Apparatus for plasma treatment

Abstract: An apparatus for plasma treatment of long continuous materials, typically sheet materials, which comprises a plasma treatment chamber (A), an electric power introducing member (1) positioned in the central portion of said chamber (A), a plurality of antenna electrodes (4) radially extending from the vicinity of said electric power introducing member (1), a plurality of grounded electrodes (5) each facing a treating surface of said antenna electrodes (4), said electric power introducing member (1) being connected with respective ends close thereto of said antenna electrodes (4), and a guide means, e.g., guide rolls (6;7), for passing treating materials (8) through gaps between said antenna (4) and groundes electrodes (5). The antenna electrodes (4) preferably have curved surfaces bulging out with respect to the direction of the travel of the treating materials (8).

Description: The present invention relates to an apparatus for conducting continuous plasma treatment of long materials. More particularly, this invention relates to an apparatus for conducting continuously plasma treatment of long materials, such as membranes, films, sheets, fabrics, fibers or the like, particularly long and flat materials relatively small in thickness and large in width (may be referred to as "treating material", hereinafter). As an apparatus for plasma treatment, particularly of flat sheet-like materials or long materials, a host of proposals heretofore have been made. For example, in US-A-4 550 578 (Japanese Patent Application Publication Nos. 11,149/1985 and 31,939/1985), apparatuses for continuous treatment of fabrics with plasma by passing and treating the fabrics between a pair of parallel electrodes having a large surface area have been proposed. Further, in Japanese Patent Application Laid-open Nos. 60-134,061 and 61-228,028, and Japanese Patent Application Publication Nos. 59,251/1985 and 36,862/1986, which corresponds to FR-A-2 487 696, apparatuses for plasma treatment having a plurality of antenna electrodes arranged around a cylindrical grounded electrode have been proposed. Furthermore, in US-A-4 437 324 and US-A-4 550 578 (Japanese Patent Application Publication Nos. 11,150/1985 and 54,428/1985), apparatuses for plasma treatment comprising multi-layered parallel plane electrodes provided up and down alternately for forming zigzag cloth passages have been proposed. However, the proposals made in the above US-A-4 550 578 (Japanese Patent Application Publication Nos. 11,149/1985 and 31,939/1985) include problems, such as uneven treatment caused by local deviations in degree of treatment over the large surface area of the electrodes, a decrease in treating efficiency due to generation of plasma discharges in spaces on upper and lower sides and right and left sides of electrodes, or the like. Further, in the proposals made in the above-mentioned Japanese Patent Application Laid-open No. 60-134,061 and others, the treating area of electrodes cannot be increased so much and discharge losses around antenna electrodes have been inevitable. In the proposals made in the above US-A-4 437 324 and US-A-4 550 578 (Japanese Patent Application Publication Nos. 11,150/1985 and 54,428/1985), lags in phase of high frequency are produced on the respective multi-layered electrodes whereby the high frequencies mutually interfere so that difficulties have been encountered in achieving operations and qualities with stability. Thus, none of the hitherto known apparatuses for plasma treatment can completely satisfy all of the stability of operation, uniformity of quality and treating efficiency of input power. We, the inventors, aiming at elimination of these problems and difficulties, proposed before, as Japanese Utility Model Application No. 62-171,464, an apparatus for plasma treatment which comprises a vacuum vessel, a plurality of antenna electrodes arranged therein having a curved treating surface bulging out with respect to the direction of the travel of treating materials, and grounded electrodes arranged each facing a treating surface of said antenna electrodes, and is provided with a guide means for passing said treating materials through gaps between said antenna electrodes and grounded electrodes. This proposed apparatus succeeded in solving various technical problems in conventional apparatuses. However, as a result of subsequent studies, the inventors have found the necessity of further improvements from aspects of compaction of apparatuses, increase in treating efficiencies, etc. and eventually accomplished the present invention. An object of the present invention is to provide an apparatus for plasma treatment in which, even with a plurality of electrodes, no mutual interferences of plasma occur between respective electrodes and useless and detrimental plasma discharges around the electrodes are suppressed to the utmost. A further object is to provide an apparatus for plasma treatment which can be operated with an improved stability and which can efficiently produce treated materials high in grade and uniformity. The apparatus for plasma treatment to achieve the above objects of the present invention comprises a plasma treatment chamber, a plurality of antenna electrodes arranged therein and grounded electrodes arranged each facing a treating surface of said antenna electrodes, and being provided with a guide means for passing treating materials through gaps between said antenna electrodes and grounded electrodes, said apparatus being characterized in that an electric power introducing member is positioned in the central portion of said plasma treatment chamber, the said antenna electrodes are arranged to radially extend from the vicinity of said electric power introducing member, and said electric power introducing member is connected with the respective ends of said antenna electrodes closest to said electric power introducing member. In the first embodiment of the apparatus according to the present invention, said antenna electrodes have curved treating surfaces bulging out with respect to the direction of the travel of the treating materials. In the second embodiment of the apparatus according to the present invention, said antenna electrodes have flat treating surfaces. In the third embodiment of the apparatus according to the present invention, said grounded electrodes have curved treating surfaces bulging out with respect to the direction of the travel of the treating materials. In the most preferable embodiment of the present invention, said electric power introducing member is enclosed in a limited space defined by a surrounding wall and communicating with an outer atmosphere, which electric power introducing member is connected with said respective ends of the antenna electrodes through said surrounding wall defining the limited space. The treating materials applicable to the present invention are not specifically limited insofar as they are flat and thin material with a relatively small thickness, such as membranes, films, sheets, fabrics or the like or long