Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Antihalation or filter layer containing
Reexamination Certificate
2002-05-06
2004-03-23
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Antihalation or filter layer containing
C430S527000, C430S528000, C430S529000
Reexamination Certificate
active
06709808
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to multilayer imaging materials one or more electrically conductive, non-charging layers on either or both sides of a subbed or unsubbed support. This invention is directed to imaging sciences in general and photography, thermography, photothermography more specifically.
BACKGROUND OF THE INVENTION
Problems associated with the generation and discharge of electrostatic charge during the manufacture and use of photographic film and paper products have been recognized for many years by the photographic industry. The accumulation of static charge on film or paper surfaces can cause irregular static marking fog patterns in the emulsion layer. The presence of static charge also can lead to difficulties in support conveyance as well as the attraction of dust, which can result in, fog, desensitization, and other physical defects during emulsion coating. The discharge of accumulated charge during or after the application of the sensitized emulsion layer(s) also can produce irregular fog patterns or “static marks” in the emulsion layer. The severity of static-related problems has been exacerbated greatly by increases in the sensitivity of new emulsions, increases in coating machine speeds, and increases in post-coating drying efficiency.
The generation of electrostatic charge during the coating process results primarily from the tendency of webs to undergo triboelectric charging during winding and unwinding operations, during conveyance through the coating machines, and during finishing operations such as slitting and spooling.
Static charge can also be generated during the use of the final photographic film product. In an automatic camera, the winding of roll film out of and back into the film cassette, especially in a low relative humidity environment, can result in static charging and marking. Similarly, high-speed automated film processing equipment can produce static charging resulting in marking. Sheet films are especially subject to static charging during use in automated high-speed film cassette loaders (for example, radiographic and graphic arts films).
It is widely known and accepted that accumulated electrostatic charge can be dissipated effectively by incorporating one or more electrically conductive “antistatic” layers into the overall film structure. Antistatic layers can be applied to one or to both sides of the film support as subbing layers either underlying or on the side opposite to the sensitized emulsion layer. Alternatively, an antistatic layer can be applied as the bottom layers, intermediate layers, or outermost coated layer either over the emulsion layers (that is, as an overcoat) or on the side of the film support opposite to the emulsion layers (that is, as a back coat) or both.
A wide variety of electrically conductive materials can be incorporated in antistatic layers to produce a broad range of surface conductivities. Many of the traditional antistatic layers used for photographic applications employ materials that exhibit predominantly ionic conductivity. Antistatic layers containing simple inorganic salts, alkali metal salts of surfactants, alkali metal ion-stabilized colloidal metal oxide sols, ionic conductive polymers or polymeric electrolytes containing alkali metal salts and the like have been taught in the art. The electrical conductivities of such ionic conductors are typically strongly dependent on the temperature and relative humidity of the surrounding environment. At low relative humidity and low temperatures, the diffusion mobility of the charge carrying ions are greatly reduced and the bulk conductivity is substantially decreased. At high relative humidity, an exposed antistatic back coating can absorb water, swell, and soften. Especially in the case of roll films, this can result in a loss of adhesion between layers as well as physical transfer of portions of the back coating to the emulsion side of the film (viz. blocking). Also, many of the inorganic salts, polymeric electrolytes, and low molecular weight surface-active agents typically used in such antistatic layers are water soluble and can be leached out during film processing, resulting in a loss of antistatic function.
One of the numerous methods proposed in the art for increasing the electrical conductivity of the surface of photographic light-sensitive materials in order to dissipate accumulated electrostatic charge involves the incorporation of at least one of a wide variety of surfactants or coating aids in the outermost (surface) protective layer overlying the emulsion layer(s). A wide variety of ionic-type surfactants have been evaluated as antistatic agents including anionic, cationic, and betaine-based surfactants. The use of nonionic surfactants having at least one polyoxyethylene group as antistatic agents has been disclosed. Further, surface protective layers containing nonionic surfactants having at least two polyoxyethylene groups have been disclosed.
In order to provide improved performance, the incorporation of an anionic surfactant having at least one polyoxyethylene group in combination with a nonionic surfactant having at least one polyoxyethylene group in the surface layer was disclosed in U.S. Pat. No. 4,649,102. A further improvement in antistatic performance by incorporating a fluorine-containing ionic surfactant having a polyoxyethylene group into a surface layer containing either a nonionic surfactant having at least one polyoxyethylene group or a combination of nonionic and anionic surfactants having at least one polyoxyethylene group was disclosed in U.S. Pat. Nos. 4,510,233 and 4,649,102. Additionally, surface or backing layers comprising a combination of specific cationic and anionic surfactants having at least one polyoxyethylene group in each which form a water-soluble or dispersible complex with a hydrophilic colloid binder are disclosed in European Patent Publication 650,088 and British Patent Publication 2,299,680.
Surface layers containing either non-ionic or anionic surfactants having polyoxyethylene groups often demonstrate specificity in their antistatic performance such that good performance can be obtained against specific supports and photographic emulsion layers but poor performance results when they are used with others. Surface layers containing fluorine-containing ionic surfactants generally exhibit negatively charged triboelectrification when brought into contact with various materials. Such fluorine-containing ionic surfactants exhibit variability in triboelectric charging properties after extended storage, especially after storage at high relative humidity.
However, it is possible to reduce triboelectric charging from contact with specific materials by incorporating into a surface layer other surfactants which exhibit positively charged triboelectrification against these specific materials. The dependence of the triboelectrification properties of a surface layer on those specific materials with which it is brought into contact can be somewhat reduced by adding a large amount of fluorine-containing nonionic surfactants.
However, the use of a large amount of said fluorine-containing surfactants results in decreased emulsion sensitivity, increased tendency for blocking, and increased dye staining during processing. Thus, it is extremely difficult to minimize the level of triboelectric charging against all those materials with which an imaging element may come to contact without seriously degrading other requisite performance characteristics of the imaging element.
The inclusion in a surface or backing layer of a combination of three kinds of surfactants, comprising at least one fluorine-containing nonionic surfactant, and at least one fluorine-containing ionic surfactant, and a fluorine-free nonionic surfactant has been disclosed to reduce triboelectric charging, prevent dye staining on processing, maintain antistatic properties on storage, and preserve sensitometric properties of the photosensitive emulsion layer. The level of triboelectric charging of surface or backing layers contai
Lelental Mark
Mosehauer Gary M.
Owers Roger J.
Wakley James L.
Eastman Kodak Company
Schilling Richard L.
Tucker J. Lanny
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