Abstract:
Methods and apparatus for plasma modifying a substrate are disclosed along with associated techniques for applying coatings to the substrate. Particular utility has been found using a hollow cathode to generate the plasma along with magnetic focusing means to focus the plasma at the surface of a substrate.

Description:
This application claims benefit of Provisional Application Ser. No. 60,184,769 filed May 8, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates generally to structures and their components which have been treated with equipment and techniques that produce modifications to surface characteristics in either the structures or the components. More particularly, the present invention relates to equipment and techniques for treating substrates and components having commercial and industrial uses, particularly in industrial fabrics. Most particularly, the invention relates to plasma treated components and substrates together with equipment and techniques useful in treating the same in an efficient and accurate manner. 
     The prior art has recognized the advantages to be obtained by plasma treating and deposition techniques, at low pressure and at atmospheric pressure, to achieve desirable characteristics in a product. Most generally, the products treated in the prior art are single purpose products which were not intended to be exposed to a working condition or an active environment where the treated product is subjected to varying conditions over an extended time period. Furthermore, the prior art products were not exposed to varied treatment over time in a work environment. For example, industrial fabrics are frequently required to work under conditions of high mechanical stress and hostile environments. Special applications, like papermaking, require industrial fabrics that generally work in hot, moist and chemically hostile environments. As such, the fabric may be exposed to high water content in a formation step, heat, pressure and relatively high water content in a pressing step, and then, exposed to high temperatures in a drying step. Thus, the fabrics may see a variety of conditions in the process. Industrial fabrics may also be exposed to varying conditions in industries such as food processing, waste treatment, assembly line processes or surface painting and treating techniques. 
     The art has recognized that it would be desirable to have substrates and components with certain mechanical properties, such as strength, dimensional stability, and flexibility over extended periods. While these characteristics are desired as properties, it is sometimes desired to have surface properties which are contrary to these properties. For instance, it may be desirable to have a component which exhibits good internal resistance to moisture at its core while having an external affinity for moisture at its surface. It is not uncommon to have a conflict develop between the desired mechanical properties and the preferred surface properties. The prior art has recognized and there have been attempts at producing a mechanically robust core which supports a surface layer that has specific characteristics for the desired application. It has been recognized that important surface layer properties such as hydrophilicity, hydrophobicity, oleophilicity, oleophobicity, conductivity, chemical resistance and abrasion resistance may not necessarily be optimized in a single component which optimizes core properties such as strength, flexibility, and the like. 
     The present invention addresses the shortcomings of the prior art by providing structures and components which are treated with a highly efficient and controllable plasma treatment. If desired, the structure or component may be further enhanced or modified by exposure to a deposition treatment. 
     SUMMARY OF THE INVENTION 
     The present invention provides substrates and components having at least one inherent surface characteristic thereof modified by equipment and techniques which are particularly suitable for achieving that modification. The inherent surface property may be modified by a plasma treatment process which comprises the steps of providing a plasma treatment chamber which includes one or more hollow cathodes for generating a plasma within the chamber. The chamber includes means for focusing the generated plasma at the surface to be treated as it is introduced into the chamber and reacted with the plasma. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation showing a plasma treatment apparatus in accordance with the present invention in an opened condition. 
     FIG. 2 is an elevation of the other side of the plasma treatment apparatus of FIG. 1 taken along the line  2 — 2  of FIG.  1 . 
     FIG. 3 is an elevation of one side of the plasma treatment apparatus of FIG. 1 taken along the line  3 — 3  of FIG.  1 . 
     FIG. 4 is a side elevation of one arrangement for treating a substrate in accordance with the present invention. 
     FIG. 5 is a partial cutaway perspective view of a capillary drip system. 
     FIG. 6 is a side elevation of a solution bath. 
     FIG. 7 is an elevation, similar to FIG. 2, showing a plurality of discrete substrates being treating simultaneously. 
     FIG. 8 shows a plurality of substrates A-F in cross-section with or without plasma treating and secondary coating. 
     FIG. 9 shows an alternative arrangement of the plasma treatment chamber. 
     FIG. 10 shows a treatment chamber for metal deposition. 
     FIG. 11 shows a treatment chamber for vapor deposition of a monomer. 
     FIG. 12 shows a curing unit. 
    