materials, such as fibers, threads or the like. The above and other objects, features and advantages of the present invention will become more apparent from reading the following description of the preferred embodiments taken in connection with the accompanying drawings, wherein: Fig. 1 is a schematic partial front view showing an embodiment of the present invention; Fig. 2 is a schematic side elevational view of the same; Fig. 3 is a schematic front view of a plasma treatment chamber, a principal part of the apparatus according to the present invention; Fig. 4 is a vertical cross-sectional view showing relative arrangements of an antenna electrode preferably employed in the apparatus of the present invention and means for guiding treating materials; Fig. 5 is a perspective view of an antenna electrode preferably employed in the apparatus of the present invention; Fig. 6 is a vertical cross-sectional view parallel to the side surfaces of the antenna electrode shown in Fig. 5; Fig. 7 is a perspective view showing a surface structure of an electrode manufactured by conventional processes; Fig. 8 is a perspective view showing a surface structure of an electrode preferably employed in the apparatus of the present invention; Fig. 9 is a perspective view showing an improvement of an electrode preferably employed in the apparatus of the present invention; Figs. 10 and 11 are schematic front views showing different embodiments, respectively, of the plasma treatment chamber; Fig. 12 is a schematic front view of a plasma treatment chamber in the most preferable embodiment of the apparatus according to the present invention; Fig. 13 is a schematic side elevational view of the plasma treatment chamber shown in Fig. 12; Figs. 14 and 15 are schematic front views of plasma treatment chambers respectively in modifications of the most preferable embodiment of the apparatus according to the present invention; Fig. 16 is a schematic front view showing an embodiment of the present invention wherein mechanisms for feeding and winding-up the treating materials are provided in the plasma treatment chamber; Fig. 17 is a schematic view illustrating a basic structure of a plasma treatment space defined by grounded electrodes and covers attached therebetween, which is preferably applied to the apparatus of the present invention; Fig. 18 is a schematic front view of a plasma treatment chamber provided with viewing ports; Figs. 19 and 20 are schematic front and side elevational views, respectively, of an apparatus of the present invention which is further provided with closable and openable holes; Figs. 21a and 21b are schematic front views showing electrode arrangements in plasma treatment apparatuses used in comparative tests, wherein Fig. 21a is the apparatus of the present invention and Fig. 21b is a conventional apparatus; and Fig. 22 is a graph showing plots of L-value versus plasma energy with respect to black dyed fabrics plasma-treated with the respective apparatuses shown in Figs. 21a and 21b. In Figs. 1 and 2, a vacuum vessel consists of three parts: horizontal, cylindrical chambers A, B and C. The chamber A is in communication with the chambers B and C via passages 17 and 18, respectively. The chamber A is a plasma treatment chamber. The chamber A is provided with a gas feed pipe 11 and a gas discharge pipe 12 communicating with a vacuum pump (not shown). The chambers B and C accommodate separately a feed roll 9 and a windup roll 10 for a treating fabric 8. The chambers B and C may be united in one that accommodates both the feed roll 9 and windup roll 10. Alternatively, a simple design change will allow the chambers B and C to be omitted, placing everything in the chamber A as shown in Fig. 16. In Fig. 3 illustrating the chamber A in detail, an electric power introducing member 1 is positioned approximately in the central portion of a plurality of antenna electrodes 4. A plurality of electrode connecting members 2 extending from the electric power introducing member support the plurality of antenna electrodes 4 and electrically connect the electric power introducing member 1 with the respective antenna electrodes. The electric power introducing member 1 is electrically insulatedly supported by an insulating bearing 3 and coupled with a terminal 15 of a high frequency source. The electrode connecting member 2 and the antenna electrode 4 are not necessarily aligned with each other. However, it is preferred in view of the balancing of the distribution of electricity that distances from the electric power introducing member 1 to respective antenna electrodes are equal and of the smallest length possible. All of the angles made by two longitudinal axes extending towards peripheral directions of any adjacent antenna electrodes do not have to be equal. However, an equiangular radial arrangement is most preferable. As is shown in Fig. 3, in the first embodiment of the present invention, the antenna electrodes are, in order to bring the treating materials into effective and stable contact with the surfaces thereof, made to have curved surfaces bulging out with respect to the direction of the travel of the treating materials. Curvatures and shapes of the bulged surfaces should be determined adequately depending on length of the electrode, diameter of the feed or delivery guide roll, and transforming feasibility and operating tension of the treating material. However, the longitude of the bulged surface may be a part of an arc or partly vary in curvature so as, for example, to make the treating material contact with the surface of the electrode at a uniform contact pressure. It is enough for the ratio of the height of the middle portion to the length of the electrode to be at least 1/100, more preferably 1/50∼1/10. The guide means for the treating materials, guide rolls 6 and 7, are positioned to bring the treating materials into better contact with the antenna electrode. Additionally, as shown in Fig. 4, it is preferred to provide a means 32 to adjust the positions of a plurality of guide rolls 6, 7 as well as other guide rolls so that the treating material 8 can be brought into contact making an arbitrary angle with the antenna electrode 4. The diameters of the guide rolls 6, 7, etc. are not specifically limited. By providing such a guide roll position adjusting means, for example, slots 32 such as horizontal or vertical bearing slots, lever mechanism, link mechanisms, or the like, electrodes having any curvatures or thicknesses or any distances between electrodes are made adaptable. A grounded electrode 5 facing the antenna electrode 4 may be rod-like or plate-like. However, it is preferred to have a concave surface corresponding to the facing bulged surface of the antenna electrode, more preferably, the same curvature as that of the antenna electrode surface. Thereby plasma discharged between those electrodes can be improved in uniformity so that qualities of treated materials also can be improved in uniformity. The grounded electrodes and antenna electrodes are arranged to extend radially from the vicinity of the central