Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
1994-01-18
2001-01-09
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of polyester
C428S532000, C428S922000
Reexamination Certificate
active
06171707
ABSTRACT:
The present invention relates to a method for reducing the chargeability of polymeric films, particularly polymeric film base used with photographic layers and photographic elements, to photographic layers and photographic elements obtained with such a method.
A photographic material generally consists of a base, at least one layer of a silver halide emulsion dispersed in a hydrophilic colloidal binder and, possibly, of at least one protective layer for such an emulsion, essentially consisting of a hydrophilic colloidal binder. Such a protective layer can be found either outside or inside such a photographic material (in this last case, for instance in color photographic materials, it is called “interlayer”). It is also known that a photographic material may include sub-layers, antihalation layers and other auxiliary layers adjacent or not the emulsion layers. A photographic material suitable for radiography particularly consists of a base, at least two emulsion layers each coated on one surface of said base and at least two protective layers for said emulsion layers. Such a material may also contain two sub-layers coated between the emulsion layers and the base.
It is further known that it is desirable to produce photographic layers, i.e., emulsion layers and auxiliary layers (such as for instance protective layers, interlayers, sublayers and antihalation layers) exhibiting a reduced static chargeability. During preparation, packaging or use, such layers are prone to stresses which may cause electrostatic charges to be formed, which by discharging produce undesired sensitizations in light-sensitive emulsions. Particularly, a radiographic material should be usable in angiographic tables (AOT) and in rapid machines wherein the film is conveyed at a high speed by means of rollers which exert thereon a strong pressure and friction action.
In such use, strong electrostatic charges are formed at the surface of contact between the protective layer and the rollers, thus giving rise to undesired sensitizations. Such sensitizations are equivalent to undesired exposures and after the processing sequence the photographic element will have variedly shaped specks which can be found above all along the film sides where the contact rollers/protective layers occurs.
In addition to a reduced chargeability, radiographic materials suitable for AOT must exhibit a rather high slipperiness index which reduces the dangers of the apparatus jamming. In some cases, indeed, the slipperiness index can be related to the static chargeability itself.
The chargeability of the layers is generally due to the fact that the layers essentially consist of gelatin or of another hydrophilic colloidal binder equivalent to gelatin which exhibits a low work function, i.e., a positive type chargeability. Such a chargeability is generally modified by the presence of surfactants which induce a positive or a negative type chargeability into the layers according to their nature. “Non-fluorinated” anionic surfactants of the type known to those skilled in the art generally induce a positive type chargeability into the layers. Fluorinated anionic, non-ionic N-oxide or betaine surfactants induce a negative type chargeability into the same layers. Betaine and/or N-oxide non-fluorinated surfactants in combination with non-fluorinated anionic surfactants do not substantially improve the static characteristics of the photographic layers, while on the contrary they improve slipperiness characteristics. Fluorinated surfactants in combination with anionic non-fluorinated surfactants improve the static characteristics of the photographic layers only at a certain range of relative humidity and leave slipperiness characteristics unaltered.
Fluorinated compounds, fluorinated polymers and mixtures of those materials have been used for antistatic protection in polymer films and particularly in photographic media for many years. U.S. Pat. No. 3,884,699 shows the use of combinations of fluorinated anionic surfactants and non-fluorinated betaines and/or N-oxide surfactants in coated layers to reduce static charging in photographic film. U.S. Pat. No. 4,570,197 shows a surface coating of a fluorinated surfactant and antistatic agent on polymeric materials to reduce static charging. U.S. Pat. No. 4,266,015 shows the use of fluorinated polymers as coating materials or additives to coatings to reduce static charging. Many different fluorinated materials have been designed over the years to provide specific types of properties, including antistatic properties.
Certain quaternary nitrogen polyoxyalkylene compounds with perfluorinated sulfonyl anions have been used commercially in water based polymer systems (e.g., polyvinyl alcohol) as antistatic coating materials. These coatings provide reasonable antistatic protection when coated out, but the water-based coating technology has extremely limited areas of utility. The fact that these fluorinated antistatic agents are easily coated out of water-based compositions, and their highly polar and hydrophilic nature do not suggest any utility for organic solvent based, oleophilic polymer coating systems.
U.S. Pat. No. 4,975,363 discloses the use of antistatic agents, including some of the compounds use within the practice of the present invention, as antistatic agents in photographic elements. The use of water, acetone, alcohol or mixtures thereof as solvents is shown on column 13, lines 28-35.
SUMMARY OF THE INVENTION
The antistatic properties of polymeric films, particularly polymeric film base used for imaging systems, and particularly photographic polymeric film base may be improved by the use of a coating comprising an organic solvent-based film forming polymeric binder and at least 0.005% by weight of a di-quaternary nitrogen polyoxyalkylene compound having highly fluorinated alkylsulfonyl anions. This coating layer may also be used as an auxiliary layer in a photographic element, such as an antihalation layer, so that a single layer provides two functions to the photographic element.
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Austin Steven R.
Gomez Charles W.
3M Innovative Properties Company
Nakarani D. S.
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