    
     GLOSSARY 
     A component is a structural or modular element that is capable of producing a structure when a plurality thereof are assembled together. 
     A fabric structure is formed by arranging individual strands in a pattern, such as by weaving, braiding, or knitting. 
     A fiber is a basic element of a textile and is characterized by having a length at least 100 times its diameter. 
     A filament is a continuous fiber of extremely long length. 
     A hollow cathode is an energy efficient chamber for generating a plasma. 
     An industrial fabric is one designed for a working function such as transport devices in the form of a moving or conveying belt. 
     An inherent property or characteristic is one that exists prior to any treatment by plasma or other means. 
     A monofilament is a single filament with or without twist. 
     A multifilament yarn is a yarn composed of more than one filament assembled with or without twist. 
     A nonwoven structure is a substrate formed by mechanical, thermal, or chemical means or a combination thereof without weaving, braiding, or knitting. 
     A plasma is a partially ionized gas; commonly ionized gases are argon, xenon, helium, neon, oxygen, carbon dioxide, nitrogen, and mixtures thereof. 
     A strand is a filament, monofilament, multifilament, yarn, string, rope, wire, or cable of suitable length, strength, or construction for a particular purpose. 
     A structure is an assemblage of a plurality of components. 
     A substrate is any structure, component, fabric, fiber, filament, multifilament, monofilament, yarn, strand, extrudate, modular element, or other item presented for plasma treatment or coating. 
     A web is an array of loosely entangled strands. 
     A yarn is a continuous strand of textile fibers, filaments, or material in a form suitable for intertwining to form a textile structure. 
     A 100% solids solution is a fluid such as a monomer, combination of monomers or other coating material which includes no carriers or solvent. 
     A 100% solids bath is a tank filled with a fluid such as a monomer, which includes no carriers or solvent. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments will be described with reference to the drawing Figures wherein like numerals indicate like elements throughout. 
     With reference to FIG. 1, there is shown plasma treatment chamber  2  which is useful in accordance with the present invention. Plasma treatment chamber  2  is divided into a plasma generating side  4  and a plasma focusing side  6 . In use, the plasma generating side  4  and the plasma focusing side  6  are joined together in a sealed relationship except for openings  8  and  10  at the respective upper and lower ends. Entry and exit openings are created by the recesses  12 ,  14 ,  16  and  18 . Since the pressure in the plasma treatment chamber  2  is preferably below atmospheric pressure, the recesses  12 ,  14 ,  16  and  18  will be provided with air locks of foam material or loop pile material, such as is available under the trade name Velcro®. Presently, a closed cell polyolefin, such as polyethylene or polypropylene, foam is preferred. When chamber  2  is closed, the walls  20  and  22  will form a channel  24  through the apparatus  2 . A substrate passing between the air locks at openings  8  and  10  will pass into channel  24  and be sufficiently sealed against the atmosphere so as to maintain the desired vacuum level within the plasma treatment chamber  2 . The vacuum in chamber  2  is drawn through the outlet ducts  30  and  32  by a suitable vacuum generating device as will be known to those skilled in the art. Currently, the plasma is being generated between 900 milli torr (0.900 torr) and 3 torr. In earlier trials, plasma was generated at up to 34 torr. 
     With reference to FIG. 2, taken along line  2 — 2  of FIG. 1, there is illustrated a substrate  3  as it passes through the plasma treatment chamber  2  and the hollow cathode assemblies  36 . As shown in FIGS. 1 and 2, the hollow cathode assemblies  36  define multiple hollow cathodes  38 . The plasma generated in the hollow cathodes  38  will be initially focused in the vicinity of the substrate  3 . Additional focusing of the plasma on the substrate is accomplished by the focusing means included in plasma focusing side  6 . 