portion of the plasma treatment chamber towards the peripheral direction. The grounded electrodes 5 and the antenna electrodes 4 are arranged preferably to be in parallel with and spaced apart from each other. The spatial distance depends upon treating conditions, such as input powers, shapes of electrodes, degree of vacuum, treating rate or the like, and purposes of treating, such as plasma etching, plasma polymerization, plasma CVD or the like. Generally, in the case where the degree of vacuum and the input energy are low, it is preferably small, usually 10 cm or less, preferably at most 5 cm. For example, in the case of oxygen gas plasma under a degree of vacuum of about 133 Pa (1 mmHg), a spatial distance of about 0.5∼3 cm will be effective. Materials for the antenna electrode 4 and grounded electrode 5 are preferably highly conductive metals, such as aluminum, copper, iron, stainless steel, various metals plated therewith, or the like. Preferable structures of such an electrode will be explained hereinafter with reference to the antenna electrode as an example. In Figs. 5 and 6, the antenna electrode 4 has a contour consisting of both surfaces of metal plate 102 and both sides of side plate 103, and an electric power introducing member 101 attached to the top end thereof. Further, the inside of the electrode is filled with a filling material 105 to be dense enough substantially not to allow the plasma to be produced inside. Here, the expression "to be dense enough substantially not to allow the plasma to be produced inside" should be understood to mean that the electrode is free from any such large voids or cavities as to allow useless plasma to be produced therein. The filling materials having such a degree of density include anything from solid materials free from voids and cavities to somewhat porous materials. From the standpoint of prevention of inside plasma discharging, the solid materials are preferred, while, from the standpoint of weight savings in the apparatus, the porous filling materials are suitable. The porous materials that are dense enough substantially not to allow the plasma to be produced inside may have voids or cavities, for example, when they are voids, with an average diameter of about 10 mm or less, and when they are long cavities, with an average diameter or width of about 5 mm or less, and further when they are broad slit-like cavities, with an average spacing of about 4 mm or less, preferably 2 mm or less. The materials for the filling materials 105 to fill the inside of the electrode with may be those not susceptible to vaporization or decomposition in vacua during plasma treatment, and employable are, for example, metals the same as or different from the material of electrode plates, glasses, ceramics, synthetic high-polymers, resins, rubbers and other organic or inorganic materials. As a form of the filling materials, taking the weight increase into consideration, preferable are porous materials of metals, glasses, ceramics, synthetic high-polymers, resins or rubbers, and most preferable inter alia are porous materials of ceramics, crosslinkable polymers or thermosetting resins. These materials include glasses such as hard glasses, quartz or the like, thermosetting resins such as phenolic resins, urea resins, melamine resins, polyester resins, epoxy resins or the like, thermoplastic resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, nylon, polytetrafluoroethylene, polycarbonate or the like, rubbers such as styrene-butadiene rubber, butadiene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, silicone rubber, fluororubber or the like, ceramics such as alumina, mullite, magnesia, boron nitride, asbestos, diatomite or the like, and ordinary metals. As a shape of the electrode, flat plates, punched metal plates or meshes can be used. However, when the input power is 0.1 W/cm² or more, plane plates without holes or recesses or projections are preferred. This is so in the case where the input power is augmented with the intention of increasing of plasma treatment efficiency, and the antenna electrode 4 as shown in Fig. 7, which is manufactured by customarily used conventional processes, generally has joints 106, clearances, or rivet or bolt heads 107 on the surfaces of which abnormal plasma discharges will be produced. These abnormal plasma discharges will cause ill matchings and damage of treated materials, inducing serious defects in the case of continuous treatment. In order to eliminate such a problem and perform plasma treatments with a high rate and high uniformity in treating efficiency, it is preferred, as shown in Fig. 8, that the whole surface of the antenna electrode 8 is formed with a smooth, uniform and continuous monolithic structure. Such a structure has no ply-up or screw marks and is free form any portions liable to abnormal discharges, such as seams, crevices, pits, projections, or the like. One of the manufacturing processes for obtaining such a structure is monolithic molding. However, when the monolithic molding is difficult to conduct, it is preferred to utilize the monolithic molding to the utmost. Further, seams, crevices and the like 108 formed by welding during the manufacturing process are abraded to be made smooth. Additionally, all edges are preferably beveled to be rounded off. Such structures may prevent abnormal discharges and further it is decreased in electric resistance as compared with screwed structures, so that heat generation in the antenna electrodes having such a structure is reduced. As shown in Fig. 6, it is preferred that the antenna electrode 4 and the grounded electrode 5 are provided on the inside with passages 104 for a temperature controlling medium to effect temperature control, particularly cooling. As the medium, any substances having fluidity can be employed. However, pure water, organic solvents or various gases or vapors for heat exchanging which are electrically insulating are preferable. Alternatively, as temperature controlling devices or cooling devices, it is preferred that a heat exchanging tube or a jacket, in which a coolant is circulated through passages 19 and 20, is provided on the back of a metallic plate 102. By virtue of the temperature control, the substrate temperature can be set at the most adequate temperatures corresponding to the kind of various plasma treatments, such as plasma polymerization, plasma CVD, plasma etching, or the like. Thus, the antenna electrodes can be set at a desired temperature at which the treating fabrics are allowed to contact with the antenna electrodes, so that a stable treatment is performable for a long period of time. The electrode to be applied to the apparatus of the present invention, in order to decrease the abnormal discharges, preferably has insulating layers formed on the surfaces from the end of the electrode approached by the treating material up to the portion where the material just comes into contact with the electrode. Namely, when a long treating material is made to contact and pass over the surfaces of a stationary electrode, it is most preferable