Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified backing or protective layer containing
Reexamination Certificate
1999-12-27
2001-03-06
Schilling, Richard L. (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified backing or protective layer containing
C430S529000, C430S531000, C430S536000
Reexamination Certificate
active
06197486
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to imaging elements, such as photographic, electrostatographic and thermal imaging elements, and in particular to imaging elements comprising a support, an image-forming layer, and an electrically-conductive layer used in reflective photographic media. More specifically, this invention relates to electrically-conductive layers comprising electrically-conductive polymers which can be applied during film extrusion and are integral to the reflective photographic support, and to the use of such electrically-conductive layers in imaging elements for such purposes as providing protection against the generation of static electrical charges.
BACKGROUND OF THE INVENTION
The problem of controlling static charge is well known in the field of photography. The accumulation of charge on film or paper surfaces leads to the attraction of dirt, which can produce physical defects. The discharge of accumulated charge during or after the application of the sensitized emulsion layer(s) can produce irregular fog patterns or “static marks” in the emulsion. The static problems have been aggravated by increase in the sensitivity of new emulsions, increase in coating machine speeds, and increase in post-coating drying efficiency. The charge generated during the coating process may accumulate during winding and unwinding operations, during transport through the coating machines, and during finishing operations such as slitting and spooling.
It is generally known that electrostatic charge can be dissipated effectively by incorporating one or more electrically-conductive “antistatic” layers into the support structure. Antistatic layers can be applied to one or to both sides of the support as subbing layers either beneath or on the side opposite to the light-sensitive silver halide emulsion layers. An antistatic layer can alternatively be applied as an external layer either over the emulsion layers or on the side of the support opposite to the emulsion layers or both. For some applications, the antistatic agent can be incorporated into the emulsion layers. Alternatively, the antistatic agent can be directly incorporated into the support itself.
A wide variety of electrically-conductive materials can be incorporated into antistatic layers to produce a wide range of conductivities. These can be divided into two broad groups: (i) ionic conductors and (ii) electronic conductors. In ionic conductors charge is transferred by the bulk diffusion of charged species through an electrolyte. Here the resistivity of the antistatic layer is dependent on temperature and humidity. Antistatic layers containing simple inorganic salts, alkali metal salts of surfactants, ionic conductive polymers, polymeric electrolytes containing alkali metal salts, and colloidal metal oxide sols (stabilized by metal salts), described previously in patent literature, fall in this category. However, many of the inorganic salts, polymeric electrolytes, and low molecular weight surfactants used are water-soluble and are leached out of the antistatic layers during processing, resulting in a loss of antistatic function. The conductivity of antistatic layers employing an electronic conductor depends on electronic mobility rather than ionic mobility and is independent of humidity. Antistatic layers which contain conjugated polymers, semiconductive metal halide salts, semiconductive metal oxide particles, etc., have been described previously. However, these antistatic layers typically contain a high volume percentage of electronically conducting materials which are often expensive and impart unfavorable physical characteristics, such as color, increased brittleness, and poor adhesion to the antistatic layer.
Besides antistatic properties, an auxiliary layer in a photographic element may be required to fulfill additional criteria depending on the application. For example, for resin-coated photographic paper, the antistatic layer if present as an external backing layer should be able to receive prints (e.g., bar codes or other indicia containing useful information) typically administered by dot matrix printers and to retain these prints or markings as the paper undergoes processing. Most colloidal silica based antistatic backings without a polymeric binder provide poor post-processing backmark retention qualities for photographic paper.
In general, poor adhesion of the antistatic coating onto the resin-coated paper support may be responsible for a number of problems during manufacturing, sensitizing, and photofinishing. Poor adhesion or cohesion of the antistatic layer can lead to unacceptable dusting and track-off. A discontinuous antistatic layer, resulting from dusting, flaking, or other causes, may exhibit poor conductivity and may not provide necessary static protection. It can also allow leaching of calcium stearate from the paper support into the processing tanks causing buildup of stearate sludge. Flakes of the antistatic backing in the processing solution can form soft tar-like species which, even in extremely small amounts, can redeposit as smudges on drier rollers eventually transferring to image areas of the photographic paper, creating unacceptable defects.
Although the prior art is replete with patents disclosing various antistatic backings for photographic paper (for example, U.S. Pat. Nos. 3,671,248; 4,547,445; 5,045,394; 5,156,707; 5,221,555; 5,232,824; 5,244,728; 5,318,886; 5,360,707; 5,405,907 and 5,466,536), not all of the aforesaid issues are fully addressed by these inventions. A vast majority of the prior art involves coatings of antistatic layers from aqueous or organic solvent based coating compositions. This technique, however, necessitates an effective elimination of the solvent which may not be trivial especially under faster drying conditions, as dictated by efficiency. An improper drying will invariably cause coating defects, generating waste or inferior performance.
PROBLEM TO BE SOLVED BY THE INVENTION
There is a need for antistatic layers that are an integral part the photographic support and do not require an additional step for antistatic coating after the support formation.
SUMMARY OF THE INVENTION
It is an object of the invention to provide improved antistatic protection to a reflection photographic imaging element.
It is another object of the invention to apply an antistatic layer is a less costly manufacturing process.
It is a further object of the invention to have an antistatic layer that is transparent or translucent and is able to survive photographic processing.
These and other objects of the invention are accomplished by reflection photographic imaging element comprising at least one silver halide layer, a support comprising at least one extruded layer comprising an antistatic material. Said antistaic layer is formed integrally with the polymeric sheet by the (co)-extrusion method during the support manufacturing step.
ADVANTAGEOUS EFFECT OF THE INVENTION
The invention provides a photographic support with an integral antistatic layer that does not require an additional antistatic coating step after base formation.
DETAILED DESCRIPTION OF THE INVENTION
The invention has numerous advantages over prior practices in the art. The invention provides photographic materials that have good antistatic properties and do not require a separate step for antistatic coating. Further, the imaging members of the invention are much less likely to lose antistatic materials during processing and handling of the imaging layers. The imaging members of the invention having integral antistatic layers do not require a separate step for coating antistatic materials which would require removal of solvents and thereby increase manufacturing costs. As the imaging material of the invention is not aftercoated with the antistatic material, there is no need for the drying step required in the prior art processes. There is a cost advantage, as there is one less coating and drying step required in image member formation. These and other advantages will be apparent from the detailed de
Greener Jehuda
Laney Thomas M.
Majumdar Debasis
Eastman Kodak Company
Leipold Paul A.
Schilling Richard L.
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