     Turning now to FIG. 3, there is a view of the plasma focusing side  6  of plasma treatment apparatus  2  that is taken along the line  3 — 3  of FIG.  1 . The plasma focusing side  6  includes a plurality of focusing arrays  50  which are located in space relative to each other so as to achieve a reinforcement of the magnetic focusing field. Surrounding the magnets  50  (shown in crosshatch for clarity) are the cooling ducts  52  which serve to control the temperature in the chamber, thereby protecting the magnets from overheating. 
     Plasma treatment to remove low molecular weight material or surface impurities will preferably use readily available, inexpensive, environmentally benign gases. In some applications, plasma treatment alone may be sufficient, however, it can be followed by coating with metals, ceramics, or polymerizable compounds. Preferred polymerizable compounds are radiation curable organic monomers containing at least one double bond, preferably at least two double bonds, especially alkene bonds. Acrylates are particularly well-suited monomers. Metals suitable for deposition include, but are not limited to Al, Cu, Mg, and Ti. Ceramics suitable for deposition include, but are not limited to, silicate-containing compounds, metal oxides particularly aluminum oxide, magnesium oxide, zirconium oxide, beryllium oxide, thorium oxides, graphite, ferrites, titanates, carbides, borides, silicides, nitrides, and materials made therefrom. Multiple coatings comprising metal, ceramic or radiation curable compound coatings are possible. 
     Plasma treatment leads to one or more of the following benefits: cleaning, roughening, drying, or surface activation. Plasma treatment can also lead to chemical alteration of a substrate by adding to a substrate or removing from a substrate, functional groups, ions, electrons, or molecular fragments, possibly accompanied by cross-linking. 
     All materials are of interest for plasma treatment or application of a secondary coating. Those of primary interest are polymers, such as aramids, polyesters, polyamides, polyimides, fluorocarbons, polyaryletherketones, polyphenylene sulfides, polyolefins, acrylics, copolymers and physical blends or alloys thereof. Preferred secondary layer coating thickness for polymers is in the range of 0.1 to 100 microns, more preferably 20 to 100 microns, most preferably 20 to 40 microns. Preferred metal or ceramic secondary layer coating thickness is in the range of 50 angstroms to 5 microns, more preferably 100 to 1000 angstroms. A preferred polymer is an acrylate of acrylic acid or its esters. The preferred acrylates have two or more double bonds. 
     Monoacrylates have the general formula                           
     Wherein R 1 , R 2 , R 3 , and R 4  are H or an organic group. 
     Diacrylates are acrylates of formula I wherein either R 1 , R 2 , R 3 , or R 4  is itself an acrylate group. Organic groups are usually aliphatic, olefinic, alicyclic, or aryl groups or mixtures thereof (e.g. aliphatic alicyclic). Preferred monoacrylates are those where R 1 , R 2  and R 3  are H or methyl and R 4  is a substituted alkyl or aryl group. 
     Preferred diacrylates have the formula                           
     where R 1 , R 2 , R 3 , R 5 , R 6 , R 7  are preferably H or methyl, most preferably H. 
     R 4  is preferably C 2 -C 20  alkyl, aryl, multialkyl, multiaryl, or multiglycolyl, most preferably triethylene glycolyl or tripropylene glycolyl. The notation, C 2 -C 20  alkyl, indicates an alkyl group with 2 to 20 carbon atoms. 
     R 4  in a mono- or multiacrylate is chosen to yield the desired surface properties after the monomer has been radiation cured to form a surface on a substrate. Table 1 contains a non-limiting list of examples. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 R 4   
                 Surface Properties 
               