to draw the treating material from a tangential direction onto the convex surface of the electrode by adjusting guide rolls in order to avoid damage to the material due to fretting by the tip end of the electrode. However, since electric potential density increases concentratedly towards the end of the electrode, the abnormal discharges are liable to occur over the range from the end of the electrode to the portion where the material just comes into contact with the electrode, causing serial defects in the case of continuous treatment. Such an abnormal discharge will become conspicuous particularly when the plasma power is increased in order to raise the treating efficiency. Therefore, as shown in Fig. 9, insulating layers 109 are formed on surfaces of the electrode the treating material is comes into contact with, for example, preferably on the surfaces of an antenna electrode 4 including the portion with which the treating material just comes into contact. Such an insulating layer 109 is preferably provided at least on the portion where the treating material 8 begins to come into contact with the electrode 4, and more preferably also provided on the other portion where the treated material is pulled off from the electrode. Furthermore, it is most preferable that the insulating layers are formed on surfaces from the end of the electrode approached by the treating material up to the portion where the material just comes into contact with the electrode and also including the delivery end of the electrode up to the portion where the treated material is pulled off. Such an insulating layer 109 consists of a non-conductive material such as ceramics, organic or inorganic high molecular substances or the like. Processes for forming the insulating layers include plating, coating, attaching of film or sheet, mounting of blocks, vapor depositing and the like, and are not specifically limited insofar as the object is fulfilled. The surfaces of the insulating layers are preferably made as smooth as possible to minimize damage to the treated materials. Additionally, hardness and slipperiness depend upon cleanness and treating conditions of the treating materials. For example, if the treating materials are thin films or membranes, the surfaces of the insulating layers are preferably aventurine, easily slippable and not so hard. Employable materials for the insulating materials are, for example, inorganic materials or ceramics, such as glasses, pyrex, fused quartz, steatite, titanium oxide, barium steatite, zirconium oxide or the like, and organic high polymers, such as polystyrene, Teflon®, polyacrylics, polyvinyl chlorides, chlorinated polyethylenes, polyimides, silicones, polyvinyl fluorides, polyethylenes, polypropylenes, polyamides, polyesters or the like. Widths (working widths) of the insulating layers are required to be at least larger than the width of the treating materials, and preferably have side margins of at least 1 cm, more preferably at least 2 cm. The longitudinal widths, namely the lengths, are sufficient if they are long enough to suppress the abnormal discharges. If it is too long, electrode efficiency will decrease. Therefore, it is generally 1/4 or less, preferably 1/6 or less, of the length of the electrode. Alternatively, a thickness generally of about 0.1 mm or more, preferably 1 mm or more, can suppress the abnormal discharges effectively. If excessive crevices or level differences are formed on the borders between the insulating layers and contiguous surfaces, new abnormal discharges may be generated, so that it is preferably free of crevices or level differences. In the second embodiment of the present invention, as is shown in Fig. 10, the antenna electrodes 4 have flat treating surfaces. Angles made by the front and back surfaces are not specifically limited and, however, they are preferably determined to easily make the travelling fabric, which is guided by the guide means explained hereinafter, parallel with the surface of the electrode. In the radial arrangement, all of the angles made by the adjacent antenna electrodes may not necessarily be equalized. However, an equiangular radiation is most preferable. Further, in the third embodiment of the present invention, as is shown in Fig. 11, the grounded electrodes are, in order to bring the treating materials into effective and stable contact with the surfaces thereof, made to have curved surfaces bulging out with respect to the direction of the travel of the treating materials. Curvatures and shapes of the bulged surfaces are preferably determined to be same as the case of the antenna electrodes in the aforementioned first embodiment of the invention. The grounded electrodes 5 facing the antenna electrodes 4 are supported by supporting members 25 on the wall of the plasma treatment chamber or a cover 14. In the most preferable embodiment of the present invention, the electric power introducing member is enclosed in a limited space defined by a surrounding wall and communicating with an outer atmosphere. This electric power introducing member is connected with the respective ends of the antenna electrodes close thereto through the surrounding wall defining the limited space. Thus, in Figs. 12 and 13, the limited space 27 defined by a box or cylinder 26 is provided in approximately the center of a plurality of antenna electrodes 4. The limited space 27 communicates with the outer atmosphere at either or both of the front and the rear of the plasma treatment chamber and accommodates the electric power introducing member 1. A plurality of electrode connecting members 2 extend from the electric power introducing member through the wall of the box or cylinder 26 and support the radially arranged plurality of antenna electrodes 4 with their protruding ends 28. These electrode connecting members electrically connect the electric power introducing member 1 with the respective antenna electrodes and are supported hermetically on the wall of the box or cylinder 26, electrically insulated therewith by insulating materials 29. The electric power introducing member 1 is coupled with a terminal 15 of a high frequency source. It is most preferred that the electric power introducing member 1 is positioned at the center of the limited space 27 defined by the box or cylinder 26 and all of the electrode connecting members 2 extending from the electric power introducing member 1 to the wall of the box or cylinder are in an equiangular radial arrangement. Additionally, it is most preferred as well that the protruding ends 28 extending from the wall of the box or cylinder to the respective antenna electrodes 4 are made as short as possible and all of the same length. The size and length of the above limited space 27, namely, the dimension of the box or cylinder can be designed arbitrarily in accordance with objects and form of the apparatus as well as the kinds and number of pipe-lines for gases, water and the like to be installed in the plasma treatment chamber. Additionally, it is also preferred that the projecting ends 28 are covered by insulating