION
Various lubricants have been employed in photographic film and papers products, especially in the outermost layer or layers of the element.
In U.S. Pat. No. 5,529,891, droplets of lubricant having a size relationship with respect to the thickness of the layer of a photographic element in which the droplets reside are disclosed. It is desired that the lubricating droplets have a narrow particle size distribution.
Because of the nature of liquid lubricant droplets, it is extremely difficult to obtain droplets that are stable over any length of time. Thus, it is readily apparent that it is difficult to provide uniformly sized, stable lubricant droplets. U.S. Pat. No. 5,541,048 describes a process for making stable lubricant droplets capable of being applied from a coating composition to form layers of uniformly sized lubricant droplets in a binder and photographic elements having at least one layer containing uniformly sized and dispersed lubricant droplets. Combining these lubricant droplets with a hydrophilic binder such as gelatin is not straightforward and requires a surfactant to prevent destabilization or aggregation of the lubricant droplets. Additionally, in making the lubricant droplets, a solvent, either volatile or permanent is necessary in order to increase the surface energy of the droplet and facilitate the partitioning of the particulate suspension stabilizing agent onto the surface of the lubricant droplets from the water medium.
It is toward the objective of overcoming the aforesaid problems and limitation of the prior art that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention is an imaging element which includes a support, at least one imaging layer superposed on the support and a protective topcoat superposed farthest from the support. The topcoat includes a binder and lubricant droplets. The lubricant droplets are composed of a lubricant and a water soluble polymer containing heterocyclic aromatic nitrogen groups wherein the droplets are surrounded by a particulate stabilizer. The present invention is also directed to the lubricant droplets.
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. Such elements include, for example, photographic, electrophotographic, electrostatographic, photothermographic, migration, electrothermographic, ink-jet receiving paper, dielectric recording and thermal-dye-transfer imaging elements. Photographic elements can comprise various polymeric films, papers, glass, and the like. The thickness of the support is not critical. Support thickness of 2 to 15 mils (0.05 to 0.40 millimeters) can be used. The supports typically employ an undercoat or subbing layer well known in the art or are treated with a corona discharge to improve adhesion.
In accordance with this invention a novel imaging element that is especially useful in photographic film and paper includes a photographic element having at least one light-sensitive layer and a protective topcoat, the topcoat being farthest from the support and containing lubricant droplets and a water soluble polymer containing heterocyclic aromatic nitrogen groups.
The water soluble polymer containing heterocyclic aromatic nitrogen groups is very effective in enhancing the adsorption of the particulate suspension stabilizing agent at the interface between the low surface energy lubricant droplet and water. This polymer aids in keeping the particles well dispersed in water thereby prolonging the shelf life of an aqueous colloidal dispersion of the oil droplets. Additionally, the water soluble pyridine containing polymer enhances the dispersibility of the droplets in hydrophilic colloids such as gelatin without the need for an added surfactant.
In a preferred embodiment of the present invention, the lubricant layer utilizes silicone oil droplets particularly DC200 (polydimethyl siloxane) made by Dow Coming as the lubricant. The preparation of such size stable lubricant droplets involves forming a discontinuous phase of lubricant droplets in a continuous aqueous phase containing a particulate suspension stabilizing agent. The lubricant droplets are reduced in size and prevented from coalescing by action of the particulate suspension stabilizing agent as described in U.S. Pat. No. 5,541048. In the preparation of photographic elements containing a layer having therein lubricant droplets, it has been found that the size of the lubricant droplets and the uniformity of the droplets size is an important parameter with regard to the quality of the photographic image, and the scratch resistance of the photographic element when it comes in contact with other parts of the apparatus in which it is employed, such as, cameras, photo processes apparatus, and the like. A particular embodiment of this is set forth in previously mentioned U.S. Pat. No. 5,529,891.
The lubricant droplets as described herein are prepared by forming a discontinuous phase of lubricant droplets in a continuous aqueous phase containing a particulate suspension stabilizing agent, reducing the size of the lubricant droplets and limiting the coalescence of the droplets by the action of the particulate suspension stabilizing agent on the surface of the droplets.
In one embodiment the particular lubricant employed is mixed with either a volatile solvent or with a permanent solvent and then dispersed in an aqueous medium containing the particulate suspension stabilizing agent and the promoter, the purpose of which is to drive the particulate suspension stabilizing agent to the interface between the lubricant droplet and the water medium. The dispersion of lubricant droplets in the aqueous medium is then vigorously mixed by any suitable device including high speed agitation, ultrasonic devices, homogenizers, and the like in order to reduce the particle size of the lubricant droplets to less than that ultimately desired. The presence of the particulate suspension stabilizer then controls the level of coalescence that takes place until an equilibrium is reached and the particle size does not grow any farther. The primary role of the solvents is to lower the viscosity of the oil phase if necessary and sometimes to enhance the surface energy of the oil droplets and promote adsorption of the particulate stabilizer at the interface. In another embodiment where no solvent is used, the viscosity of the oil phase is lowered by raising the temperature of the system. Any of these methods give narrow particle size distributions with the mean particle size of the droplets being controlled by the amount of the particulate suspension stabilizing agent employed in the preparation of the dispersion. In the preparation including the volatile solvent, the solvent can then be driven off by raising the temperature to above the volatilization temperature of the solvent. The droplets are further employed in the preparation of a coating composition for use in the preparation of an imaging element. In the case using a permanent solvent and where no solvent is used, the droplets including the permanent solvent are employed directly in the preparation of the coating composition.
In order to provide suitable formulations for applying a layer containing the lubricant droplets in accordance with this invention for use in a photographic element, the dispersions prepared by the methods described above, are combined with a hydrophilic colloid, gelatin being the preferred material.
There is no limitation on the types of lubricants for the practice of
Nair Mridula
Osburn Tamara K.
Sorriero Louis J.
Eastman Kodak Company
Johnson Jerry D.
Konkol Chris P.
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