               
                   
               
             
             
               
                 —CH 2 CH 2 CH 2 OCH 2 CH 2 CH 2 OCH 2 CH 2 CH 2 — 
                 Abrasion Resistance 
               
               
                 —CH 2 CH 2 OCH 2 CH 2 OCH 2 CH 2 — 
                 Abrasion Resistance 
               
               
                 —CH 2 CH 2 COOH 
                 Hydrophilicity 
               
               
                 —CH 2 CH 2 OH 
                 Hydrophilicity 
               
               
                   
               
             
          
         
       
     
     Formula I and II can also include triacrylate and other polyacrylate molecules. Mixtures of diacrylates can be copolymerized, for example a 50:50 mix of two structurally different diacrylates. Diacrylates can also be copolymerized with other polymerizable components, such as unsaturated alcohols and esters, unsaturated acids, unsaturated lower polyhydric alcohols, esters of unsaturated acids, vinyl cyclic compounds, unsaturated ethers, unsaturated ketones, unsaturated aliphatic hydrocarbons, unsaturated alkyl halides, unsaturated acid halides and unsaturated nitriles. 
     Diacrylates of interest also include 1,2-alkanediol diacrylate monomers of formula                           
     Where R 1  is in an acrylate radical having about 8 to 28 carbon atoms and R 2  is hydrogen or methyl (See for example U.S. Pat. No. 4,537,710). 
     The agent for promoting polymerization may be radiation, such as UV radiation or electron beam radiation. In some instances, it may be preferred to use a photoinitiator, such as an appropriate ketone. 
     Acrylate-based formulations of interest also include heterogeneous mixtures. These formulations contain a very fine dispersion of metal, ceramic, or graphite particles. These coatings are designed to enhance the abrasion resistance and/or the conductivity of the surface. For the photo-curing (UV/Visible) of these pigmented dark acrylate-based formulations, a long wave length (&gt;250 nm) radiation source in combination with a compatible photoinitiator may be preferred. 
     Turning now to FIGS. 4 and 5, there are illustrated apparatuses for sequential plasma treatment, coating, and curing of a continuous substrate which may most easily be thought of as a strand  3 . In FIG. 4, a plasma treatment apparatus  2 , a coating applicator  60 , and a curing unit  70 , provide an integrated system for treatment of the strand  3 . The direction of movement of the strand  3  is indicated by the in and out arrows. The strand  3  moves over a guide roller  88  and enters the plasma treatment apparatus  2  at the opening  8 . To achieve uniform coverage, the strand  3  will not touch either wall  20  or wall  22 . However, the strand  3  will pass closer to wall  22  than to wall  20 . If it is desired to treat only one surface of a strand, the surface to remain untreated may be shielded, such as by contact with wall  22 . After the strand  3  passes through channel  24 , it exits the plasma apparatus  2  through opening  10 . 
     In the preferred embodiment, the coating applicator  60 , is a capillary drip system  400  including a reservoir  402 , a pump  404 , a dispensing manifold  406 , a plurality of capillary tips  408 , and a separating roller  410  having a plurality of grooves  412  dimensioned to receive a substrate as shown in FIG.  5 . The coating solution  61  is pumped from the reservoir  402  into the dispensing manifold  406  and through the plurality of capillary tips  408 . Each tip  408  is associated with a groove  412  in the separating roller  410 . In this arrangement, the roller  410  may rotate or be held stationary. The strand  3  is directed to engage the roller  410  horizontally or at an angle up to 45° above horizontal. The strand  3  travels around the roller  410  and continues vertically upward into the curing unit  70 . The variation in the initial angle θ determines how the strand  3  is coated. Depending on the angle θ, the strand contacts 25-50% of the roller  410  circumference. Use of this capillary tip system is accurate and efficient, requires less coating solution  61 , and provides a more uniform coating than other methods. This approach is believed to be beneficial because it allows for remote location of the reservoir  402  away from potential curing radiation which may impact a dip bath. 