coatings in order to prevent useless discharges. In this embodiment, also the electrode connecting member 2 and the antenna electrode 4 are not necessarily aligned with each other. However, it is preferred in view of the balancing of the distribution of electricity that the distances from the electric power introducing member 1 to the respective antenna electrodes are equal and of the smallest length possible. As shown in Fig. 12, the antenna electrodes are, in order to bring the treating materials into effective and stable contact with the surfaces thereof, made to have curved surfaces bulging out with respect to the direction of the travel of the treating materials. However, as shown in Fig. 14, the antenna electrodes 4 may have flat treating surfaces and be provided with flat surfaced grounded electrodes 5 which are in parallel with both sides of the antenna electrodes 4. Alternatively, as shown in Fig. 15, the grounded electrodes may be made to have curved surfaces bulging out with respect to the direction of the travel of the treating materials to bring the treating materials into effective and stable contact with the surfaces thereof. In Figs. 1 and 2, the chambers B and C, which communicate with the plasma treatment chamber A having the above structure, accommodate a feed roll 9 and a windup roll 10, separately. The windup roll 10 is driven by a motor 16 or the like. It is preferred that the rotation of the feed roll 9 and windup roll 10 is made reversible appropriately by means of a linking mechanism of the motor 16. Fig. 16 shows an embodiment wherein the plasma treatment chamber A accommodates the feeding roll 9 and windup roll 10 so that the chambers B and C are omitted. It may be easy to appropriately design the shape and structure of the plasma treatment chamber A so that it can accommodate the feed roll 9 and windup roll 10. Further, in the plasma treatment chamber A, there are arranged guide means embodied by, for example, guide bars, guide rolls 6 and 7 or the like mounted at appropriate positions near the bases and tops of the electrodes, to guide the treating material 8 from the feed roll 9 to the windup roll 10, successively passing through gaps between the grounded electrodes and the antenna electrodes. As the guide means, stationary rolls, idler rolls, driven rolls or combinations thereof can be appropriately employed in accordance with operating conditions, such as weight, travelling speed, tension or the like of the treating material. It is preferred that these guide means are so adjusted and arranged that the travelling treating material may contact the surfaces of the antenna electrodes or the grounded electrodes. Materials for the rolls 6 and 7 to guide treating materials in the plasma treatment space are preferably, for example, metals, ceramics, metal coated ceramics, or materials coated with NBR, silicone rubbers, or the like, which are low in etching susceptibility and excellent in heat resistance as compared with the treating materials. Further, the rolls are preferably grounded. The rolls preferably have secular surfaces in order to prevent slippage of the treating materials. More preferably, they are coated with silicone rubber, NBR rubber, SBR rubber, fluororubber or the like, or covered by rubber tubes for the purpose of stable travelling and heat prevention of the treating materials. Main structural components such as the antenna electrodes, grounded electrodes, guide means for the treating materials, electric power introducing member, and the like in the vacuum vessel are supported and integrated by a frame 13 and travel on guide rails 23 to be loaded into and unloaded from the vacuum vessel. In the apparatus according to the present invention, it is particularly preferred that covers extending between both side edges and outer edges, respectively, of mutually adjacent two grounded electrodes interposing an antenna electrode therebetween are provided to define a plasma treatment space and gas feed orifices 11 and gas discharge orifices 12 are provided near one end and the other end, respectively, of the grounded electrode in the plasma treatment space. The above covers and gas flow system serve to smoothly orient the gas flow in the plasma treatment space, introducing and directing fresh gases constantly onto surfaces of the treating materials and effectively discharging decomposed gases that generate and otherwise hinder the objective treatment. Fig. 17 shows schematically a basic structural unit of the plasma treatment space defined by grounded electrodes, and covers extending therebetween. In Fig. 17, a plasma treatment space is defined along the treating faces of an antenna electrode 4 by covers 14, 14' extending between both side edges of mutually adjacent grounded electrodes 5, 5' interposing the antenna electrode 4, and by a cover 14'' extending between the both outer edges of the grounded electrodes 5, 5'. In the plasma treatment space, a gas feed pipe 11 is provided in the vicinity of one end of the grounded electrode, preferably the outer end with respect to the aforementioned radial arrangement (the free end side of the antenna electrode). The covers 14, 14', 14'' confine and regulate the fed gas flow between the grounded electrodes. Materials for the cover may be either insulating or conducting, and preferably the same as that of the electrodes, for example, stainless steel, aluminum, copper plates, or the like. The cover is preferably grounded. The distance between the covers and the antenna electrode is preferably larger than the distance between the grounded electrodes and the antenna electrode in view of stability and uniformity of the plasma. It is preferred that the shape of the openings of the gas feed orifices 11 is a long slot or a number of small holes and, further, that the orifices are present over the whole width of the electrodes, for unevenness in ratio of feed gases to decomposed gases can be obviated, resulting in a stable treating performance. As a material for the gas feed pipelines, organic materials such as plastics or the like are employable and, however, in order to use stably for a long period of time, preferable are metals high in chemical stability, plasma resistance and high temperature resistance, such as stainless steel pipes, steel pipes, aluminum pipes, glass pipes or the like. The apparatus according to the present invention is preferably provided on the periphery of the plasma treatment chamber with at least one viewing port through which a gap between an antenna electrode and a grounded electrode can be observed and, more preferably, further provided on the peripheries of chambers with at least one hole equipped with a closable and openable lid. In Figs. 18∼20, at least one viewing port and/or hole 30, in case of a hole, having an openable and closable lid is provided on chambers A, B and/or C. For the window pane of the viewing port to observe plasma discharging and treating material travelling conditions, transparent materials, such as glasses, tempered glasses, transparent ceramics, plastics or the like, are