Coating apparatus – Gas or vapor deposition – Running length work
Patent
1992-11-02
1994-05-24
Hearn, Brian E.
Coating apparatus
Gas or vapor deposition
Running length work
118719, 118723E, 118730, 118733, C23C 1650, C23C 1654
Patent
active
053145399
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to plasma treatment of material, and in particular to an apparatus for continuous treatment of continuous material with a plasma of a plasma gas under vacuum. The invention is applicable to the treatment of photographic support material, whereby transient surface modifications induced by plasma treatment are exploited to enable improved adhesion and coatability of photographic emulsions to the support. The support is particularly a polyethylene coated paper photographic support. It will be convenient to hereinafter describe the invention in relation to this exemplary application, although it is to be appreciated that the invention is not limited to that application.
2. Description of the Related Art
Plasma or glow discharge treatment of material surfaces has-been reported in numerous publications including J. R. Hollahan and A. T. Bell, "Techniques and Applications of Plasma Chemistry", Wiley, N.Y. 1974 and H. Yasuda, J. Macromol. Sci. Chem. A10,383 (1976). Such treatment has also been the subject of a variety of patents including U.S. Pat. Nos. 3,057,795, 3,288,638, 3,475,307, 3,526,583, 3,761,299, 3,837,886, 3,944,709, 4,437,324, 4,451,497, 4,457,145 and 4,551,310, and British Patents 997093 and 1579002.
The discharges occuring during treatment may be struck in most gases using voltages from several hundred volts to several kilovolts. Pressures are usually in the range 1.33 to 1333.22 pascal (0.01 to 10 Torr) and discharge frequencies range from DC to 100 MHz. In most cases of interest here, the treatment affects the surface properties of materials by modifying the chemical nature of the surface layer. Plasma treatment may be used to improve the bonding of coatings such as adhesives, dyes, inks, polymers and photographic emulsions, to improve the wettability of hydrophobic materials or to alter mechanical properties such as the coefficient of friction or the cohesiveness of textile fibres. In another variation, thin polymer films may be deposited on most surfaces by plasma polyermization from a discharge in an appropriate gaseous monomer. Apart from their potential use as bonding layers, such thin films find other possible uses including protective and decorative layers, optical coatings, capacitor dielectrics and semipermeable membranes.
Few of the reported applications of plasma treatment have utilized any short-lived properties (lasting for up to several hours) of the treated surfaces in subsequent processes. It has been shown, for example in British patent 997093, that surface radicals are produced by plasma treatment of a wide range of organic materials and can be used to initiate graft polymerization if the treated surface is exposed to monomer vapor a short time after treatment. Studies have also shown that surface hydrocarbon radicals are rapidly destroyed in most cases by exposure to oxygen but allylic, polyenyl and peroxy radicals which can be formed in this process may survive for time periods longer than several minutes. The prior art literature does not appear to contain any reference to the possibility of using such short-lived species to react with coatings or films which are rapidly applied to a treated surface. These applications would appear to be of a different nature than those of graft polymerization in that radicals are not used to initiate polymerization but are merely allowed to react with molecules brought adjacent to the surface.
In the photographic industry, the wetting and adhesive properties of hydrophobic (unsubbed) photographic support such as polyethylene coated paper has traditionally been improved prior to coating by subjecting the support to Corona Discharge Treatment. The corona can be formed in air at atmospheric pressure by subjecting an electrode above a dielectric covered roller to a high voltage (15 KV peak) low frequency (10 KHz) signal.
As well as improving the wetting by, and the adhesion to, aqueous photographic emulsion layers, corona discharge treatment introduces strongl
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Brown Robert W.
Coopes Ian H.
Fusca Joseph
Gifkins Kenneth J.
Irvin John A.
Baskin Jonathan D.
Eastman Kodak Company
Hearn Brian E.
Ruoff Carl F.
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