     Returning to FIG. 4, the strand  3  then passes enters into the curing apparatus  70  through channel  72  and passes out of the apparatus at channel  74 . The channels  72  and  74  are defined by the extensions  75  and  76 . The central channel  77  is defined by the walls  78  and  79  of the curing apparatus  70 . After passing the last guide roller  88 , the strand  3  is handled in the usual manner associated with normal production of an unmodified product. 
     In one embodiment, curing apparatus  70  has one section  80  with a plurality of UV lamps (one lamp is noted as  82 ) and an opposed section  84  with a plurality of opposing mirrors (one mirror is noted as  86 ). In a preferred arrangement for curing certain monomer coatings, there are up to four lamps, in opposed pairs. Each lamp is preferably adjustable for controlling their combined output. The sections  80  and  84  are hinged relative to each other to allow access for startup and repair. The UV light used for curing preferably emits radiation between 150 and 400 nanometers. The series of guide rollers  88  change the direction of the strand  3  so it passes continuously through plasma treatment apparatus  2 , coating applicator  60 , and curing apparatus  70 . 
     The system components, plasma treatment apparatus  2 , coating applicator  60 , curing apparatus  70 , and rollers  88 , are secured in a stable manner to preserve the special relationship between them. 
     FIG. 7 illustrates the case for multiple strands  3 , such as monofilaments, passing through the plasma treatment apparatus  2 . The strands are spaced across the width, preferably in individual paths, so that the entirety of the strand is exposed to treatment. The individual strands are preferably guided by grooves cut in the rollers  88 . Using a series of grooved rollers  88  keeps the strands in the desired relationship as they move through the treatment process. 
     The treated substrate is tested according to Test Method 118 developed by the American Association of Textile Chemists and Colorists (AATCC). Drops of standard test liquids, consisting of a selected series of hydrocarbons with varying surface tensions, are placed on the surface and observed for wetting, wicking, and contact angle. The oil repellency grade is the highest numbered liquid which does not wet the surface. The method was modified to test for water repellency, using test liquids of isopropanol and water in ratios of 2:98, 5:95, 10:90, 20:80, 30:70, and 40:60 (in percent by volume) numbered one through six respectively. If surface wetting does not occur within 10 seconds, the next test liquid is applied. Lower ratings indicate oleo-or hydrophilicity while higher ratings indicate oleo-or hydrophobicity. 
     EXAMPLE 1 
     Using a continuous treatment system shown in FIGS. 1-5, a plurality of strands are treated. An extruder is adjusted to produce 10 ends of a polyethylene terephthalate monofilament with a nominal size of 0.26 mm×1.06 mm. These sizes have a tolerance of 0.22-0.304 mm and 1.01-1.11 mm respectively, with an expected yield of 2900 denier. Additionally the yarn would have a relative elongation at 3 grams per denier of 19%, and a free shrinkage at 200 degrees Centigrade of 6.5%. The production speed of the extruder line is set at 216.8 fpm, with the godet rolls and oven temperatures appropriately adjusted to give the specified yarn. 
     Immediately after exiting the extruder, nine of the ten strands are introduced into the plasma chamber, which is at 1.01 Torr, with constant induction of 400 ml/min of commercial grade Argon. The amplifier and tuner are adjusted to introduce 1326 Watts to the hollow cathode, with less than 10 Watts of reflected power. An external chiller is used, which maintains the temperature near room temperature, but above the dew point. 
     Upon exiting the plasma chamber, the nine ends are then directed to a grooved separator roll where monomer is applied. From a one inch manifold being supplied formulation MM2116 by a diaphragm pump, nine capillaries drop to individual grooves spaced evenly across the roller. The air-operated pump is adjusted with a micro air valve to supply a steady state of monomer to the monofilament. A weighing device is used to continually monitor the amount delivered. Coating thickness can be controlled by increasing or decreasing pump pressure, fiber speed or stopping the rotation of the roller. 
     After coating, the yarn proceeds directly upward, and enters the ultra violet cure box, which has three lamps operating. Two lamps are set on medium, and one is set on high, providing an immediate and complete cure of the monomer. In the upper section, two of the lamps are opposed to each other rather than having one lamp opposed by a mirror. Other applications may demand more or fewer lamps. 