employable. However, materials having an ultraviolet-screening action are preferable. By the observation through the viewing port with the naked eye or with the aid of instruments, accuracy, uniformity and stability of the treatment as well as defects are checked. Thus, voluminous information can be collected in real time, which is not only useful to greatly improve the stability and uniformity of the treatment, but also enlightens defects due to abnormal discharges, abnormal travelling of the treating materials, etc. in advance of the final inspection. Alternatively, the openable and closable holes enable the treating or treated materials to be drawn therethrough out of the chambers to be cut and connected with a sewing-machine so that batch exchange operations can be performed as all structural components, such as electrodes, guide rolls, feed rolls, windup rolls, and the like, are in a fixed condition in the vacuum vessel. In the embodiment shown in Figs. 1∼3 of the apparatus of the present invention, a fabric, the treating material, in the chamber B fed from the feed roll 9, being regulated by the guide roll 21, passes through the passage 17, travels between the electrodes, and then, being guided by the guide roll 22, is wound up on the windup roll 10. In the present invention, the treating material 8 is preferably placed within a plasma sheath formed in the vicinity of the antenna electrode, more preferably within 5 mm from the antenna electrode, and most preferably in contact with the antenna electrode. In conventional processes, since the treating material is arranged on the grounded electrode or between the antenna electrode and the grounded electrode, the spacing from the both electrodes, and the treating rate and effect are low, so that a large scale treating apparatus has been required in order to increase the effect to a certain extent. Further, in the present invention, when the antenna electrodes have bulging treating surfaces with respect to the direction of the travel of the treating materials, contact of the treating materials with the antenna electrodes is remarkably high. Therefore, highly uniform treatments for a short period of time are enabled with a small input. Though the reason why the placing of the treating materials within a plasma sheath, and preferably contacting these with the antenna electrode, produces a good effect, has not been elucidated yet, it is conjectured that a negative self-bias produced in the antenna electrode accelerates positive charged particles in the plasma. Introduction of electric power is performed concentratedly through the electric power introducing member 1. To each antenna electrode 4, the electric power is introduced from the electric power introducing member 1 via the electrode connecting member 2. Since the apparatus has only one electric power introducing member, a singular electric source can be employed to thereby obviate most of the mutual interferences of high frequencies as well as plasma unbalances due to lags in frequency of oscillation etc. between the electric sources that are produced in the case where a plurality of electric sources are used. An electric power having a commercial frequency of 50 Hz for generating plasma, a low frequency of kilohertz or a high frequency of megahertz to gigahertz, is introduced to the antenna electrodes 4 to generate low-temperature gas plasma between the antenna electrodes and the grounded electrodes. For the stable generation of the low-temperature gas plasma, a low frequency or a high frequency is preferred, while a high frequency of 13.56 MHz is particularly preferable in respect of efficiency and cost of treatment. Additionally, the input energy of the low frequency or high frequency depends on the shapes of the electrodes, the distances between electrodes, the degree of vacuum, the treating rates etc. and, however, is usually at least 0.01 W/cm², preferably 0.05∼10 W/cm², more preferably 0.1∼1 W/cm². As a gas for generating low-temperature gas plasma, non-polymerizable gases, such as oxygen, nitrogen, argon, helium, hydrogen or the like, or polymerizable organic monomer gases, such as methane, ethane, propane, butane, benzene, acrylic acid, styrene, or the like, can be employed. These are selected in accordance with the objects. The plasma etching of polyester fibers etc., oxygen, air, nitrogen, argon, hydrogen, carbonic acid gas, helium and halogenated hydrocarbons such as CF₄, CF₂Cℓ₂, CFCℓ₃, CHF₃ and the like can be used alone or in combinations thereof. The degree of vacuum of the plasma treatment space is adjusted to fall in a range in which low-temperature gas plasma is stably generated, namely, usually 1,33∼1333 Pa (0.01∼10 mmHg), preferably 13,3∼667 Pa (0.1∼5 mmHg), and more preferably 26.6∼133 Pa (0.2∼1 mmHg). The degree of vacuum can be adjusted by the gas or monomer gas feed rate as well as the gas discharge rate. However, adjustment by means of the gas feed rate is more preferred in order to perform the objective treatment satisfactorily. The gas feeding is conducted preferably by blowing gases onto the treating surfaces of the treating material. Thereby, the treating surfaces of the treating material contact constantly with the fed fresh gases and, further, decomposed gases produced by the plasma treatment are efficiently discharged from the plasma treatment space. The ratio of feed gas to decomposed gas is at least 1, preferably at least 2, more preferably at least 4. An increase in efficiency and the prevention of extraneous reactions are largely influenced by how plasma is generated efficiently from the fed gases to be applied to surfaces of the treating material, and by how the decomposed gases are removed from the surfaces of the treating material and discharged efficiently. The covers 14 extending between adjacent grounded electrodes serve to efficiently replace the decomposed gases with the fed gases. Conspicuous functions and effects of the present invention will be demonstrated hereinafter by way of examples in which the apparatus of the invention is applied. Example 1 A georgette fabric composed of a 60d/48f polyester filament warp yarn having an S-twist of 250 T/M and two kinds of 75d/72f polyester filament weft yarns having S- and Z-twists of 3000 T/M, respectively, was crimpled in a washer according to a conventional process and then heat-set to dry at 180°C. The fabric was further scoured with 20% caustic soda aqueous solution at 90°C to reduce the weight of the fabric by 20%. The resulting fabric was dyed with 15% o.w.f. of Kayalon Polyester Black GSF (trade name of dyestuff manufactured by Nippon Kayaku Co., Ltd.) and then subjected to a reduction washing to provide a black dyed georgette crepe fabric. Then, an aqueous dispersion liquid of a mixture of amino modified silicone resin and partially fluorinated acrylic resin with a mixing ratio of 1:1 which had good mutual miscibility and mutual incompatibility, showing micro-phase separation, was applied onto the above fabric to an amount, as resin, of 1% o.w.f. by soaking according to a conventional process. After drying, the fabric was heat-treated at 150°C to fix the resins. Then, using plasma treatment apparatuses provided with electrodes having a shape and arrangement respectively shown in Figs. 21a (radial arrangement of the present invention) and 21b (parallel arrangement of a conventional apparatus), the above fabric was treated with plasma by being brought into contact with the antenna electrodes under the following conditions. On the outset, after evacuating the vacuum vessel to 1,33 Pa (10⁻² torr) by a vacuum pump, O₂ gas was introduced into the vacuum vessel to adjust the pressure in the vessel to 40 Pa (0.3 torr). Then, a high frequency power of 13.56 MHz was applied to the antenna electrodes. The output of the high frequency power and the treating time were varied as shown in Table 1 below. Both the electrodes 4 of the apparatuses shown in Figs. 21a and 21b had a treating surface area of 6,000 cm². Exp. No. Conditions L-value Output (W) Treating time (min.) Untreated - - 12.5 a-1 1,500 1 9.1 a-2 " 2 6.56 a-3 " 3 6.32 a-4 " 4 6.17 a-5 2,000 1 8.09 a-6 " 2 6.35 a-7 " 3 6.09 a-8 " 4 5.95 b-1 1,500 1 12.3 b-2 " 2 12.0 b-3 " 3 11.7 b-4 " 4 11.5 b-5 " 10 10.3 b-6 2,000 1 12.2 b-7 " 2 11.8 b-8 " 3 11.5 b-9 " 4 11.2 b-10 " 10 10.1 In the resultant fabrics, portions having a higher etching rate, namely, the partially fluorinated acrylic resin phases, were predominantly etched to form pits and recesses. In Fig. 22, an interrelation of the treating time and the color deepness (L-value) of the etched fabrics are shown. As is clear from Table 1, it has been demonstrated that the apparatus of the present invention functions remarkably excellently in plasma etching as compared with the conventional apparatus. Example 2 Onto the black dyed georgette fabric obtained in Example 1, an aqueous dispersion liquid of a mixture of amino modified silicone resin and partially fluorinated acrylic resin with a mixing ratio of 1:1 which had good mutual miscibility and mutual incompatibility, showing micro-phase separation, was applied to an amount, as resin, of 1% o.w.f. by soaking according to a conventional process. After drying, the fabric was heat-treated at 150°C to fix the resins. Then the fabric was subjected to etching treatment with low-temperature gas plasma under the following conditions. The fabric was attached onto an antenna electrode 50 mm high, 1,200 mm long and 400 mm wide, made of aluminum plate and filled with polyester resin having closed cells of an average cell diameter of 3 mm or less. After evacuating the vacuum vessel to 1,33 Pa (10⁻² torr), the pressure was adjusted to 40 Pa (0.3 torr) by introducing O₂ gas therein. Then a high frequency of 13.56 MHz was applied with an output of 0.2 W per cm² of the antenna electrode surface area to treat the fabric with plasma. For comparative purposes, the the fabric was treated in the same manner, except that electrodes having no filling materials inside were used. In Table 2, weight losses by etching (ΔW) and the color deepness (L-values) of the treated fabrics, when the treating time was varied, are shown. Examples 3-8 Four minutes plasma treatment was carried out in the same manner as Example 2 above, except that filling materials shown in Table 3 were used for the antenna electrodes. The result is shown in Table 3. Example No. Filling material Weight loss (Δw) (%) Color deepness (L-value) Electrode surface temperature (°C) 3 Porous glass 0.60 9.7 37 4 Phenolic resin 0.58 9.8 38 5 Silicone rubber 0.62 9.5 36 6 Aluminum 0.60 9.6 37 7 Porous alumina 0.61 9.7 37 8 Diatomite 0.59 9.7 39 As demonstrated above, in the apparatus of the present invention, all the distances from the electric power introducing member to the antenna electrodes can be equalized, so that the electric power of the same phase can be applied to the plurality of antenna electrodes. Additionally, since all of the electric power introducing members for the respective electrodes have been unified, a singular electric source is enough. Therefore, mutual interference of plasma among a plurality of electrodes and mutual interference among a plurality of electric sources, as seen in the conventional plasma treatment apparatuses having multilayered electrodes, can be prevented, resulting in stable operations and stable qualities. Additionally, in the apparatus of the present invention, the space around the antenna electrodes is so narrow as compared with conventional apparatuses that useless plasma discharges at this portion are decreased with efficient use of input electric power. Particularly, in the apparatus comprising a plasma treatment chamber having the limited space inside, since the electric power can be introduced from the electric power introducing member in the limited space to the antenna electrodes along the shortest paths via the electrode connecting members. Accordingly, hitherto experienced disadvantages, such as useless discharges outside an effective plasma treatment space, for example, discharges between electrode connecting members damages of structural components or parts caused thereby or the like are mitigated to the utmost. Additionally, in the case where the electrodes partly provided with insulating surfaces are employed, the insulating surfaces formed with appropriate arrangements and dimensions effectively prevent abnormal plasma discharges which are otherwise caused by high electric potential concentrated towards the end edges of the electrodes when the treating material is drawn onto or pulled off from the surfaces of the electrode at a certain angle. Thus, even when the plasma input is large, defects caused by abnormal treatment and abnormal discharges etc. will not be formed, and uniform treatment can be effected. Accordingly, a large output power can be applied to thereby increase the treating rate and effect, and treated materials of uniform quality can be obtained, so that yield is largely improved. Further, in the case where the electrodes densely filled with filling materials or having a uniform, continuous, monolithic surface are employed, useless discharges inside the antenna electrodes can be prevented to increase discharge efficiency between the antenna electrodes and the grounded electrodes and stabilize the plasma discharges. This fact functions synergetically with the increase in the treating rate effectible by a power increase, and brings about remarkable increases in treating efficiency. Furthermore, the covers provided on the grounded electrodes allow fresh gases to be efficiently fed and decomposed gases to be efficiently discharged, so that the plasma treatment can always be conducted at a constant gas ratio and the bad influence of the decomposed gases can be prevented. Thus, the apparatus of the present invention is more excellent than conventional apparatuses with respect to increases in efficiency, uniformity and stability of the plasma treatment. As explained above, according to the present invention, apparatuses for plasma treatment as well as articles treated therewith of high quality and high stability can be provided at remarkably low cost.