     After the yarn exits the UV chamber, it continues down the line through a nip roll and onto the spools mounted on a conventional spool winder. 
     This particular run experienced an increase in the minor axis of 0.0274 mm and in the major axis of 0.1486 mm, causing an increase in weight of 178 grams per 9000 meters or approximately a 5.8% add on. 
     The resulting yarn has an oil, water rating of 4, 6 when tested with AATCC Test Method #118. The yarn was then woven into a filling float fabric using conventional processing methods. The yarn survives the rigors of warping and weaving without abrasion, or flaking indicating the coating is securely affixed. Resulting fabrics also have an oil, water rating of 4, 6 on one surface designated as the face. The untreated PET control has an oil, water rating of 0, 2-3. 
     In this particular example, a series of acrylate-based fluorinated monomer/oligomer formulations have been tested for this application. These materials cover a broad range of surface energies (hydrophobic/hydrophilic and oleophobic/oleophilic), crosslinking densities, abrasion resistance and adhesion to the substrate. 
     The formulation Sigma-MM-2116 is a solvent-free, acrylate based monomer/oligomer mix which contains 50-95% perfluorinated monoacrylate with fluorine content ranging from 30-64%. The formulation also contains 3-50% multi-functional, compatible crosslinking agents, e.g. di- and tri-acrylate monomers. Also 1-20% of an adhesion promoter was added to enhance diacrylate monomers functionalized with hydroxyl, carboxyl, carbonyl, sulfonic, thiol, or amino groups. The high fluorine content lowers the surface energy of the cured coating and turns the coated yarn into hydrophobic and oleophobic material. Combining the plasma treatment of the surface of the substrate with the functionalization of the coating with a specialty adhesion promoter formulation helps to achieve an excellent adhesion between the coating and the substrate while keeping the energy low, making the surface of the substrate both hydrophobic and oleophobic. 
     In addition to the formulation for hydrophobicity/oleophobicity, formulations are also contemplated in applications for electrostatic dissipation and abrasion resistance. 
     Although the presently preferred embodiment uses the capillary drip applicator, initial efforts called for a monomer bath. As shown in the sectional view of FIG. 6, the bath  418  is essentially a tub  420  for holding the monomer solution  61  and a submersible frame  422  for controlling passage through the monomer solution  61 . The frame  422  moves horizontally on shaft  424  and vertically on shaft  425 . The depth of roller  426  in the monomer solution  61  may be controlled by fixing the position of shaft  425 . When the roller  426  is submerged in the monomer solution  61 , each strand  3  is passed around the roller  426  so that it will exit vertically from the bath as indicated by the broken line. 
     EXAMPLE 2 
     Using a continuous treatment system as shown in FIGS. 1 to  5 , a polyethylene terephthalate (PET) monofilament of 0.5 mm diameter is treated. In this example, a sample monofilament is fed from the final extrusion process directly to the plasma treatment apparatus. The control sample is fed from the final extrusion process directly to a wind up roll. As used herein, directly means the absence of intermediate processing steps or storage between processing steps for an extrudate. The line speed in the test system is 200 ft/min but speeds up to 700 feet/min are employed during production. The gas in the plasma treatment apparatus may be 10% argon and 90% nitrogen but is more preferably 20% oxygen and 80% argon. The gas is introduced into the treatment chamber at a rate sufficient to achieve a stable plasma. The vacuum pressure is 10 −1 -10 −4  torr. Power supplied to the plasma chamber is about 2 kW (kilowatts). The power is created with direct current or alternating current but is preferably created with an alternating current in the range of 10 to 100 kHz, with 40 kHz being preferred. The monomer bath contains a solution of triethyleneglycol diacrylate. The lamps in the UV treatment apparatus are 15 inch Hanovia high pressure Hg lamps that generate 300 W/inch. 
     The treated monofilament is compared to the control monofilament by surface tension measurements using the oil and water tests described above. 
     It is preferred to use continuous or in-line processing where the substrate moves through the base processing step, such as extrusion, and plasma/coating treatment at the same speed. 