Claims: An apparatus for continuous plasma treatment of long, flat materials comprising a plasma treatment chamber (A), an electric power introducing member (1) positioned in the central portion of said plasma treatment chamber (A), a plurality of antenna electrodes (4) arranged radially extending from the vicinity of said electric power introducing member (1), the electric power introducing member (1) being connected by means of a respective electrode connecting member with the respective end of each antenna electrode (4) which is closer to the electric power introducing member (1), a plurality of grounded electrodes (5) arranged each facing a treating surface of said antenna electrodes (4), and a guide means for passing treating materials (8) through gaps between said antenna electrodes (4) and grounded electrodes (5). An apparatus as claimed in claim 1, wherein said antenna electrodes (4) have curved treating surfaces bulging out with respect to the direction of the travel of the treating materials (8). An apparatus as claimed in claim 1, wherein said antenna electrodes (4) have flat treating surfaces. An apparatus as claimed in claim 1, wherein said grounded electrodes (5) have treating surfaces bulging out with respect to the direction of the travel of the treating materials (8). An apparatus as claimed in claim 1, wherein said electric power introducing member (1) is enclosed in a limited space (27) defined by a surrounding wall (26) and communicating with an outer atmosphere, which electric power introducing member (1) is connected with said respective ends (28) of the antenna electrodes (4) through said surrounding wall (26) defining the limited space (27). An apparatus as claimed in claim 1, wherein said antenna electrodes (4) have surfaces formed from metal plates (102;103) and the inside filled with a filling material (105) to be dense enough substantially not to allow the plasma to be produced inside. An apparatus as claimed in claim 6, wherein said inside is densely filled with solid materials free from voids and cavities. An apparatus as claimed in claim 6, wherein said inside is filled with porous materials having voids or cavities with an average diameter of about 10 mm or less. An apparatus as claimed in claim 8, wherein said voids or cavities have an average diameter of about 5 mm or less. An apparatus as claimed in claim 8, wherein said porous materials are selected from the group consisting of metals, glasses, ceramics, synthetic high-polymers, resins and rubbers. An apparatus as claimed in claim 1, wherein at least either one group of said antenna electrodes (4) and grounded electrodes (5) are provided with a temperature control means. An apparatus as claimed in claim 1, wherein said antenna electrodes (4) and grounded electrodes (5) are arranged to space in parallel apart with each other. An apparatus as claimed in claim 2, wherein said guide means is arranged in a fashion that said treating materials (8) are brought into contact with surfaces of said antenna electrodes (4). An apparatus as claimed in claim 3, wherein said guide means is arranged in a fashion that said treating materials (8) are brought into contact with surfaces of said antenna electrodes (4). An apparatus as claimed in claim 4, wherein said guide means is arranged in a fashion that said treating materials (8) are brought into contact with surfaces of said grounded electrodes (5). An apparatus as claimed in any one of claims 13-15, wherein said guide means is a plurality of guide rolls (6;7;9;10;21;22) adjustable in fixing position. An apparatus as claimed in claim 1, wherein covers (14;14';14'') extending between both side edges and outer edges, respectively, of mutually adjacent two grounded electrodes (5,5') interposing an antenna electrode (4) therebetween are further provided to define a plasma treatment space between said mutually adjacent two grounded electrodes (5,5'') and gas feed orifices (11) and gas discharge orifices (12) are provided near one end and the other end, respectively, of the grounded electrode (5) in said plasma treating space. An apparatus as claimed in claim 17, wherein said gas feed orifices (11) are provided near the outer end with respect to the radial arrangement of the grounded electrodes (5). An apparatus as claimed in claim 13 or 14, wherein said antenna electrodes (4) have insulating layers (109) formed on the surface from the end of the electrodes (4) approached by said treating materials (8) up to the portion where said treating materials (8) just come into contact with the electrodes (4). An apparatus as claimed in claim 19, wherein said insulating layers (109) are formed on the surfaces further including the delivery end of the electrodes (4) up to the portion where said treating materials (8) are pulled off from the electrodes (4). An apparatus as claimed in claim 19 or 20, wherein said insulating layers (109) have a length of 1/4 or less of the length of said antenna electrodes (4). An apparatus as claimed in claim 1, wherein said plasma treatment chamber (A) further accommodates a feed roll (9) and a windup roll (10) for the treating materials (8). An apparatus as claimed in claim 1, wherein said plasma treatment chamber (A) communicates with a chamber (B;C) accommodating a feed roll (9) and a windup roll (10) for the treating materials (8). An apparatus as claimed in claim 1, wherein said plasma treatment chamber (A) communicates with two chambers (B;C) accommodating a feed roll (9) and a windup roll (10), separately. An apparatus as claimed in claim 13 or 14, wherein said antenna electrodes (4) have a smooth, uniform and continuous monolithic surface structure. An apparatus as claimed in claim 1, wherein said plasma treatment chamber (A) is provided on the periphery with at least one viewing port (30) through which a gap between said antenna electrode (4) and grounded electrodes (5) can be observed. An apparatus as claimed in claim 1, wherein said plasma treatment chamber (A) is further provided on the periphery with at least one hole (30) equipped with a closable and openable lid.

Inventors: KONDO YOSHIKAZU, TSUDA YUKIO, YAMAMOTO TOSHIHIRO, KONDO, YOSHIKAZU, TSUDA, YUKIO, YAMAMOTO, TOSHIHIRO
Applicants: KANEBO LTD, KANEBO, LTD.
Application year: 1988
Main classification: H01J37
IPC codes: D06M10, B29C59, H01J37, C23C16