     Other alternative coating means may be used such as U shaped applicators, a kiss roll, eyelet applicators, and clamshell eyelet applicators. In a more traditional finishing device, the strand passes through a liquid-filled U-shaped device, and emerges with a coating around its entire perimeter. Where capillary action can be used to carry a coating around the strand, a kiss roll applicator may be used. In this technique, the strand is coated when it “kisses” a liquid covered roller which is rotating with or against the strand&#39;s direction of travel. In yet another embodiment, the strand passes through an eyelet through which the coating is pumped. The eyelet may have a clam-shell design to avoid the need for threading the strand through the eyelet. 
     FIGS. 8A through 8G illustrate exemplary cross-sections of coated strands which are producible in accordance with the above example. All cross-sections are greatly exaggerated to permit demonstration of the point. In FIG. 8A, the substrate  302  has a plasma-treated outer surface  303  surrounded by a coating layer  304 . More than one type of coating may be applied through repeated coating techniques. In FIG. 8B, the usually preferred embodiment, the first coating layer  304  and a secondary coating  306  surround the core  302 . In FIG. 8C, the outer layer  306  is disposed only partly around the first coating layer  304 . In FIG. 8D, the first coating  304  and the secondary coating  306  are disposed only partly around core  302 . In FIG. 8E, the coating layer  304  is only partly around the core  302  but the coating  306  is completely around the core  302 . 
     FIG. 8F illustrates exemplary cross-sections of rectangular strands. In FIG. 8F, the plasma-treated substrate  302 , like in  7 B, is coated with a first layer  304 , such as a metal or polyacrylate, and a second layer,  306 , such as a metal or polyacrylate. In FIG. 8G, like  7 D, the substrate  302  is covered for a portion thereof by a first layer  304  and a second layer  306 . Depending on the substrates dimensions, the cross-section in FIG. 8G can resemble that of a thin film. 
     In general, the coating is nonconformational. That is, it will tend to be self-leveling and will not conform to the geometry of the substrate. 
     FIGS. 9-12 show alternative plasma treatment chambers and coating and curing units. 
     FIG. 9 shows a representative upper chamber,  126  and a representative lower chamber,  127 , to illustrate one treatment arrangement. In FIG. 9, upper chamber  126  has the hollow cathodes arrays  36  and  36 , and lower chamber  127  has focusing magnets  50 . The arrangement of FIG. 9 will plasma treat only the upper surface  98  of a substrate  97  when it is relatively dense. For an open, less dense substrate, like a web or open fabric, it may be possible to treat surfaces  98  and  99  at one time. 
     If desired, additional hollow cathodes arrays  36  may be located in the adjacent lower chamber and additional focusing magnets  50  may be located in the adjacent upper chamber  126 , to simultaneously treat upper surface  98  and lower surface  99 . FIG. 9 does not show a gas feed connection for introducing gas to be ionized or electrical connections linked to the cathodes as these connections will be known to those skilled in the art as a matter of design choice. 
     FIG. 10 shows a representative upper chamber  128  and a representative lower chamber  129  in an arrangement for metal deposition. Lower chamber  129  has resistively heated boats  171  and a supply of aluminum wire  173  on spool  175 . As the wire  173  contacts the resistively heated boats  171 , the wire is vaporized. It then condenses on the lower surface  99 . Alternatively, one can create a ceramic coating by introducing oxygen in to chamber  129  to oxidize the aluminum and create aluminum oxide (Al 2 O 3 ). 
     FIG. 11 shows a representative upper chamber  124  and a representative lower chamber  125  for creating a monomer layer on surface  98 . A monomer vaporizer  180  creates a cloud of monomer vapor which will be deposited through condensation on the upper surface  98 . If desired, a vaporizer  180 , shown in phantom could be located as a mirror image in lower chamber  125 . 
     FIG. 12 shows a representative upper chamber  130  that has a bank  82  of UV emitting lights that irradiate and cure the monomers on surface  98 . Alternatively, the radiation device can be one that emits an electron beam. If the substrate is treated on both surfaces a second bank  190 , as shown in phantom will be located in chamber  131 .